U of G
FOOD 2010
Final EXAM
STUDY GUIDE
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Food Science Chapter Summaries
Winter Semester 2017
Dr. Massimo Marcone
Unit 1: Overview of Food Science
Parts of the Food Industry
• Note: These four divisions are artificial and they actually overlap one another.
1. Production- Includes such industries as farming, ranching, orchard management, fishing and
aquaculture. Technologies involved in production of the raw materials include the selection of
plant and animal varieties, cultivation, growth, harvest, slaughter, and the storage and handling of
the raw materials.
2. Manufacturing/processing- Converts raw agricultural products to more refined/finished products.
Manufacturing requires many unit operations and processes that are at the core of food technology.
3. Distribution- Aspects beneficial to product sales, including: product form, weight and bulk,
transportation, storage requirements, and storage stability.
4. Marketing- Selling of foods and involves wholesale, retail, institutions, and restaurants.
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Another way of dividing the food industry is along major product lines:
Cereals and bakery products
Meats, fish and poultry
Dairy products
Fruits and vegetables
Sugars and other sweets
Fats and oils
Nonalcoholic beverages/alcoholic beverages
Note: These divisions are typically where consumer consumption is measured and reported.
Trends
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The percentage of income spent for food has declined as a result of the income-inelastic nature of
the total demand for food: As income rises, the proportion spent for food declines.
The expenditures (spending) for food require a large share of income when income is relatively
low, in any country.
Americans spent only about 8% of their personal consumption expenditures for food to be eaten at
home. This compares with 10% for Canada and 11% for the United Kingdom. In less developed
countries, at-home food expenditures account for more than 50% of a household budget.
In relation to total per capita personal consumption expenditures, Americans spend the lowest % on
food. Factors other than income alone influence food expenditures in developed countries.
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An abundance of fertile land and a varied climate means that Americans do not have to rely as
heavily on imported foods. Also, the American farm-to-consumer distribution system is highly
successful at moving perishable foods over long distances with minimum spoilage. American
farmers also use a lot of agricultural information and state-of-the-art farming equipment. This
allows them to produce food efficiently.
Consumption trends change over the years, and this influences what the food industry does.
Demand for individual foods is more responsive to prices as consumers substitute among
alternative food products. Rising incomes increase expenditures on more expensive foods as
consumers demand more convenience and quality. Short-period changes in consumption reflect
mostly changes in supply rather than changes in consumer tastes. Additionally, changes in
household size and in age distribution of the population, can bring changes in consumption.
Better quality, increased variety, and year-round availability have boosted consumption of fresh
fruits and vegetables. Price, convenience, and increasing preference for fast food and ethnic food
has increased consumption of frozen vegetables and canned tomato products.
Away-from-home meals and snacks now capture almost half (45%) of the U.S. food dollar.
Fast food accounts for the largest and fastest rising share of sales in the food industry. Sales in fastfood industries now outpace the sales in full-service restaurants.
The top 5 restaurant chains in the U.S:
1. McDonald’s
2. Subway
3. Pizza Hut
4. Burger King
5. KFC
Consumers want to combine mealtime with time engaged in other activities such as shopping,
work, or travel. This is why many fast food chains are located within stores (ex. Wal-Mart).
The food industry represents some of the largest advertisers, and advertising through media plays
an important role in influencing food trends.
Allied Industries
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Allied industries are companies that do not sell food directly but they are deeply involved in the
food industry. Allied industries produce nonfood items that are necessary for marketing food.
An example of an allied industry is the packaging industry, which provides cans, food colour,
flavor, plastic and paper products.
Another example is the chemical manufacturers, which supply preservatives, enzymes, stabilizers,
acidulants, and other chemicals used in foods.
Food machinery and equipment manufacturers are another aspect of the allied industries. They
develop microwaves, pasteurizers, evaporators, infrared cookers, liquid nitrogen freezers, freezedrying systems and computer controls.
Additionally, keeping food supplies safe and keeping consumers informed requires monitoring and
regulatory agencies (ex., FDA), lawyers, consumer action and information agencies, and other
regulatory agencies.
Vertical coordination (the way products are acquired or traded in a market) seems to be a way of
the future. Food industry firms form 3 basic types of vertical coordination:
1. Open production: A firm purchases a commodity from a producer at a market price
determined at the time of purchase.
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2. Contract production: A firm commits to purchase a commodity from a producer at a price
formula established in advance of the purchase.
3. Vertical integration: A single firm controls the flow of a commodity across two or more
stages of food production.
The food industry has traditionally operated in an open production system. However, more
selective consumers and new technological developments that allow farm product separation, are
contributing to a decrease in open production and an increase in contract production and vertical
integration. Changing demographics and increasing value of a person’s time are fueling this trend
and are contributing to consumer preferences for a wide variety of food products.
Providing food products with specific characteristics preferred by more selective consumers will
involve increasingly more detailed raw material products, such as a frying chicken with a specific
weight/size. Carefully tailoring raw materials with processing is also accompanied by changes in
vertical coordination.
International Activities
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The U.S. accounts for about ¼ of the industrialized world’s total production of processed foods.
6/10 and 21/50 largest food processing firms in the world are headquartered in the U.S.
U.S. food brands are well received internationally and often accepted as local brands.
The U.S. processed foods market is global in scope, considering:
1. Combination of imports and exports of foods and food ingredients
2. Foreign production by U.S. food firms
3. Host production by foreign food firms
4. Other international commercial strategies
In terms of international trade, the processed foods sector surpasses agricultural products by a
considerable margin.
The top 5 world’s largest food processing firms include:
1. Nestle S.A.
2. Kraft Foods/Philip Morris
3. Unilever
4. ConAgra
5. Pepsico
World trade imports represent products not grown in the U.S: Coffee, tea, cocoa, and spices.
The U.S. is the largest exporter of cereal grains and soybeans, as their worldwide demand
increased.
The recent trends to decrease trade tariffs (tax), and improvements in transportation and
communication, have stimulated international activities in the food industry.
National infrastructure policies affect the ability of a nation’s firms to pursue global marketing
strategies.
Technical innovations in the interconnected communication and transportation sectors:
1. Enhances efficiency in the production and distribution of processed foods
2. Improves managerial control and responsiveness
3. Helps identify and fulfill new commercial opportunities
In the U.S., international commercial gains in processed foods happen when policies that reduce
government control in the above sectors and that have encouraged evolution of competitive
communications and transportation industries are introduced.
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Responsiveness to Change
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Per capita food consumption- total food consumed by each individual.
Per capita food consumption changes little from year to year.
The types of foods consumed change continually, contributing to competition and making the
industry change frequently. Over 10,000 new food products are introduced each year.
The kinds of foods people eat change in response to:
1. Demographic shifts
2. Supply of ingredients
3. Availability and costs of energy
4. Politics
5. Scientific advances in nutrition, health and food safety
6. Changes in lifestyle
The industry is required to respond according to changes such as:
1. Attitudes toward foods (ex., changing attitudes towards fat, cholesterol, fiber, etc.)
2. Changes in government regulation of food additives, food composition standards, and
labeling
3. Technical innovations such as ingredient modifications, new processing methods, new
packaging methods, and cooking advances
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Interrelated Operations
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The food industry is a systematic and rhythmic process. Throughout all divisions, costs and
availability are carefully monitored and controlled.
Since the food industry is high-volume, low-markup (ex., Costco, Sam’s Club), small losses
anywhere along the chain can mean large losses to the food producer.
Any trend towards contract production and vertical integration, as opposed to open production,
implies that firms at one stage of production exert more control over the quality of output at other
stages. For instance, pasta producers may gain control over decisions previously made by farmers,
in order to get a specific type of wheat, and in turn compensate the farmers through bonuses for
quality.
Recent changes in vertical coordination (methods used to manage vertical stages in marketing)
have been accompanied by an increase in concentration in the food sector. These developments
have raised 2 policy concerns:
1. Market power in the processing sector
2. Environmental protection
Food is now a global commodity due to changes in export/import laws, transportation, and
processing and communication.
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Unit 2: Regulation and Labeling
Federal, Food, Drug, and Cosmetic Act
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The U.S Food and Drug Administration (FDA) operating under the federal Food, Drug, and
Cosmetic Act, regulates the labeling for all food besides meat and poultry.
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The U.S Department of Agriculture (USDA) regulates meat and poultry products under the
federal Meat Inspection Act.
Additional Food Laws
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The Federal Meat Inspection Act of 1906 provides for mandatory inspection of animals,
slaughtering conditions and meat processing facilities. The Food Safety and Inspection Services
(FSIS) of the USDA enforces the act.
Federal Poultry Products Inspection Act of 1957 works the same as the Meat Inspection Act, but
it applies to poultry and poultry products
Federal Trade Commission Act was modified in 1938 to protect the public and the food industry
against false advertising.
Infant Health Formula Act of 1980 provides that manufactured formulas contain the known
essential nutrients at the correct levels.
Nutrition Labeling and Education Act of 1990 protects consumers against partial truths, mixed
messages, and fraud regarding nutrition information.
Legal Categories of Food Substances
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In the U.S., substances that become a part of food is legally divided into several categories:
“Generally recognized as safe” (GRAS): substances added to foods that have a history of being
safe
o Includes common spices, natural seasonings, baking powders, many flavourings,
etc.
Food Additives: specific group of substances that are added intentionally and directly to foods
o These are regulated and approved by FDA
o The additive must be harmless in the intended food application and intended level
of use
o Additives fall into one of the following categories:
◙ Preservatives
◙ Antioxidants
◙ Flavouring agents
◙ Sweeteners
◙ Emulsifiers, stabilizers, and thickeners
◙ Leavening agents
◙ Anticaking agents
◙ Humectants (used to reduce loss of moisture)
◙ Bleaches
◙ Acids, bases, and buffers
◙ Nutrients
Testing for Safety
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Pesticides, herbicides, chemical additives, and spoilage are of concern, but the microbiological
quality is the main focus for food scientists, processors and consumers.
Micro organisms are often too small to be seen with the naked eye and they are able to
reproduce rapidly
Many of them can produce toxins and cause infections
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E. coli is commonly employed as an indicator microorganism. It is a coliform bacterium
common to intestinal tract of humans and animals.
Total counts of microorganisms are also an indication of the sanitary quality of the food. This is
called the Standard Plate Count (SPC).
o The total count of viable microbes reflects the handling history, state of
decomposition, or degree of freshness of the food.
o Most foods have standards of limits for total counts
o A low SPC doesn’t always mean a safe product
Quality Assurance (QA)
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Incoming raw and finished milk products are continually monitored to ensure compliance with
compositional standards, microbiological standards, and various government regulations. A QA
manager can halt production, refuse raw material, or stop the shipments if the specifications for a
product are not met. This department doesn’t not normally have control over the product unless
something has gone wrong.
The major functions of the QA include:
Compliance with specifications: legal requirements, industry standards, internal company
standards, shelf-life tests, customer’s specifications
Test procedures: testing of raw materials, finished products, and in process tests
Sampling schedules: use a suitable sampling schedule to maximize probability of detection
while minimizing workload
Records and reporting: maintain all QA records so that customer complaints and legal problems
can be dealt with
Troubleshooting: solve various problems caused by poor quality raw materials, unpredictable
supplies and malfunctioning process equipment. As well as investigate reasons for poor quality
to avoid repetition.
Special problems: customer complaints, production problems, personnel training, etc.
A typical QA department has a chemistry lab, raw materials inspection lab, sensory lab, and a
microbiology lab.
Food Labeling
Most food products sold must have the product name, manufacturer’s name and address, the
amount of product in package, and the product ingredients. Ingredients are listed in descending
order based on their weight. Fresh fruit, veggies, and meat are excluded from these labeling
requirements.
In 1973 the FDA established “nutrition labeling” or guidelines for labeling the nutrient and
caloric content of foods. It is only mandatory for foods that have nutrients added or make a
nutritional claim.
- Current nutrition labeling regulations from the FDA require a label and have a percentage of the
U.S. Recommended Daily Allowance (U.S. RDA)
*Note: U.S. RDA is not the same as RDA (Recommended Dietary Allowances)! *
o For each nutrient, the U.S. RDA is the highest RDA for any of the RDA age and
sex groups. The U.S. RDA usually apply to people four years of age and older.
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Labels must also include serving size; serving per container; calories per serving; grams of
protein, carbohydrate, and fat per serving. As well as the percent of the U.S. RDA for protein, 5
vitamins, and 2 minerals
- There is less nutrition information on labels regulated by the USDA. USDA labels list only
serving size; serving per container; calories per serving; grams of protein, carbohydrate, and fat
per serving.
New Food Labels
In the 1990 Food Marketing Institute (FMI) survey, over 70% of food shoppers identified
taste, nutrition, and product safety as very important factors in making food purchases. In the
same survey, 36% said they always read the ingredients and nutrition labels while 45% said that
they sometimes read the labels.
Consumer demand of clearer and easier to understand information led to the passage of the
Nutrition Labelling and Education Act (NLEA) of 1990.
The New Food Label
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Key features of the new label includes:
Nutrition labeling for almost all foods
Distinctive, easy to read format
Information on the amount per serving of saturated fat, cholesterol, dietary fiber, and other
nutrients
Nutrient reference values, expressed as Percentage Daily Values
Uniform definitions for terms that describe a food’s nutrient content like light, low-fat, and high
fiber
Claims about the relationship between a nutrient or food and a disease (or health related
condition)
Standardized serving sizes
Declaration of total percentage of juice in juice drinks
Voluntary nutrition information for many raw foods
Foods Affected
The regulations call for nutrition labeling for most foods. Voluntary programs for nutrition
information were also set up for many raw foods: the 20 most frequently eaten raw fruits,
vegetables, fish and the 45 best selling cuts of mean. Each are under FDA’s voluntary point of
purchase nutrition information program.
Exemptions from Nutrition Labeling
- Foods served for immediate consumption, such as in hospital cafeterias and airplanes, and those
sold by food service vendors, such as mall cookie counters, sidewalk vendors, and vending
machines
- Ready to eat food that is not for immediate consumption but is prepared primarily on site (ex.
Bakery, deli, candy store items)
- Food shipped in bulk, as long as it’s not for sale in that form to consumers
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Medical foods, such as those used to address the nutritional needs of patients with certain
diseases
- Plain coffee/tea, some spices, and other foods that do not have any significant amounts of
nutrients
- Food produced by small businesses, based on the number of employees
However, these foods are still able to carry nutrition information when appropriate, as long as it
follows the new regulations. Exemption will be lost if their labels carry a nutrient content or
health claim.
Nutritional information on game meats is not required on individual packages, instead can be given
on counter cards, signs, or other point of purchase materials.
Nutrition Panel Title
A new title called “Nutritional Facts” has replaced “Nutrition Information Per Serving”. There are
also requirements for type size, style, spacing, and contrast to ensure an easier to read label.
Serving Sizes
Are not more uniform and reflect the amounts people actually eat. They must also express in both
common household and metric (g and ml) measures. The serving sizes that appear on food labels
are based on FDA- established lists of “Reference Amounts Customarily Consumed Per Eating
Occasion.”
Nutrition Information
The following is the order they must appear on the label:
- Total calories
- Calories from fat
- Calories from saturated fat
- Total fat
Saturated fat
- Polyunsaturated fat
- Monounsaturated fat
- Cholesterol
- Sodium
- Potassium
- Total carbohydrate
- Dietary fiber
- Soluble fiber
- Insoluble fiber
- Sugars
- Sugar alcohol (sugar substitutes)
- Other carbohydrates
- Protein
- Vitamin A
- Percent of vitamin A present as beta- carotene
- Vitamin C
- Calcium
- Iron
- Other essential vitamins and minerals
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These are the only components that are allowed on the nutritional panel. If a claim is made about any
of the optional components or if a food is fortified/enriched with any optional component, the
nutritional information for these components becomes mandatory.
Daily Values (DRVs)
- The new label reference value, Daily Value, comprises two sets of dietary standards: Daily
Reference Values (DRVs) and Reference Daily Intakes (RDIs)
o Only DRVs appear on label though
- DRVs represent macronutrients that are sources of energy that do not contribute to calories (ex.
Fat, carbohydrates, protein)
- DRVs for the energy producing nutrients are based on the number of calories consumed per day
- Due to current health recommendations, DRVs for some nutrients represent the uppermost limit
that is considered desirable
Nutrient Content Descriptions
Terms that can be used to describe the level of nutrient in a food and how they can be used...
- Free: products contain no amount, or a trivial amount of fat, saturated fat, cholesterol, sodium,
sugars and calories. Synonyms are “without”, “no” and “zero”
- Low: can be used for foods that can be eaten frequently without exceeding dietary guidelines for
one or more of these components- fat, saturated fat, cholesterol, sodium, sugars and calories
- Lean and Extra Lean: used to describe the fat content of meat, poultry, seafood and game
meats
- High: used for food that contains 20% or more of the Daily Value for a particular nutrient in a
serving
- Good Source: one serving of food contains 10-19% of Daily Value for a particular nutrient
- Reduced: that a nutritionally altered product contains at least 25% less of a nutrient or of
calories than the regular product
- Less: a food, altered or not, contains 25% less of a nutrient or of calories than the reference food
- Light (can mean two things): first, a nutritionally altered product that contains 1/3 fewer
calories or half the fat of the reference food. Second, the sodium content of a low calorie, low fat
food has been reduced by 50%
- More: a serving of food, whether altered or not, contains a nutrient that is at least 10% of the
Daily Value more than the reference food
Other Definitions
- Percent Fat Free: must be a low fat or fat free product. Claim must also reflect the amount of
fat present in 100 grams of the food.
- Implied: these claims are prohibited when they wrongfully imply that a food contains or does
not contain a meaningful level of a nutrient.
- Healthy: must be low in fat and saturated fat, as well as have limited amounts of cholesterol
and sodium.
- Fresh: only can be used to suggest that a food is raw, never been frozen or heated, and contains
no preservatives (but irradiation at low levels is allowed). “Freshly frozen” can be used for foods
that are quickly frozen while still fresh. Blanching is also allowed.
USDA’s Meat Grading Program
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USDA has quality grades for beef, veal, lamb, yearling mutton, mutton, and pork. However, USDA
does not carry through the grades for pork to the retail level like the other meats.
USDA meat grades are based on nationally uniform Federal standards of quality. They are applied
by experienced USDA graders that interpret and apply the standards in a uniform manner
throughout the country. When meat is graded, a shield shaped purple mark is stamped on the
carcass. Nowadays, you don’t see the purple mark on meat cuts at the store but the retailers will
put stickers with the USDA grade shield on packages of meat.
Health Claims
Claims for eight relationships between a nutrient or a food and the risk of a disease or health- related
condition are now allowed. The claim must meet the requirements for authorized health claims,
and must be stated in a way that consumers can understand the relationships. The allowed
nutrient- disease relationship claims include:
- Calcium and osteoporosis
- Fat and cancer
- Saturated fat and cholesterol and coronary heart disease (CHD)
- Fiber- containing grain products, fruits and vegetables and cancer
- Fruits, vegetables, and grain products that contain fiber and risk of CHD
- Sodium and hypertension (high blood pressure)
- Fruits and vegetables and cancer
- Folic acid and neural tube defects
Ingredient Labeling
Ingredient declaration is now required on all foods that have more than one ingredient. The
ingredient list includes, when appropriate:
- FDA certified color additives, such as FD&C Blue No.1, by name
- Sources of protein hydrolysates, which are used in many foods as flavours and flavour
enhancers
- Declaration of caseinate as a milk derivative in the ingredient list of foods that claim to be nondairy, such as coffee whiteners
Main reason for these requirements is that some people may be allergic to such additives and now
will be able to better avoid them.
All beverages that claim to contain juice must state the total percentage of juice on the information
panel.
Unit 3: Food Chemistry: Macro & Micro Components
Review of Chemistry
Elements
Atom = smallest unit of an element that still exhibits properties of the element ; consist nucleus
with protons and neutrons surrounded by electrons.
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In its neutral elemental state # of protons = # of electrons
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Electrons travel in orbit around nucleus in different energy levels. Specifically filled with
2 in the first, eight in the second, and so on.
Atomic number = # of protons
Atomic weight = # protons + # neutrons
Chemical properties of an element are determined by number of electrons in outermost energy
level of an atom. This is what interacts with other atoms when two + atoms come together.
Chemical Bonds
Covalent Bonds:
• Strongest chemical bonds
• Formed by the sharing of a pair of electrons
• Once formed, rarely break spontaneously -- thermal energy of a molecule at room temp is
much lower than the energy required to break a covalent bond
• Can be single, double or triple
• Carbon-Carbon are unusually strong and stable covalent bonds
• Can have partial charges when atoms involved have different electronegativity
• Delta - and delta + used to indicate partial charges
Hydrogen Bonds:
• Consequence of partial charges
• Formed when hydrogen atom is shared between 2 molecules
• Have polarity -- hydrogen atom covalently attached to a very electronegative atom (N,
O, or P) shares its partial positive charge with a second electronegative atom (N, O, or P)
• Example: hydrogen between two water molecules
• Frequently found in proteins (amino acids in polypeptide chains are hydrogen-bonded
together) and nucleic acids (G and C in DNA or RNA are hydrogen-bonded together) -serve to keep protein structure secure
Ionic Bonds:
• Formed when there is a complete transfer of electrons from one atom to another, resulting
in two ions, one + charged and the other - charged
• Example: Sodium chloride = Na+ClVan der Waals Bonds:
• Very weak bonds formed between nonpolar molecules or nonpolar parts of a molecule
• Created because a C-H bond can have a transient dipole and induce a transient dipole in
another C-H bond
Molecules
Smallest identifiable unit into which a pure substance can be divided and still retain the
composition and chemical properties of that substance.
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Held together by shared electron pairs, or covalent bonds -- atoms adopt specific positions
relative to one another so as to maximize strength of bond.
Molecular weight of molecule= sum of atomic weights of its component atoms
If substance has molecular weight of 32, then 32 grams = 1 mole of that substance.
Ie. NaCl has molecular weight of 58.5 (23 +35.5) and one mole of NaCl weighs 58.5 grams.
Reactions
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Chemical changes can be classified as electron-transfer or oxidation-reduction reactions
Oxidation = addition of oxygen
4Fe + 3O → 2Fe O
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Reduction = removal of oxygen
2Fe2O3 +3C → 3CO2 +4Fe
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Oxidation numbers used to describe “electrical state” of the atom; defined as sum of
negative and positive charges in an atom. Since every atom contains equal + and charges, oxidation number of any atom is always zero.
Oxid-red. Reactions always involve a change in the oxidation state of atoms or ions
involved
Loss of electrons = + oxidation state
Gain of electrons = - oxidation state
Metabolism
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Defined as: all chemical reactions that occur in a living system
Divided into anabolism (synthesis of compounds) and catabolism (breakdown of
compounds)
Anabolic primarily characterized as reduction reactions and Catabolic are primarily
oxidation reactions
Organic Chemistry
Involves carbon-containing molecules and all carbon atoms have 4 bonds to account for.
In carbohydrates, fats, and proteins, each carbon can connect to:
• Another carbon (C)
• A hydroxyl (OH - ie. alcohol)
• A hydrogen (H)
• An amino group (NH2)
• An oxygen (double bond) (O)
Chemistry of Foods
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Nutrients are naturally occurring chemical substances found in food.
Six categories = proteins, lipids, carbohydrates, vitamins, minerals, and water
Proteins, fats and carbohydrates provide energy for our bodies measured by kilocalories
(kcal)
o Each gram of protein or carbohydrate has 4 kcal energy
o Each gram of fat has 9 kcal energy
Carbohydrates
- Come from plant foods
- Simple carbs = monosaccharides and disaccharides
- Complex carbs = polysaccharides (include starches and dietary fibre)
- Composition = C (h O)
- Provides energy
- 4 kilocalories per gram
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Function in food
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Flavour enhancing
Water binding
Texture (starch, gluten)
Hygroscopic natures/water absorption
Source of yeast food
Regulating gelation of pectin dispersing molecules of protein or starch
Acting to subdivide shortening for creaming control crystallization
Preventing spoilage
Delaying coagulation protein
Giving structure to crystals
Affecting osmosis
Affecting colour or fruits
Affecting texture (viscosity, structure)
Contributing flavour other than sweetness
Monosaccharide:
6 carbons = hexose (ex: glucose, dextrose, fructose, galalctose)
5 carbons = pentose (ex: ribose and deoxyribose)
Disaccharide:
Two monosaccharides that are linked via removal of water (dehydration) and broken via
addition of water (hydrolysis)
Sucrose = glucose + fructose
Lactose = glucose + galactose
Maltose = glucose + glucose
Sugars in foods:
Sensory characteristics = colour, texture and flavour
Major role as sweetener or in texture development
Contribute to colour via caramelization and Maillard reaction
Honey, sorghum/molasses, maple syrup and selected fruit juice/pulps are sweetener substitutes
for cane and beet sugar
Processing cane sugar and beet sugar produces granulated, brown and liquid sugar
Sugar based sweeteners are those developed from corn starch
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Inversion of sugars:
Refers to hydrolysis of sucrose into fructose and glucose (may be called invert sugars)
Fructose and glucose are more hygroscopic than sucrose and enhance browning
Can take place in presence of acid or enzyme
Any product with an acid compound can cause hydrolysis of sugars
Caramelization
Application of heat to the point that sugars break down and polymerize
Reaction attributed to a range of browning reactions and flavour development
Sugars have various caramelization temps
Crystallization:
Can cause problems… for example in crystallization of lactose will make non fat milk difficult
to disperse ie: cause of gritty texture in frozen dessert
Candies divided into crystalline and non crystalline
Crystalline = fudge, fondant and any candy in which crystals are an important structural
component
Non crystalline = caramels, brittles, taffy
Rate of crystallization = speed at which nuclei grow into crystals
Dependant on concentration of solute because higher concentration will crystalize more rapidly
Dependant on temp because in lower temps will crystalize more rapidly
Fat and protein decrease number and size of crystals
Polysaccharides:
Combination of more than two sugars = oligosaccharide
If very large = polysaccharide
Raffinose (glucose, fructose and galactose) and stachyose (same as Raffinose except with two
galactose) are of interest because they are hard to digest
May be added to foods to increase dietary fibre
Can be added to thicken, form gels, bind water and stabilize proteins ex: starch
Some polysaccharides are naturally occurring, such as cellulose, starch, agar, pectin, guar gum
Starch:
Glucose molecules linked in long chain (500 to several hundred thousand)
Storage form of energy for plants
Glycogen is storage form of energy for animals
Starch exists are crystalline granules
Two types are amylose and amylopectin
Amylose contributes to gel formation (linear chains)
Amylopectin contributes to viscosity (branched chains)
In temperatures higher than 60-70 degrees Celsius, irreversible swelling occurs as granules
absorb waster, known as gelatinization
Loss of birefringence occurs at time of rapid gelatinization and is therefore a good indication of
initial gelatinization temp of a given starch
Range refers to temp range over which all granules are fully swollen
Cellulose:
Most common polysaccharide and major component of plant cell wall
Polymer of glucose molecules linked by 1 to 4 linkages
Cannot be digested by humans
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-
Pectin is a polymer of galacturonic acid and not digested (cements cells together in plants)
Complex carbs that cannot be digested are generally called fibre
Fibre may help reduce cholesterol by binding to it and making it unavailable for absorption
Proteins
-
- Polymers of amino acids
Needed for building and repair of body tissue and metabolic function
Has a primary, secondary, tertiary and quaternary structure
Must be broken down (hydrolyzed) into amino acids before being absorbed/used
Once absorbed they are used to make proteins, converted to energy, or stored as fat
20% of human body is made up of protein
Functions:
Enzymes such as trypsin and pepsin
Storage such as ovalbumin and ferritin
Transport such as haemoglobin and lipoproteins
Contractile such as actin and myosin
Protective such as antibodies and thrombin
Hormones such as insulin and growth hormone
Structural such as keratin, collagen and elastin
Membranes
Amino Acids:
-
-
Contain amino group (NH ) and acid group (COOH)
20 are found in proteins
Joined by forming peptide bonds (condensation of amino group on one with the acid group on
another)
Broken via hydrolysis (addition of water)
Peptide bonds are not easily broken (cooking will not usually break the bonds)
2
Primary structure:
Sequence of a chain of amino acids linked by peptide bonds
Secondary structure:
Sequence of amino acids that are linked by hydrogen bonds between the carboxyl and amide
groups of the peptide bonds
Forms a pleated sheet or helix structure
Tertiary structure:
Occurs when attractions are present between alpha helices and pleated sheet
Involves the folding of the coiled chains
Involves covalent and hydrogen bonds and Van der Waals forces
Function of protein in foods
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-
Are amphophylic meaning they have polar (hydrophilic) and non-polar (hydrophobic) side
chains within one molecule
COLOUR: Biggest role through Maillard browning reaction (reaction between sugars and
proteins) seen in many baked goods. Also, selected colour pigments such as chlorophyll are
bound in chloroplasts in a protein-lipid matrix
TEXTURE: Example – in custards, protein gel strength is influenced by ovalbumin
denaturation. Also, in yogurt texture is influenced by gelation of casein.
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-
FLAVOUR: Not clear cut… Amino acids may contribute bitterness, sweetness and other
flavours.
Lipids
•
•
•
Includes fats and oils from plants and animals (cholesterol = fat found only in animals)
Substance in foods that are soluble in organic solvents
Includes: triglycerides, fatty acids, phospholipids, some pigments, some vitamins, and
cholesterol.
Roles of Fats in Foods:
• Provide source of essential fatty acids, add caloric density (energy), act as carriers for
flavours, carry fat-soluble vitamins, contribute to texture and mouthfeel, precursors for
flavours and provide heat transfer medium (ie. in frying)
Fatty Acids (FAs):
• Naturally occurring FAs have even number of carbons
• Short-chain FAs -- important as odors
• Longer-chain FAs -- not volatile and do not contribute much to flavour
• Saturated vs. unsaturated
o Saturated = no double bonds
o unsaturated = one or more double bonds (forming a rigid kink in the hydrocarbon
tail)
• Common fatty acids = Stearic Acid (c18), Palmitic Acid (C16), Oleic Acid (C18 unsaturated due to presence of double bone)
Double Bonds:
• Fatty acids that contain double bonds = unsaturated
o Contain only one double = mono-unsaturated
o Contain 2+ double bonds = polyunsaturated
• Unsaturated can exist in two forms → cis or trans
o cis = naturally occurring FAs
• Double bonds in lipids are very reactive towards oxygen = Lipid Oxidation
o Products of lipid oxidation have very undesirable flavours; termed rancidity
o Some food additives specifically function to inhibit this lipid oxidation =
Antioxidants
o Examples: Butylated hydroxytoulene (BHT)
Butylated hydroxy anisole (BHA)
Vitamin C
Vitamin E
Triglycerides (TGs):
• Food molecules made up of: 3 FA molecules + glycerol molecule
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•
•
•
Majority of foods we consume contain fat in form of TGs
Broken apart by enzymes called lipases
Products of lipolysis often have soapy flavours
o Used in food industry as emulsifiers
o Triglyceride molecule that has one FA removed = diglyceride
o Triglyceride molecule that has 2 FA removed = monoglycerid
o Both di- and mono-glycerides used as emulsifiers
Phospholipids:
• FA connects to glycerol molecules that contain a molecule of phosphorus
• Play important role in body but are not essential nutrients (can be synthesized by both in
adequate quantities)
• Best known phospholipid = Lecithin
Cholesterol:
• Compound produced by body - has received a lot of attention due to link to heart disease
• Not an essential nutrient; body will produce all the cholesterol it needs, increased intake
from diet = decrease production by body (and vice versa)
• Making it difficult to decrease serum cholesterol by dietary means alone because body
will attempt to keep cholesterol supply constant
• Used by body for:
o Bile Salts
o Membrane structure
o Myelin Structure
o Vitamin D synthesis
o Steroid hormone synthesis
• Can have genetic problems that interfere with regulation of cholesterol synthesis, usually
leading to excessive production-- concern due t increased risk for coronary heart disease
Vitamins
Chemical compounds in food that are needed in very small amounts (milli- and micro-grams) to
regulate chemical reactions.
Fat-Soluble Vitamins:
1. Vitamin A - three active forms (retinOL, retinAL, and retinOIC ACID); most often found
in food in the form of retinOL; all 3 forms can be formed from the plant pigments
carotenes -- most common form is beta-carotene; susceptible to oxidation but relatively
heat stable
2.
Vitamin D - active form = cholecalciferol (Vitamin D3); produced from cholesterol by
action of UV (sunlight); also formed from a protovitamin; stored in Liver and functions in
absorption of minerals calcium and phosphorus; acts directly on bone and affects reabsorption of
calcium and phosphorus by the kidney
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3.
Vitamin E - also known as alpha-tocopherol; widely available in normal diet; functions to
detoxify oxidizing radicals that arise in metabolism, to stabalize cell membranes, to regulate
oxidation reactions and to protect vit. A and polyunsaturated FAs from oxidation
4.
Vitamin K - Dietary and intestinal bacterial sources contribute to supply of vit. K;
Storage in body is minimal; functions in normal blood clotting
Water-Soluble Vitamins:
1. Thiamin - functions in carbohydrate metabolism; makes ribose to form RNA; maintains
normal appetite and normal muscle tone in digestive tract
2.
Riboflavin- part of coenzyme involved in oxidation-reduction reactions in energy
production
3.
Niacin - component of 2 coenzymes (FAD and NADH) involved in oxidation-reduction
reactions releasing energy from food.
4.
Vitamin B6 - metabolism of amino acids and the conversion of glycogen to glucose
5.
Pantothenic Acid - part of coenzyme A (involved in synthesis and breakdown of fats,
carbohydrates and proteins); also part of fatty acid synthetase enzyme
6.
Folic Acid - coenzyme form of folic acid = tetrahydrofolic acid; functions in transfer of
formyl and hydroxymethyl groups; required for synthesis of purines and pyrimidines and for
efficient use of amino acid histidine
7.
Biotin - functions in fatty acid synthesis
8.
Cobalamin - also known as Vit. B12; required for nucleic acid synthesis, amino acid
synthesis, blood cell formation, neural function and growth; found only in animal products
9.
Vitamin C - also known as ascorbic acid; functions in wound healing, collagen synthesis,
iron absorption, and as an antioxidant; necessary for conversion of proline to hydroxyproline and
lysine to hydroxylysine; involved in conversion of amino acids to neurotransmitters; least stable
of all vits; oxidizes readily in light or air, when heated, or in alkaline solutions; degradations is
enhanced by presence of copper and iron.
Minerals
Needed in our bodies in very small amounts with various functions -- chemical reactions, body
structures, energy transfer, integral part of vitamins, hormones, and amino acids. Depending on
amount they are considered macrominerals or microminerals
Macrominerals:
1. Calcium (Ca) - involved in homeostasis; functions in blood clotting mechanisms, muscle
contractions; bone formation and resorption
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2.
Phosphorus (P) - makes up 14-17% of our skeleton; required for many energy-transfer
reactions; synthesis of some lipids and proteins
3.
Potassium (K) - maintains acid-base balance and osmotic pressure inside cells
4.
Sodium (Na) - maintains acid-base balance outside the cells and regulates osmosis of
body fluids; involved in nerve function and muscle function
5.
Chloride (Cl) - normally accompanies sodium in diet as NaCl (Salt); important
extracellular anion (- charge) involved in acid-base balance and osmotic regulation; essential
component of bile, hydrochloric acid and gastric secretions
6.
Magnesium (Mg) - more than half of Mg found in body is in the skeleton; activator of
enzymes
7.
Sulfur (S) - component of many biochemicals in body, ie, amino acids, biotin, thiamin,
insulin, chondroitin sulfate
Microminerals:
1. Chromium (Cr) - essential for humans; involved in glucose tolerance, stimulation of FA
synthesis, insulin metabolism, and protein digestion
2.
Cobalt (Co) - part of Vit B12 structure (found right in middle); Microflora in cecum and
colon use dietary cobalt to make B12
3.
Copper (Cu) - essential for several copper-dependent enzymes
4.
Fluorine (F) - involved in bone and teeth development
5.
Iodine (I) - essential for production of thyroid hormones (T3 and T4); these hormones
regulate basal metabolism
6.
Iron (Fe) - about 60% of iron is in red blood cells and 20% in muscles, in the body
7.
Manganese (Mn) - necessary for carbohydrate and fat metabolism; synthesis of cartilage
8.
Molybdenum (Mo) - part of enzyme xanthine oxidase
9.
Nickel (Ni) - associated with protein nickeloplasmin; essential for chickens
10.
Selenium (Se) - essential for detoxification of certain peroxides that are toxic to cell
membranes; closely connected with Vit. E working together to scavenge free radicals
(antioxidant functions)
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11.
Silicon (Si) - essential in young chickens; important in bone development and required in
very small amounts for humans
12.
Tin (Sn) - possible required by humans; shown to have growth promoting effects in rats;
no requirement known for humans
13.
Vanadium (V) - shown to be essential in rats; in chickens it increase growth rate
hematocrit; likely small amount required in humans
14.
Zinc (Zn) - component of many enzymes
Cadmium (Cd), boron (B), and aluminum (Al) also considered microminerals.
Water
•
•
•
•
•
50 to 60% of human body weight consists of water
Functions in body include:
o Carries nutrients and waste
o Maintains structure
o Participates in chemical reactions
o Acts as a solvent for nutrients
o Lubricates and cushions joints, spinal cord and fetus
o Helps regulate body temperature
o Maintains blood volume/pressure
Dehydration occurs when water output exceeds intake
o Signs = dry skin, dry mucous membranes, rapid heartbeat, low blood pressure,
weakness
Humans require 7 to 11 cups of water per day
Water sources:
o Water (100%)
o Fruits and Veggies (90-99%)
o Fruit juices (80-89%)
o Pasta, legumes, beef, and dairy (10-60%)
o Crackers and cereals (1-9%)
Biotin
•
•
•
•
•
Also known as vitamin H and coenzyme R
Found primarily in liver , kidney and muscle
Functions as an essential cofactor for 4 carboxylases that catalyze the incorporation of
cellular bicarbonate into the carbon backbone of organic compounds
Routinely provided to people receiving IV feeding and incorporated into almost all
nutritionally complete dietary supplements and infant formulas. In larger doses, can be
used to treat inborn errors of metabolism
Widely distributed in food stuffs, but small amounts relative to other vitamins.
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•
Deficiency is rare (unless having total IV feedings without added biotin, or the chronic
ingestion of raw egg whites -- Avidin in raw egg whites binds to biotin and doesn’t allow
body to absorb it)
Choline
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•
•
•
•
•
•
•
Dietary component of many foods
Part of major phospholipids (ie. phosphatidylcholine, also called lecithin) critical for
normal membrane function and structure
Major precursor of Betaine
Used by kidneys to maintain water balance and by liver as source of methyl-groups for
methionine formation
Precursor for neurotransmitter acetylcholine
In body, mostly found in phospholipids (ie. Lecithin and sphingomyelin)
Deficiency is healthy humans is rare
Choline and choline esters found in significant amounts in many foods consumed by
humans and some choline is added during processing (ie. infant formulas)
Phytochemicals
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•
Plant manufactured chemicals
Active derivatives extracted from leaves, stems, roots, flowers, and fruits or plants
classified into 3 main categories:
1. Toxic and no discernable therapeutic use.
ie. pyrrolizidine alkaloids, nicotine, hydrazine derivatives
2.
Toxic but useful for treatment of disease when used in controlled amounts
or for defined clinical conditions.
Ie. morphine, digitalis, vinca alkaloids
3.
Chemopreventative activity.
Ie. compounds useful against diseases such as atherosclerosis, cancer and
diverticular disease
•
•
•
•
•
Most active chemopreventative phytochemicals are high molecular-weight fibers such as
celluloids, pectins, lignins, and low-molecular weight compounds such as carotenoids,
flavanoids, isothiocyanates.
Majority of phytochemicals that have chemopreventative activity have no clearly defined
role as essential nutrients except for the vitamins (Ascorbate, tocopherols)
Deficiencies have not been identified, although low concentrations in diet are associated
with increased risks for cancer, cardiovascular disease (CVD) and diabetes
Data shows that best way to obtain these phytochemicals is through increased quantities
of fruits and veggies in diet
o All plants are sources of high-molecular weight fibres
Examples:
o Plants such as cabbage and broccoli = indoles, dithiolthionas,
isothiocyanates and chlorophyllins.
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o
o
o
Legumes such as soybeans, peanuts, beans = flavanoids, isoflavanoids,
and other polyphenols (antioxidants and estrogenic agonists/antagonists)
Citrus fruits and licorice root = mono- and tri-terpenes that act as
antioxidants, cholesterol synthesis inhibitors
Thioallyl derivatives such as garlic, leeks and onion = prevent thrombi
formation, decrease cholesterol synthesis and prevent DNA damage
Unit 4: Food Chemistry: Additives & Compositional Analysis
Chapter 14: Chemicals
-
FDA monitors use of additives (chemicals) and allows them to be used only if proven info. has shown
additive will accomplish intended effect
o Amt used cannot be more than needed to accomplish intended effect
Reasons for Use
- Food additive – any substance used intentionally in food and reasonably expected to (directly or
indirectly) become a component of food or affect characteristic of any food
o Any substance intended for use in producing, manufacturing, packaging, processing,
preparing, treating, transporting, or holding food
- The uses of food additives are governed by the Food, Drug and Cosmetic Act
- Intentional food additives include:
o Flavors
o Colors
o Vitamins
o Minerals
o Amino acids
o Antioxidants
o Antimicrobial agents
o Acidulants
o Gums
o Sequestrants
o Surface active agents
o Sweeteners
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-
-
The use of food additives is controlled by the Delaney clause
o Clauses states food industry cannot add any substance to food if it induces cancer when
ingested by man or animal, or if it is found to induce cancer by tests appropriate for the
evaluation of the safety of food additives
Additives are used to achieve one or a combination of four purposes:
1. To maintain or improve nutritional value
2. To maintain freshness
3. To aid in processing or preparation
4. To make food more appealing
Without additives or preservatives, some food would soon spoil or it would taste bland
o If some foods were not made storable, food would be wasted
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o If food note stored properly, can cause illnesses
o Some general categories of additives (chemicals) that benefit food: preservatives,
nutritional additives, colour modifiers, flavoring agents, texturing agents, aids to
processing
- Additives may have other functions including: hardening, drying, leavening, antifoaming, firming,
crisping, antisticking, whipping, creaming, clarifying, and sterilizing
o Without additives to help in the processing of food, grocery stores would be more limited
due to shelf-lives
o Tested and approved food additives are a part of today’s modern food technology
- Over past few years, food industry worked to reduce use of food additives w special emphasis on certain
groups (Ex: Artificial colours, preservative), driven by consumer desires
o Food companies spend millions to find out what consumers want and adjust their products
to meet demands
o Group of food additives that add the most value to foods are the flavors, generally used in
v low levels
o Sweeteners are the most heavily used additives
◙ Ex: Sucrose, high fructose corn syrup, dextrose, salt
o The per capita consumption of the others is less than 1lb per capita per year
- Over the years, chemicals have been added to food for unacceptable reasons, including:
o To disguise inferior products
o To deceive consumer
o To provide otherwise desirable results that lower the nutritional value
o To replace food manufacturing practices
o To use in amounts greater than necessary
Preservatives
- Preservatives include antioxidants, sequesterants, and anti-microbial agents
- Common antioxidants: BHA, BHT, TBHQ, erythrobic acid, sodium erythorbate, tocopherols, ascorbic
acid
- Common antimicrobial agents: benzoic acid, sodium benzoate, calcium propionate, potassium, sorbate
aka sorbic acid
- Sequestrants are chelating agents
o Organic compounds that rxt w metallic ions to bind in a relatively inactive structure
o Prevent metals from catalyzing rxns of fat oxidation, pigment discoloration, flavor loss,
and odor loss
o Common Ex: EDTA, citric acid and its salts, phosphoric acid and its salts
Nutritional Additives
- Vitamins and minerals are added to foods to make them more nutritious and sometimes to replace
nutrients lost during processing
o Ex: enriched bread, milk w vit. D added, margarine w vit. A and D added
Colour Modifiers
- Colours include both natural and synthetic colourants
- FD&C = Food, Drugs, and Cosmetics colours
o Thus, colourant can be used in all three of these products
o Marked D&C or C colourant = used in household products (Ex: shampoos)
- FDA responsible for controlling all color additives used in country
o All colour additives permitted for use in food are classified as either “certifiable” or
“exempt from certification”
- Certifiable colour additives permitted for direct addition to human food in US includes:
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o FD&C Blue No. 1 and 2, FD&C Green No. 3, FD&C Red No. 3 and 40, FD&C Yellow
No. 5 and 6, Orange B and Citrus Red No. 2 (restricted use)
- Colours exempt from certification include:
o Annatto extract, beta-carotene, beet powder, canthaxanthin, caramel color, carrot oil,
cochineal extract (carmine), cottonseed flour, ferrous gluconate, fruit juice, grape colour
extract, paprika, riboflavin, saffron, titanium dioxide, turmeric, vegetable juice
Certifiable colour additives are available for use in food as either dyes or lakes
o Dyes – dissolve in water; made as powders, granules (small hard pieces), liquids, or other
special-purpose forms
◙ Used in beverages, dry mixes, baked foods, confections, dairy products, pet foods,
etc.,
o Lakes – water-insoluble form of dye; more stable than dyes and ideal for coloring products
containing fats and oils or items lacking sufficient moisture to dissolve dyes
◙ Used in coated tablets, cake and donut mixes, hard candies
- Functions of colours are used in food products:
o To offset colour loss due to exposure of light, air, extreme temp., moisture, storage cdts
o To correct natural variations in colour. Off-colored foods often incorrectly associated w
poor quality. However, masking poor quality is an unacceptable use
◙ Ex: Some oranges often sprayed w Citrus Red No. 2 to correct green patches
o To strength colours that occur naturally but at levels weaker than those usu. associated w a
given food
o To provide a color identity to foods that would otherwise be colorless
◙ Ex: Red colors provide a pleasant identity to strawberry ice cream, and lime
sherbert is known by its bright green colour
o To provide a colourful appearance to certain “fun foods”
◙ Ex: candies and holiday treats for festive appearance
o To protect flavors and vitamins that may be affected by sunlight during storage
o To provide an appealing variety of healthy and nutritious foods that meet consumers’
demands
Flavoring Agents
- Some flavoring agents, such as spices and liquid derivations of onion, garlic, cloves, and peppermint,
enhance flavor
- Synthetic flavorings that resemble natural flavors have been developed and have the advantage of being
more stable than natural flavors
- Flavors cost the most and add the most value to products
Texturing Agents
- Emulsifiers are sometimes called surface active agents
o These improve the uniformity of a food
◙ Fineness of grain, smoothness and body of foods such as bakery goods, ice creams,
confectioneries
o Emulsifier Exs: Mono- and diglycerides, polysorbate 60 and 80, lecithin, and proteins
- Stabilizers and thickeners add smoothness, color uniformity, and flavor uniformity
o Used in foods: ice creams, chocolate milk, artificially sweetened beverages
o Ex: Pectin, vegetable gums, gelatins
Acidulants
- Acidulant – make food acid or sour
- Added to food primarily to change taste and control microbial growth
- Ex: citric acid, acetic acid, phosphoric acid, hydrochloric acid
Fat Replacers
- In attempt to reduce fat intake, food industry attempting to modify fat itself
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-
These approaches fall into following categories:
o Decreasing fat content
o Using fat replacers, substitutes, extenders, mimetics, or synthetic fat
- Fat replacers include various carbohydrate-based, protein-based, and fat-based replacers for diff’t food
categories
o Consumers constantly demand new and improved fat replacers
- Ex: Olean (sucrose polyester), Olestra, Amalean I and II (modified high-amylose corn), cellulose and
hemicelluloses, chitosan (fiber of crustaceans), hydrocolloids
Irradiation
- FDA considers irradiation of food as an additive
o Irradiated food is safe and will last longer
o Irradiation to control microorganisms on beef, lamb, and pork is safe and eventually could
mean that consumers will have less risk of becoming ill from contaminated meat
- Irradiation of fruits and vegetables means longer shelf life for those items
o Irradiation passes through food without leaving any residues
o Ionizing radiation kills bacteria and other pathogens in foods, but food never comes in
contact w radioactive materials; process does not make food radioactive
- Research on food irradiation dates back to 1920s
o US Army used process on fruits, veggies, dairy, and meat during WWII
o NADA routinely sends irradiated food on US spaceflights
o Shows any changes in irradiated food are similar to the effects of canning, cooking, or
freezing
o Nutritionally, irradiated food is virtually identical to nonirradiated food
Hazards
- Additives remain a public concern
o Majority of direct food additives are Generally Recognized as Safe (GRAS) substances,
meaning these ingredients may be added to food without extensive prior testing and were
established to avoid the burden of proving the safety of substances already regarded as
safe
o Banning of cyclamates produces a presidential directive to review the safety of the GRAS
substances and led to the FDA’s cyclic review of all direct and indirect additives
- A review of GRAS revealed ~90% present no significant hazard w normal human food uses
o Most remaining to be tested have not been associated w hazards to humans
o The other direct food additives have been approved, and uses regulated by FDA
o Indirect additives (Ex: used in production, processing, packaging, and that might migrate
to food) are numerous but normally occur in foods at trace levels, if at all
◙ Many may occur at parts per billion or less
o Examination of severity, incidence and onset of effects indicates that additives are the
lowest-ranking hazard
- Some chemicals are naturally a part of the food, but at such low levels they are harmless
Chapter 5: Food Composition
-
Food composition tables used to evaluate the nutritional value of food supplies, to develop food
distribution programs, to plan and evaluate food consumption surveys, to provide nutritional counselling,
and to estimate the nutritional content of individual diets
Determining the Composition of Foods
- Nutrition content of foods is influenced by variety, season, geographical differences, stage of harvesting,
handling, commercial processing, packaging, storage, display, home preparation, cooking, and serving
- Composition of foods determined by a variety of scientifically sound, standardized methods
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Proximate analysis – 1 system of approximating the value of a food or feed for nutritional purposes;
developed at the Weende Experiment Station in Germany more than 100 years ago
o This system separates a food into nutritive fractions through a series of chemical
determinations, which reflect a food’s nutritive value
o The different fractions included: water or dry matter, crude protein, ether extract or fat,
crude fiber, nitrogen free extract (sugars or starches), and ash or total mineral
- Newer methods of determining the composition of foods have replaced or supplemented the old
proximate analysis and allowed determination of more specific nutrients in foods
o Some of these newer methods include spectrophotometry, liquid chromatography, and
gas chromatography; allow the determination of fatty acids, cholesterol, amino acids,
specific minerals, and vitamins
Energy in Food
- Energy in the food is measured in terms of calories
- Calorie – a metric unit of heat measurement
o The small calorie (cal) is the amt of heat required to raise the temp. of 1g of water from
14.5 to 15.5
◙ Definition in US, and standard in thermochemistry: 1 cal = 4.1840 joules (J)
o A large calorie, or kilocalorie (Cal), usu. referred to as a calorie, sometimes as a kilogram
calorie, equals 1,000 cal
◙ Unit used to express the amt of nrg that a food provides when consumed
- Calorimeters measure the heat developed during the combustion of food
o Bomb calorimeters – used to determine the calorie content of foods
◙ Consists of an enclosure in which rxn takes place, surrounded by a liquid (Ex:
water) that absorbs the heat of the rxn and thus incr. in temp.
◙ Measurement of this temp. rise for a known weight of food permits the total amt of
heat generated to be calculated
o The food to be analyzed is placed inside a steel reaction vessel called a bomb
◙ The steel bomb is placed inside a bucket filled w water, which is kept at a cst temp.
relative to the entire calorimeter by use of a heater and a stirrer
◙ The temp. of the water is monitored w a thermometer fitted w a magnifying
eyepiece, which allows accurate readings to be taken
◙ Inserting an air space bt the bucket and an exterior insulating jacket minimizes heat
losses
◙ Slots at the top of the steel bomb allow ignition wires and an oxygen supply to
enter the vessel
◙ When an electric current passes through the ignition coil, a combustion rxn occurs
◙ The heat released from the sample is largely absorbed by the water, which results
in an incr. in temp.
- Many food composition tables are available, but the USDA maintains and updates data on the
composition of foods
-
st
Unit 5: Microbiology of foods
Chapter 13 pg. 199-207
Fermentations
· Fermentation is the oldest form of food preservation
· It is the breakdown of carbohydrate materials by bacteria and yeasts under anaerobic conditions.
· Produces acids and alcohols
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· Products produced by fermentation help preserve foods against microbial degradation
· Fermentation by lactic acid produces:
Ø Pickles
Ø Olives
Ø Some meat products (sausage and salami)
Ø Sour cream
Ø Cottage cheese
Ø Cheddar cheese
Ø Coffee
· Acetic acid produces cooking wine and cider.
· Lactic acid bacteria with propionic acid bacteria produces swiss cheese
· Molds produce blue cheese
· Yeasts are involved in the production of: beer, wine, rum, whiskey and bread
· Starter culture is a concentrated number of the organisms desired to start the fermentation
Benefits
· The main benefit is preservation of the product
· Adding flavor (in wine)
· Remove or alter existing flavors (in soya)
· Can alter chemical characteristics of food as in sugar to ethanol, ethanol to acetic acid, or sugar to
lactic acid
· Fermentation microorganisms produce vitamins and growth factors in the food
· Can enzymatically split polymers like cellulose into simple sugars that are digestible by humans
Control
· Can be controlled by:
Ø pH
Ø Salt content
Ø Temperature
· Acid or a low pH has an inhibitory effect
· Acid must be added or formed quickly to prevent spoilage or the growth of undesirable
microorganisms
· Microorganisms exhibit different tolerances for salt
· Many that cause spoilage cannot tolerate a slat concentration above 2.5 percent
· Salt in a solution is called brine
· When fermenting vegetables, salt draws water and sugar out
Uses of fermentation
Fermented dairy products
· The production of cheese relies on the fermentation of lactose by lactic acid bacteria
· Lactic acid bacteria also produces growth factors, which encourages the growth of nonstarter
organisms and provides enzymes that act on fats (lipases) and proteins (proteases) necessary for
flavor development during curing
· Yogurt basic ingredients: milk and a starter culture, the fermentation products of lactic acid,
acetaldehyde, acetic acid, and diacetyl contribute to the flavor.
· Buttermilk: the fermentation is allowed to proceed for 16 to 20 hours, to an acidity of 0.9 percent
lactic acid. Frequently used as an ingredient in the baking industry
· Acidophilus milk: traditional milk fermented with Lactobacillus acidophilus (LA), which has
been thought to have therapeutic benefits in the gastrointestinal tract
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· Sour cream: starter is similar to that used for cultured buttermilk. Inoculation and fermentation
conditions are also similar to those for cultured buttermilk, however fermentation is stopped at
an acidity of 0.6 percent.
Bread making
· Bread is leavened with yeast
· Bakers yeast is composted of the living cells of Saccharomyces cerevisiae
· Yeast performs its leavening function by fermenting carbohydrates such as the sugars, glucose,
fructose, maltose, and sucrose.
· Principal products of fermentation are carbon dioxide, and ethanol
· Some breadlike products like corn bread and certain kinds of muffins are leavened by chemicals
such as baking powder
Pickling
· Made by covering the fruit with a sweetened vinegar solution containing a spice or spices, such as
cloves, added for flavor
· Some vegetable pickles are produced by fermentation: the vegetable is placed in a covered crock
and allowed to ferment in a brine solution for a period of time ranging from a few days to several
weeks
· Vegetables, fruit, meat, eggs and nuts can be pickled
· Well known pickled foods: sauerkraut (cabbage fermented in brine), dill or sweet pickles made
from cucumbers, peach pickles, and pickled watermelon rind.
Processed meats
· Some have microbial starter cultures added to achieve fermentation to enhance preservation and
create a unique “tangy” flavor from the production of lactic acid
Vinegar
· An acidic liquid obtained from the fermentation of alcohol and used either as a condiment or as a
preservative
· Usually has an acetic acid content between 4 and 8 percent
· Flavor may be sharp, rich, or mellow depending on the original product used
· Made by combining sugary materials with vinegar or acetic acid bacteria and air
· The sugars or starches are converted to alcohol by yeasts, and the bacteria make enzymes that
cause oxidation of the alcohol to acetic acid
· There are several varieties: wine vinegars, tarragon vinegar has the distinctive flavor of the herb,
malt vinegar is known for its earthy quality, white vinegar, also called distilled vinegar; is made
from industrial alcohol; often used as a preservative or in mayonnaise because of its less
distinctive flavor and clear; untinted appearance. Rice vinegar is often used in Oriental countries
for marinades and salad dressings
Wine making
· In red wine making; grapes are crushed immediately after picking and the stems are generally
removed. The yeasts present on the skins come into contact with the grape sugars, and
fermentation begins naturally
· During fermentation, the sugars are converted by the yeasts to ethyl alcohol and carbon dioxide
· Glycerol and some of the esters, aldehydes, and acids that contribute to the character; bouquet
(aroma) and taste of the wine are by-products of fermentation
· Maturation of the wine may take years in 50-gallon oak casks
· The wine is then drawn off three or four times into fresh casks to avoid bacterial spoilage. Further
aging usually occurs after bottling.
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Brewing
· Brewing involves four steps: mashing, boiling, fermentation, and aging
1. Mashing: Infusion of malt, water, and crushed cereal grains at temperatures that
encourage the complete conversion of the cereal starch into sugars
2. Boiling. Concentration of the resulting “wort” (liquid) and the addition of hops.
3. Fermentation: addition of yeast to the wort, resulting in the production of alcohol and
carbon dioxide gas, by-products of the action of yeast on sugar.
4. Aging: proteins settle out of beer or are “digested” by enzymatic action. The aging
process may last from 2 to 24 weeks.
Chapter 8 pg 132-138
Principles of food preservation
· Food preservation involves the use of heat, cold, drying, acid (pH), sugar and salt, smoke,
atmosphere, chemicals, radiation, and mechanical methods
Heat
· Most bacteria are killed at 180 degree to 200 F, but spores are not. To ensure sterility requires wet
heat at 250 degree F for 15 minutes. High-acid foods require less heat.
Cold
· Microbial growth slows at temperatures under 50 degree F, but some psychrophiles will continue
slow growth.
Drying
· Drying reduces the water activity (Aw) in a food.
· Because microorganisms contain about 80% moisture, drying or dehydrating the food also
dehydrates the microorganism.
· Changing the amount of water in a food also alters the rate of enzyme activity and other chemical
reactions
Acid
· As the food becomes more acid (lower pH), the heat required for sterilization is reduced.
Sugar and salt
· Sugar, salt, and smoke are chemical means of controlling food deterioration.
· Addition of sugar or salt to a food item increases the affinity of the food for water, this removed
the water from the microorganism through osmosis
Smoke
· Smoke contains formaldehyde and other preservatives. The heat involved with adding the smoke
helps reduce the microbial populations, and it dries the food somewhat.
Atmosphere
· Changing the storage atmosphere reduces food deterioration
· The growth of aerobes is slowed by removing the oxygen; providing oxygen limits the growth of
anaerobes
· Adding carbon dioxide or nitrogen also slows deterioration
Chemicals
· Chemical additives such as sodium benzoate, sorbic acid, sodium or calcium propionate, and
sulphur dioxide retard the growth of microorganisms, modify enzyme activity, inhibit chemical
reactions, or modify the structure of foods
Radiation
· Includes X-rays, microwave, ultraviolet light, and gamma rays
· Radiation can destroy the microorganisms and inactivate enzymes
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Unit 6: Food Safety
Operations in Food Processing
Food processing is comprised as a series of physical processes:
1. Materials Handling
a.
Includes examples like harvesting on the farm/ranch, refrigerated trucking of perishable
produce, transportation of live animals
b.
Quality and sanitary conditions must be maintained during all these operations
c.
Losses and bacterial growth must be minimized
d.
Transfers and deliveries must be on time and that time kept to a minimum for efficiency
and quality
2. Cleaning
.
Foods grown or produced in open environments on the farm/ranch often requires cleaning
before use
a.
Cleaning ranges from removal of dirt to the removal of bacteria from a liquid food
b.
Brushes, high-velocity air, steam, water, vacuum, magnets, microfiltration, and
mechanical separation are all used to clean foods
c.
Food processing equipment also requires frequent, thorough, and special cleaning to
maintain quality of the product
d.
Floors and walls of processing facility must be cleaned as well
3. Separating
.
Achieved on the basis of density or size and shape
a.
Separations based on density differences include the separation of cream from milk,
recovery of solids from suspensions and removal of bacteria from fluids
i.Cream separator:
1. milk can be separated into skim milk and cream based on the
density difference between fat and nonfat solids of milk
2. A cream separator is used to obtain the cream from milk and is a
disc-type centrifuge in which the fluid is separated into low and
high density fluid streams,which permits the separate collection of
cream and skim milk
ii.Clarification:
1. Used to remove sediment and microorganisms
2. Clarifier is usually a disk-type centrifuge that applies force of 5000
to 10000 times gravity and forces the denser material to the outside
3. By periodically opening the bowl, the solids can be continuously
removed from the remainder of the fluids
iii.Membrane Processes
1. Reverse Osmosis (RO), ultrafiltration (UF), and microfiltration
(MF) are processes that use membrane with varying pore sizes to
separate based on the basis of shape and size
2. Reverse osmosis uses membranes with larger pores and will retain
proteins, lipids, and colloidal salts while allowing smaller
molecules to pass through the permeate phase
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3. Microfiltration, with pores less than 0.1, micron, is used to separate
fat from proteins and to reduce microorganisms from fluid food
systems
4. High pressure pumps required for RO and low-pressure pumps for
UF and MF
4.
Size Reduction
a.
Done using high-shear forces, graters, cutters or slicers
b.
Emulsions with very small fat globule droplets are frequently made with a homogenizer,
which is a high-shear positive pump that forces or reduce the size of an emulsion
c.
Typical equipment for size reduction in meat products and their component parts include:
grinder, bacon slicer, sausage stuffer, vertical chopper
5.
Fluid Flow(Pumping)
.
Achieved by gravity flow or through the use of pumps
a.
In gravity flow, the flow is laminar, where the flow is transferred from the fluid to the
wall between adjacent layers (adjacent layers do not mix)
b.
Two pumps commonly used for different purposes are centrifugal pump and positive
pump
6.
Mixing
.
Two major purposes of mixing are either heat transfer or ingredient incorporation
a.
Efficiency of mixer will depend on design of impeller, diameter of impeller, speed and
baffles
7.
Heat Transfer
.
Heat transferred or removed from a product
a.
Heating is used for destroying microorganisms to produce a healthful food, prolong shelf
life through the destruction of certain enzymes, and to promote a product with acceptable taste,
odor and appearance
b.
Five factors influencing the heat transfer into or out of the product are: heat exchanger
design, heat transfer properties (specific heat, thermal conductivity, latent heat), density, method
of heat transfer (conduction, radiation, convection), and viscosity
c.
Variety of heat exchanger used in food industry include plate heat exchanges, tubular
heat exchanges, swept surface heat exchangers
8.
Concentration
.
Achieved through evaporation and through reverse osmosis
9.
Drying
.
Three common methods are sun or tray drying, spray drying, and freeze drying
10.
Forming
.
To form foods into specific shapes
a.
Processes used are compacting, pressure extrusion, molds, powders and binding agents,
heat and pressure, and extrusion cooking
11.
Packaging
.
Used to improve the usefulness of the product, and protection from microbial
contamination, dirt, insects,light, moisture,drying, flavor changes, and physical alterations
12.
Controlling
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.
Tools used include valves, thermometers, scales, thermostats,and other instruments to
measure and control pressure, temperature, fluid flow, acidity, weight, viscosity, humidity, time
and specific gravity
Heat
•
Is the transfer of energy from one part of a substance to another by virtue of a difference
in temperature
Depending on the product and the use of the product, heat can be used to create varying degrees
of preservation including sterilization, commercial sterilization, pasteurization and blanching
• Sterilization
o Refers to the complete destruction of microorganisms
o Often requires at least 250 degrees F (121 C) for 15 min to destroy all spores
• Commercial Sterility
o Condition where all pathogenic and toxin-forming organisms have been
destroyed, as well as other organisms capable of growth and spoilage under
normal handling and storage conditions
• Pasteurization
o Low-energy thermal process with two main objectives:destroy all pathogenic
microorganisms that might grow in a specific product and extension of shelf life
by decreasing number of spoilage organisms present
o The product is not sterile and will be subject to spoilage
• Blanching
o Is a mild heat treatment, generally applied to fruits and vegetables to inactivate
enzymes that might decrease product quality
o May also destroy microorganisms and thus lead to increased product shelf life
o Primary objective is enzyme inactivation
Selecting Heat Treatments
• To pick the right heat treatment severity for a specific food, two factors must be first
determined: time temperature combination required to inactivate the most resistant
microbe and heat penetration characteristics of the food and the container
• Heat penetration characteristics of the food vary with the consistency and particle size,
heat penetration characteristics of the container vary with the size, shape and material
Cold
Unit 7: Food Processing: Part 1
Chapter 7 New edition: Page 112-124 Unit Operations in Food Processing
Food processing is the procedure of taking raw materials and preparing them so they become
foods for human consumption. Most food processing comprises a series of physical or chemical
processes that can be broken down into many basic operations. These unit operations can stand
alone but depend on logical physical principles. Unit operations include the following:
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Materials handling
o
Includes the range of operations such as harvesting, refrigerated trucking, transporting
animals, moving products from railcars to bakery storage bins, etc.
o
Sanitary and safety conditions must be maintained; bacterial growth must be minimized;
quality must be maintained; transfers must be on time
Cleaning
o
Cleaning ranges from removing dirt to removing bacteria from liquid foods; brushes, air,
steam, water, vacuum, magnets, microfiltration and mechanical separation are all used to clean
foods
o
Washing is the removal of soil, dust, organic matter, pathogens, including hands; steps
are wet, scrub, rinse, dry; includes sanitizing (reducing germs from surfaces) and disinfecting
(chemical products that destroy or inactivate germs)
o
SOPs (standard operating procedures) help to reduce spread of foodborne illnesses, keep
facilities clean, maintain records, reduce personal risk
Separating
o
Can be achieved based on density or size and shape
o
Cream Separator – milk can be separated into skim milk and cream
o
Clarification – sediment and microorganisms can be removed centrifugally in a clarifier
o
Membrane Processes – Reverse osmosis, ultrafiltration, microfiltration are processes that
use membranes with varying pore sizes to separate particles based on size and shape
o
o
Size reduction
Can be through the use of high-shear forces, graters, cutters or slicers
Homogenizers, grinders, bacon slicers, sausage stuffer, vertical chopper are all examples
o
Pumping (Fluid flow)
Transporting of fluids is achieved through gravity flow or the use of pumps
Mixing
o
An agitation (mixing) device may be placed in a tank to either provide heat transfer or to
incorporate ingredients
Heat transfer (Heat exchanging)
o
Heat is either transferred into a product (heating) or removed from it (cooling)
o
Heating is used to destroy microorganisms, produce a healthful food, prolong shelf life
by destructing some enzymes, and to promote a product with acceptable taste, odor and
appearance
o
Five factors influence heat transfer:
1. Heat-exchanger design
2. Heat-transfer properties of the product, such as specific heat (amount of heat required
to change the temperature without changing its state); thermal conductivity (rate by which hat is
transferred through a material); and latent heat (the heat required to change the state of a
material)
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3. Density (weight per unit volume)
4. Method of heat transfer, such as conduction; radiation; and convection
5. Viscosity, related to the amount of force required to move the fluid product
o
A variety of heat exchanges are used in the food industry, including pasteurization,
sterilization, drying, evaporation, refrigeration and freezing
Concentration
o
Can be achieved through both evaporation and reverse osmosis (RO)
o
Evaporation involves heating fluid in a vessel under a vacuum to cause water to change
from liquid to vapor;
o
Reverse osmosis, fluid passes through a semipermeable membrane with tiny pores that
permit only the transfer of water
Drying
o
3 common methods are 1) sun or tray drying, 2) spray drying, and 3) freeze-drying
o
1) sun or tray drying is good for fruits and vegetables, raisins are an example (dried
grapes)
o
2) products that are heat sensitive are freeze-dried, such as instant coffee; or fruits,
vegetables, meats and grains; moisture is removed without a phase change
o
3) spray drying is the most commonly used drying method; this is applied to fluid
products; different designs of spray nozzles are used to atomize the fluid into heated air
Forming
o
Processes used to form foods include compacting, pressure extrusion, molding,
powdering and binding agents, heat and pressure, and extrusion cooking (ie. pasta dough to form
shapes); examples are hamburger patties, cereal, butter, etc.
Packaging
o
Used for many reasons including shipping, dispensing and improving usefulness of the
product; also helps protect food from microbial contamination, dirt, insects, light, moisture,
drying, flavour changes and physical alterations; keeps food safe
o
Provides important information, marketing
o
Packages include metal cans, glass bottles, plastic bottles, paper, cardboard, plastic,
metallic films, etc.
Controlling
o
Food processors need to measure and control operations, this is usually done remotely
with automation and computers
Overlapping Operations
Most food processing includes a combination of unit operations to achieve the total
process
For example, the manufacturer of a dried coffee creamer from fluid and dry ingredients
includes mixing, fluid flow, size reduction, heat transfer, fluid flow, heat transfer, mass transfer,
pasteurization
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Conserving energy
Food processing is energy intensive, food processors are looking for new ways to
optimize use of energy
Other processes
New processes are being developed, such as ohmic heating, irradiation, super-critical
fluid extraction, and high hydrostatic pressure
ohmic heating: an advanced thermal-processing method, food material, that serves as an
electrical resistor, is heated by passing electricity through it
irradiation, controls spoilage and eliminates food-borne pathogens; uses the energy of
ionizing radiation
super-critical fluid (SCF) extraction, uses a gas such as carbon dioxide at high pressure to
extract or separate the food components; coffee and tea are decaffeinated using SCF extraction
high hydrostatic pressure (HHP), used to inactivate microorganisms; it subjects foods to
pressures between 40K-80K pounds per square inch for 5 minutes or less; high pressure does not
destroy the food, it inactivates microorganisms; popular in fish and shellfish industries; it is very
good but expensive
Chapter 9, pp 140-142 Heat
heating or cooking foods kills some microorganisms, destroys most enzymes, and
improves shelf life
heat is the transfer of energy from one part of a substance to another by virtue of a
difference in temperature
adding or removing heat to a substance raises or lowers its temperature, and expands or
contracts a substance, and alters its electrical resistance properties
Degrees of preservation
heat can be used to create varying degrees of preservation, including sterilization,
commercial sterility, pasteurization and blanching
Sterilization: the complete destruction of microorganisms; at least 121 degrees C for 15
minutes is needed to destroy all spores; it depends on the amount of food and can destroy the
quality of a food product; used for liquid or pureed foods
Commercial Sterility: all pathogenic and toxin-forming organisms have been destroyed
Pasteurization: low energy thermal process to destroy pathogenic microorganisms and to
extend shelf life by decreasing the number of spoilage organisms; milk and eggs are pasteurized
to kill microbes
Blanching: a mild heat treatment generally applied to fruits and vegetbles to inactivate
enzymes that might decrease product quality; also loosens the skins of some fruits and
vegetables, making them easier to peel
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Selecting Heat Treatments
Two factors to consider: 1. The right time and temperature combination to inactivate the
most resistant microbe; 2. The heat-penetration characteristics of the food and container
Heat Resistance of Microorganisms
Most resistant microbe in canned foods is Clostridium botulinum (botulism), so food
processors must use a time-temperature combination to kill this deadly microbe
Heat kills bacteria logarithmically; if 90% are killed in first minute, then 90% of those
remaining alive will die the second minute, etc.
Chapter 10, pp 153-158 Cold
Cold (cool) storage, refrigeration and frozen storage are methods of food preservation
and processing that differ in temperature and time
Cool storage is any temp from 16 to -2 degrees Celsius
Refrigerator temperatures range from 4.5 to 7 degrees Celsius
Frozen storage temperatures are from 0 to -18 degrees Celsius
Microbes grow more rapidly at temperatures above 10 degrees Celsius, however some
growth occurs at sub-freezing temperatures if water is available; little growth occurs below -9.5
degrees Celsius
Refrigeration and cool storage
Cool storage is the gentlest of all food-preservation methods, it affects taste, texture,
nutritive value and color the least, but is only a short-term preservation method
Refrigeration is also a gentle method and extends shelf life by a few days or a week; it
slows down but does not stop spoilage of food; some microorganisms called psychrophilics will
grow at refrigeration temperatures
Requirements of refrigerated storage
Low temperatures, air circulation, humidity control and modified gas atmosphere are
required
Requirements are affected by insulation, frequency of door opening, and quantity of hot
product added daily
Freezing and frozen storage
Freezing point of food is below 0 degrees Celsius
Freezing will not destroy microorgnisms or inactivate enzymes, but will slow their
deteriorative effect
Freezing causes minimal changes in the quality of food in size, shape, texture, color,
flavour and microbial load
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Chemical changes during freezing
Enzymes in fruits and vegetables are slowed down and can cause color and flavour
changes, as well as loss of nutrients
Enzymes in vegetables: Blanching, or exposing a vegetable to boiling water or steam
briefly, inactivates enzymes in vegetables; the vegetable must then be rapidly cooled in ice water
to prevent further cooking
Enzymes in fruits: can cause browning and loss of vitamin C; they are not usually
blanched. Instead, the use of chemical compounds controls enzymes in frozen fruits. Ascorbic
acid (vitamin C) is commonly used in pure form or commercial mixtures.
Rancidity in foods: another chemical change in frozen products is the development of
rancid off flavours; occurs when fat is exposed to air over a period of time; removing air from
the freezer container helps control this.
Textural changes during freezing
Freezing consists of freezing the water in the food, then it expands and the ice crystals
cause the cell walls to rupture; the texture of the product is then softer after it thaws; cooking
also softens cell walls so changes are less noticeable on cooked foods.
Rate of freezing: freezing products as quickly as possible can control cell wall rupture
Changes caused by fluctuating temperatures: fluctuation can cause ice to thaw and
refreeze, further damaging cells and creating a mushier product
Moisture loss: moisture loss, or ice crystals evaporating from the surface area of a
product, produces freezer burn, a grainy, brownish spot where the tissues become dry and tough
Microbial growth in the freezer
Freezing does not destroy microorganisms, sufficient numbers remain to multiply and
cause spoilage when the product thaws
Freezing methods
Include the still-air sharp freezer, blast freezer, and fluidized-bed freezer; in immersion
freezing, intimate contact occurs between the food or package and the refrigerant
Packaging
Protects against dehydration, light and air; must be strong, flexible and liquid tight
Chapter 11, pp 164-169 Drying and Dehydration
-
Drying and dehydration both remove water from foods
Dehydration
water is removed from foods under natural conditions in the field with grains, raisins and
seeds
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dehydration is the almost complete removal of water, commonly used in dried milk,
coffee, soups and corn flakes
it results in decreased weight, increased amount of product per container, and decreased
shipping costs
the purpose is to remove enough moisture to prevent microbial growth
4 factors affect heat and liquid transfer in food products during drying:
1. Surface area - the greater surface area, the faster a product dries
2. Temperature – the greater the temperature differences between a product and the drying
medium, the greater the rate of drying
3. Humidity – the higher the humidity, the slower the drying
4. Atmospheric pressure – the lower the pressure, the lower the temperature required to remove
water
- dehydration can be enhanced by changing these factors.
Drying Curve
When foods are dehydrated they lose water at a changing rate; rapidly at first, then slower
toward the end of the drying period
Solute Concentration
Foods high in sugar or other solutes dry more slowly
Binding of Water
As a product dries, its free water is removed; this is the easiest to remove water and it
evaporates first
Chemical Changes
Several chemical changes can occur during drying:
1.
Caramelization: of sugars occurs if the temperature is too high; sugars on the surface of
the food start to brown during cooking
2.
Enzymatic browning – is caused by enzymes and can be prevented by inactivating the
enzymes before drying, as in by pasteurizing or blanching the food first
3.
Nonenzymatic browning – or Maillard browning, is controlled by dehydrating the food
rapidly through the moisture ranges that are optimal for Maillard browning
4.
Loss of ease of rehydration – rehydrated dried products have an altered texture
5.
Loss of flavour – preventing a loss of flavour during dehydration is almost impossible
Drying Methods
Common drying methods are:
1.
Air Convection – has an insulated enclosure, a way of circulating air through the
enclosure, and a way to heat this air; examples are kiln, tunnel, air lift, spray, cabinet, tray or pan
2.
Drum – drum or roller driers are used to dry liquid foods, purees, pastas, and mashes;
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they are applied in a thin layer onto the surface of a revolving heated drum; examples are milk,
potato mash, tomato paste, and animal feeds.
3.
Vacuum – produces the highest quality of product but is most costly; includes a vacuum
chamber, heat source, device for maintaining a vacuum, and a component to collect water
vapour; examples are fruit juices, instant tea, milk, and delicate liquid foods
4.
Freeze-Drying – used to dehydrate sensitive, high-value foods like coffee, juices,
strawberries, whole shrimp, diced chicken, mushrooms, steaks and chops; protects the delicate
flavours, colours, textures, and appearance of foods. Food is frozen first and then under
conditions of low vapour pressure (a vacuum) water evaporates from ice without the ice melting.
Unit 8: Food Packaging
Why are foods packaged?
• Containment
o Design of packaging equipment and units helps divide the product into individual
units (cartons, cans, pouches) which can further be grouped together (six-pack)
• Protection
o Important to maintain the integrity of the product to keep desirable characteristics
in and undesirable elements out.
• Convenience
o Light weight, easy to open and hold, suitable serving size, easy for pouring,
reheating, and resealing
• Communication
o Messages regarding identity, quantity, and ingredient content of the product
o Usage and storage instructions
o Price
o Nutritional value
o Promotional information
o Attractive to eye of customer
Types of packaging materials:
• Metal
o Tin, aluminum, foil
o Disadvantage - not suitable for microwaves, corrosion. Fixed by adding coating to
insides of cans
• Glass
o Advantages - transparent, chemically inert
o Disadvantage - easily breaks, heavy weight = higher transport costs
• Paper and fiberboard
o Outer wrappings, boxes, and bags
o If used as primary container, it must only have coatings that are food grade (nontoxic non-reactive)
• Plastics
o Polymers of repeating organic molecules that can be made into flexible films or
semi-rigid trays/containers.
o Disadvantages - gas permeability, migration of plastic components into food, and
temperature exposure limits
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Plastics can tolerate high temperatures
Environmental impact of food processing and consumption
• Environmental impact of food packaging disposal
o Over packaging of food products contributes to landfills
o National Packaging Protocal (NaPP) (1989)
▪ promotes waste reduction through source reduction (use less stuff in the
first place), reuse, and recycling programs
▪ Improve management strategies to reduce disposal of packaging waste in
environment/incineration
▪ Goal: reduce amount of packaging waste to 50% of 1988 levels by end of
2000
▪ Surpassed by mid 1990s
o Food packaging impact on environment depends on many complex scientific,
social, and ethical issues
o Ex: do we replace plastic milk pouches with glass bottles? They are reusable but
weigh much more so transport costs are much more, and must be cleaned, so is it
really worth it?
o Consider balance between environmental responsibility, packaging utility, and
consumer concerns
• Environment impacts of food processing
o Consumer concerns have motivated companies to re-evaluate their approaches to
waste management
o Economic factors are strong driving forces
▪ Some municipalities give fines to sewage treatment plants if certain levels
of organic matter are too high
▪ To avoid these fines, alternative means of pre-treating waste must be
found or try to recover usable components from waste products that can be
marketed
o
Unit 9: Food Engineering and Physics
Unit 10: Toxicology and Biotechnology
Safety, Hazards and Risks - 1st Edition: Chapter 25 p.452
• Food safety includes: microbiological, chemical, and foreign material that could cause injury
or harm.
1. Illness is often transmitted through disease germs, via objects such as shared cups and
cutleries, as well as coughing and sneezing. Food can also serve as transmitter, which can
sometimes transmit animal pathogen to humans.
2. Food poisoning and food infections are often caused by bacteria
• Refers to gastroenteritis (stomach and intestinal tract illness) after consuming the
bacteria containing food.
• Some pathogens release toxin, which is the source of illness
• Other pathogens only becomes active inside the digestive system, which then
causes the infection.
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3.
Other microorganisms can also cause food poisoning.
• Food either contains chemical toxins or poisonous substance from plant or animal.
• Example 1: tuna containing mercury.
• Example 2: apple containing alar (chemical plant growth regulator).
Unit 11: Sensory Attributes
Unit 12: Product Development
Chapter 16
Concentrated and Dried Dairy Products
fluid milk contains approx. 88% water
concentrated and dried dairy products go through water removal
o increases shelf life, convenience, product flexibility, decreased transportation
costs, and storage
evaporated skim or whole milk
o milk is concentrated at low temperatures by vacuum evaporation
o the ability of milk to withstand intensive heat treatment depends on its salt balance
o extended shelf life by being canned and sterilized
sweetened condensed milk
o extended shelf life due to addition of sugar
- sucrose increases the osmotic pressure preventing the growth of
microorganisms
condensed buttermilk
o can be evaporated or mixed with skim milk
- may oxidize due to high fat content
milk powder
o heat treatment destroys microorganisms and inactivates the enzyme lipase that
could cause lipolysis during storage
whey powder
o reverse osmosis can be used to partially concentrate the whey prior to vacuum
evaporation
whey protein concentrates
o commonly processed using ultrafiltration, although reverse osmosis,
microfiltration, and demineralization methods can be used
o drying is done at lower temperatures to reduce protein denaturation
Yogurt
starter culture in north America is a blend of Streptococcus salivarius thermophiles (ST) and
Lactobacillus delbrueckii bulgaricus (LB)
ST grows faster and produces both acid and carbon dioxide
Microorganisms are responsible for the texture and flavour
ST initially drop the pH to 5.0 and LB furthers it to 4.0
Flavour comes from fermentation products: lactic acid, acetylaldehyde, acetic acid, and diacetyl
Milk substitutes
most common substitute for milk is margarine
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other substitutes include frozen desserts, coffee whiteners, whipped toppings, and imitations
milk soy milk)
they are made by combining non dairy fats or oils with certain classes of milk components
Reduced fat products
fat is replaced in a milk product must perform the same functions (ie mouthfeel)
fat substitutes are made of proteins and carbs that bind large amounts of water
new reduced fat products are non absorbable or digestible (ex olestra)
Chapter 17
Meat
Meat specialities
dry sausages are fermented in order to encourage lactic acid bacteria growth which acts as a
preservative and adds tangy flavour
summer sausage is the general classification for semi dried sausage
Freezing
if the cut of meat is fatty like pork, if it is properly wrapped it can be frozen for months
o limited because the fat oxidizes in freezers causing an off taste
beef can be held for years
few cured meats and sausages are frozen because the salt causes rancid flavours
flavours of the spices in sausage may also change during freezing
Cooking
dry heat raises the temperature very quickly so it is good for cuts of meat that are low in
connective tissue (ex steak)
low and slow temperatures are recommended for cuts of meat with high connective tissue
o application of moist heat turns tough collagen into tender gelatin
trichinosis is destroyed at 58 degrees Celsius, anything more will cause dehydration of the meat
repeated warming and chilling of precooked products could lead to contamination and
incubation of pathogens
Contract acceptance certification
ensures integrity and quality of poultry
USDA certifies on:
o Kind of class
o Type and style
o Formula, processing, and fabrication
o Lab analysis
o Net weight
o Labeling and marketing, package and packaging
o Storage and transportation
Eggs
Storage
can be stored at -1 dC for up to six months in the shell
can be frozen in or out of the shell
after removing the shell they can be dehydrated
salmonella has been found recently inside eggs (was once thought to be sterile)
o salmonella has only been found in a small number (2-3/10,000)
o are considered potentially hazardous but should be fine if they are refrigerated
Fertile eggs
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fertile eggs are not more nutritious than non fertile
they are also more expensive to produce
Organic eggs
organic eggs are from hens that are fed rations that have ingredients that were grown without
pesticides, fungicides, herbicides, or commercial fertilizers
no commercial production feed ever contains hormones
higher production costs + lower volume = more expensive egg
nutrition content of eggs is not affected by whether or not the ration is organic
Egg substitutes
level of cholesterol in eggs has slowed consumer consumption
reduction of cholesterol has included separating the cholesterol from the yolk and to
formulating new products and combining them with the albumen
have also looked into changing the genetics of the chicken so they produce less fat in the eggs
Chapter 18
Shellfish
may be marketed in the shell or shucked (removed from the shell), headless, and as cooked
meat
Fish by products
parts that aren’t eaten by humans are ground up to produce fish meal which is used in animal
feed or as fertilizer
fish protein concentrate (FPC) is produced from the dehydrated and defatted fish
roe is the mass of eggs and sacs of connective tissue enclosing the thousands of eggs
Storage
need to be refrigerated
should be cooked within two days of purchase
fish shouldn’t sit I its own juices for long because the flesh deteriorates more quickly
frozen fish should be thawed in the fridge, thawing at temperatures over 4.4 dC causes
excessive drip loss and adversely affects taste, texture, aroma, and appearance
New products
minced fish flesh is washed to remove pigments and flavors
leaves an odorless, flavorless, high protein product called surimi
o can be shaped into other products such as crabmeat and lobster
Chapter 19
Corn refining
corn refining is today’s leading example of value added agriculture
inspection and cleaning
o corn is cleaned twice before steeping
syrup conversion
o starch is liquefied in the presence of acid and/or enzymes that convert the starch to
a low dextrose solution
o the sooner the conversion from starch to sugar happens, the sweeter the syrup will
be
fermentation
o dextrose is one of the most fermentable of all the sugars
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o following syrup conversion refiners pipe dextrose to fermentation facilities where
the dextrose is converted to alcohol by traditional yeast fermentation or to amino
acids and other bioproducts through either yeast or bacterial fermentation
o the broth is distilled to recover alcohol
Bioproducts
the most recognizable bioproduct from corn is ethanol – a motor fuel additive
fermentation can create organic acids, amino acids, vitamins, and food gums
citric acid and lactic acid from corn can provide tartness, control pH, and are feedstocks for
further products
amino acids from corn are used in animal feeds as they usually do not have enough lysine in
them
Breakfast cereals
cereal grains vary in composition depending on the type of grain, the part of the grain used, the
method of milling, and the method of preparation
the carb may be changed by the use of malt or may be browned (dextrinized) by dry heat
disodium phosphate can be added for quick cooking, it changes the pH of the cereal and causes
it to swell faster and cook in a shorter time
Chapter 20
Fruit juices
orange juice is the most commonly processed juice
the main steps of production of most juices include:
o extraction
o clarification
o deaeration
o pasteurization
o concentration
o essence add-back (flavors)
o canning or bottling
o freezing
pear juice is a base for many juices because its fruit flavour is strong but not characteristic
juices that are low in vitamin C are usually fortified with the vitamin
Processing of vegetables
vegetables for canning and freezing are grown specifically for that purpose and the processing
preserves a lot of their nutritional value
their canning is similar to that of fruits
once sealed canned vegetables, the containers are cooked to assure the product will keep
without refrigeration
frozen vegetables are slightly precooked which ensures that they will retain much of their
natural appearance and flavor for long periods of time in storage
without blanching, frozen vegetables would prematurely turn brown or oxidize before marketed
the byproducts of fruits and vegetables often become feed for livestock
o ex citrus pulp and processed potato wastes can be fed to cattle
Chapter 21
Products made from fats and oils
the largest portion of the market for edible oil products is that which includes margarine,
spreads, dressings, retail bottled oils, and frying oils
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the source of the lipids have allowed for a healthier product
stability and the functionality are obtained by their modification through hydrogenation
monoglycerides and diglycerides are used as emulsifiers in a variety of foods
Fat substitutes
approaches to fat reduction falls into one of two categories: decreasing fat content, or using fat
replacers, substitutes, extenders, mimetics, or synthetic fat
proteins can be used in some foods to give a similar mouthfeel to fat
carbs can be used to increase the viscosity and mimic oil
sugar esters are the newest form of fat substitutes as they are chemically similar but are not
absorbed or metabolized in the body
chemical tests can determine the degree of unsaturation of the fatty acids in a fat, this is
expressed as the iodine value
o the higher the iodine value the greater degree of unsaturation
another chemical test yields the peroxide value which indicates the degree of oxidation that has
taken place in a fat or oil
hydrolytic rancidity refers to the rancidity that occurs under conditions of moisture, high
temperature, and natural lipolytic enzymes
Chapter 22
Confectionary manufacturing processes
the enrober is used to create assorted chocolates, it covers centers (ex nuts) with chocolate
strict tests are performed for the viscosity of chocolate, the cocoa butter content, for acidity, for
the fineness of a product, and for the purity and taste of the desired finished product
must follow rules according to the FDA
Sugar substitutes
sugar alcohols are made by chemically reducing a sugar to an alcohol
since they are not fermentable by bacteria in the mouth, they do not contribute to tooth decay
sugar alcohols are less sweet and are often found it products that are labeled “sugar free”
although this doesn’t mean that they are calorie free
high intensity sweeteners are used to reduce the caloric content, this is because less of the
sweetener is required or the sweetener is not metabolized by the body
high intensity sweeteners do not usually provide the same functionality as sugar so additional
additives are used to provide bulking, mouthfeel, and other characteristics
Chapter 23
Carbonated non alcoholic beverages
carbonated soft drinks are the most popular beverage
the most highly used sugar in soft drinks is high fructose corn syrup (it used to be sugar)
because they are sweeter
nonnutritive sweeteners that have been used in soft drinks include saccharin and cyclamate,
but currently reduced calorie soft drinks use aspartame
carboxymethyl cellulose or a pectin are sometimes added to the drink for mouthfeel
flavors used in soft drinks include synthetic flavors, natural flavor extracts, and fruit juice
concentrates
heated sugar produces a caramel colour which is used in darker beverages
if natural fruit juices are used synthetic colours are often added
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carbon dioxide in soft drinks adds to the acidity but the main acids used are phosphoric, citric,
fumaric, tartaric, and malic acids
o they also lower the pH
water is the major ingredient in soft drinks
the water needs to be pure because any impurities can react with the other chemicals in the
drink
Noncarbonated herbal and healthful beverages
the world’s first vitamin-fortified fruit drinks appeared in 1948
Hi-C is the world’s largest brand of vitamin fortified fruit drink
Gatorade was produced to help with dehydration
Other vitamin fortified drinks include sobe and Snapple
Alcoholic beverages
fermentation of a carb source such as corn, rye, rice, molasses, agave, wheat, potatoes, and
barley creates alcoholic beverages such as beer, whiskey, sake, vodka, rum, and tequila
fermentation of sugar containing juice such as grape juice or other fruit juices creates wines or
brandy
Beer
beer and ale are produced from malt, hops, yeast, and water
malting is when the barley grains are soaked (steeped), germinated, and then dried
the malt serves as a source of amylases that will break down the starch into sugar for the yeast
to ferment
mashing involves mixing the ground malt with a previously boiled malt adjunct
the enzymes in the malt digest the starch in the adjunct and release the sugar
the mix is heated to denature the enzymes and then filtered leaving a filtrate known as wort
boiling is when hops are added to the wort and boiled which serves to:
o concentrate the solids
o kill microorganisms
o inactivate enzymes
o coagulate proteins
o caramelize the sugars
fermentation is when wort is inoculated with a beer yeast
completion occurs after the beer has aged from several weeks to several months; this storage
time is known as lagering
cold pasteurization or filtration removes leftover yeast and bacteria
Wine
wines fall under three categories: natural/table wines, sparkling wines, and fortified wines
vinification is the production of wine from grapes
sparkling wines are made by the champagne method in which cultured yeasts and sugar are
added to the base wine inducing a second fermentation in the bottle
the alcohol content of fortified wines is due to the addition of alcohol
Nonalcoholic beverages
Coffee
coffee beans or cherries come from trees
the dry and wet methods of preparation produce distinctive flavors in the beans
removal of pulpy berry from skin is achieved by bacteria that break down pectin
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this is followed by an acid fermentation by lactic acid bacteria
after fermentation beans are dried, hulled, and roasted
Herbal tea
herb tea is made from many plants using not only just leaves but flowers, roots, bark, and seeds
most herb teas contain no caffeine
leaves are dried by spreading them on large teas or hanging them upside down in bundles
this must be done quickly to retain the plants natural oils and color
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Food Science: FOOD 2010 Final Exam Unit and Chapter
Summaries
Unit 1: Introduction to Food Science and the Food Industry
What is food science and technology?
Food science: is an APPL)ED science, which takes principles from the basic sciences bio,
chem, phys, math and applies them to the study of nature of foods, and to solve food‐
related problems
Food technology: is concerned with the development, processing, preservation, packaging,
and distribution of safe, nutritious, and appealing food.
Food science has become an interdisciplinary mix, which includes influence of the social
sciences, agriculture, business, and the health sciences.
Nutrition, dietetics and culinary arts are closely associated but these disciplines focus on
different aspects of food
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Major disciplines in food sciences are:
Food chemistry: examines the chemical composition and physical properties of foods
Functional properties of proteins, carbs, lipids, water, vitamins, minerals, flavours, colours,
enzymes
Chemistry of reactions occurring prior to and during processing
Chemistry of reactions occurring during spoilage
Qualitative and quantitative analysis of food composition food analysis
Physical behaviour of food
Food toxicology
Food microbiology: examines role of microorganisms in foods
Food spoilage
Food fermentation
Prevention of food‐borne illness due to pathogenic microorganisms
Food Processing: is concerned with techniques for preparing and packaging food to ensure
safety, wholesomeness, product consistency, and nutritional quality
Preservation of quality during and after harvest of raw materials
Methods for food preservation
Product differentiation e.g. making bread from water, flour, and yeast
Process control and automation
Food packaging
Waste management
Food facility sanitation
Quality control
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Food engineering: is concerned with applying physical and engineering principles to
control unit operations in food processing
Mass transfer
(eat transfer and thermodynamics
Fluid flow dynamics
Mechanics
Process control and automation
major disciplines‐ all interrelated
study of food market factors‐ recently considered a field. This field provides vital
information to ensure marketability of food products.
Sensory evaluation
Communications
Food industry trends
Food laws and regulations
Consumer behaviour
Careers in Food Science
Examples of careers in food science: Waste management, food marketing, biotechnology,
food processing, nutrition, sensory science, packaging, toxicology, food microbiology, food
law, quality assurance, sanitation, food engineering, consumer relations, food chemistry,
food service, food safety, food analysis
Who are the stakeholders in the food industry?
Stakeholder‐ is one who holds an interest in some thing
Chain of production: the concept has evolved out of the philosophy that food production
involves a series of integrated steps originating from production of raw agricultural
commodities to consumption of finished products in a home Farm to for Fork
Groups of stakeholders in the chain of production:
Producers  Processors Distributions Retail Consumers
OR Food Service Consumers
Producers‐ farmers, harvesters
Processing‐ food manufacturing, suppliers
Distributors‐ wholesale, imports/exports
Retail‐ Supermarkets, specialty stores
Food Service‐ Restaurants, )nstitutions
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What roles does stakeholders play in the food industry?
As consumers, our roles involve purchasing and using products and we can influence in
shaping trends in the industry by the types of products and services we buy or demand
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Consumers can influence corporate ethics example: rejection of animal testing
Producers and processors are primarily concerned with production aspects
All sectors of the production chain up to the consumer are involved in marketing and selling
their products
The processing sector is concerned with producing value‐added products to sell as
ingredient for other processors, or as finished products destined for the retail or food
service markets. Sale of products is often mediated by distributors.
Trade and consumer associations act as advocates for interests of particular sectors
What is the economic and social impact of the agri‐food industry?
)n many countries, the agricultural and food industries are large contributors to the gross
domestic product, national tax revenues, and employment.
Many industries not just food industries have looked towards foreign markets for sales
and procurement of products and services in a trend commonly referred to as globalization
Example of a global trading block is: North American Free Trade Agreement NAFTA ‐
Canada, United States and Mexico
Global Food )ssues:
Various food scientists from academic, government, and industry have devoted part or all of
their careers to assisting foreign countries in matters related to prevention of food‐borne
illness, sustainable agricultural practices, marketing of commodities, food security, and
prevention of malnutrition.
Food security: assured access to enough food at all times for an active and healthy life.
Food insecurity: occurs whenever the availability of nutritionally adequate and safe food or
the ability of acquire acceptable foods in socially acceptable ways, is limited or uncertain
Hunger: uneasy or painful sensation caused by recurrent or involuntary lack of food and is a
potential, although not necessary consequence of food insecurity. Over time, hunger may
result in malnutrition.
Chapter Two pg
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Food composition: refers to the substances or component found in a beverage or food
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Key Nutrients that compose foods:
larger molecules: protein, fat lipid , and carbohydrates starch, sugars, and fibre
smaller molecules: water, vitamins, minerals, and phytochemicals
Beverage‐ a drinkable liquid, consumed for a variety of reasons including
thirst quenching
stimulant effect
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alcoholic content
health value
enjoyment
Nutrients‐ substances in food and beverages that when absorbed in the body are used for
specific functions like growth, maintenance, and repair of tissues
Degree of Brix of Beverages: measurement of sucrose concentration in a beverage, it is
equal to the weight percent of sucrose in a solution grams of sucrose per
grams of
sample
‐beverages naturally sweetened or have sweeteners added during processing
‐commonly used sweeteners are sugars sucrose and high fructose corn syrup
‐sucrose is a special carbohydrate molecule called disaccharide, composed of two small
sugar molecules bonded together
‐fructose is a sweeter sugar than sucrose or glucose and will increase the sweetness in a
beverage sucrose inversion
‐factors that promote sucrose inversion are low storage p( high acidity and high storage
temperatures
Cereals, Grains, and Baked Products
‐among the World s major crops
‐inculde cereal grains, corn, rice, wheat, barely, millet, rye, sorghum, and oats
‐cereal grains are high in carbohydrate content, such as starch and the sugar glucose,
maltose, fructose, as well as fibre
Leavening‐ expansion of bread dough. (igh volume with open aerated crumb texture
Biological Value (BV): amount of nitrogen derived from food protein that is used in the
body to promote growth
‐BV is related to the amino acid content of a protein
‐for comparative purpose the hen s egg is used as a standard reference of a high quality
protein
Bioavailability: degree to which nutrients are digested and absorbed in the body. )t is
influenced by food source animal vs. plant and food processing ex. Vitamin B is destroyed
by heat
Fruits and Vegetables
Fruit: a fleshy or pulpy plant part commonly eaten as a dessert to to its sweetness
Vegetable: a plant or plant part that is served either raw or cooked as part of the main
course of a meal
Botanical terms:
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Fruit: ripened ovary of a plant, which means that it contains the seeds
Vegetable: herbaceous plant containing an edible port such as a leaf, shoot, root, tuber,
flower, or stem
*Odd fruits: tomatoes, squash, and avocadoes
‐most fresh fruit and vegetables, though there are exceptions are high in water content up
to % , low in protein up to . % and low in fat up to . %
‐contains various minerals and are a good source of both digestible carbohydrates sugars
and starches and indigestible carbohydrates fibre‐including cellulose and pectin
substances
‐good source of specific vitamins: vitamin A precursor, beta carotene green leafy vegetables
and yellow‐orange fruit and vegetables and vitamin C
(ealth Benefits:
‐recommend daily serving of ‐ fruit and ‐ vegetables
‐protective against heart disease and certain cancers
Ripeness‐ peak condition of flavour, colour, and texture for a particular fruit
Maturity‐ the condition of a fruit when it is picked
Harvesting‐ collection of fruits and vegetables at the specific time of peak availability in
terms of colour, texture, and flavour in order to market them
Senescence‐ decline in the quality of stored, respiring fruits and vegetables that occur after
harvesting
Dehydration‐ moves moisture from fruit to prevent microbial and enzymatic deterioration
Legumes‐ edible seeds and pods as beans and peas of certain flowering plants include
beats, lentils, soybeans, and peas
‐most legumes offer good quality protein compared to other plans and are low in fat
Isoflavones‐ class of phytochemicals found in soyfoods that may be effective in
prevention and treatment of cancer and certain chronic diseases
Meat
‐source of high quality protein and is valued for its cooked flavour and tender texture
‐red meat flesh of cattle, pigs, sheep
‐white meat poultry chicken, turkey, duck
‐provides various B vitamins, iron, magnesium, and other minerals
Collagen‐ white connective tissue. Toughness in meat is directly related to the amount of
collagen it contains. Older animals tend to have high levels of collagen and yield tougher
meat than younger animals
Seafood
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‐more than just fish, includes calms, oysters, lobsters, scallops, and other food animals
derived from oceans, lakes, and streams
‐ division of fish: finfish and shellfish
‐finfinish: fish with backbone and fins
‐shellfish: crustaceans which are sea invertebrates with a harder upper shell and with a soft
under shell examples: calms, oysters, scallops
‐protein in fish highly digestible and good source of all amino acids
‐fish fat is rich in unsaturated fatty acids as well as fat‐soluble vitamins A and D
‐B vitamins found in fish muscle and can be rich in sources of iodine, some magnesium,
calcium, and iron
Why are Fish so Perishable?
‐more than any other kind of animal flesh
‐ reasons: fish microbiology, fish physiology, and fish fat chemistry
Eggs
‐white contains water and protein
‐yellow yolk contains % calories of eggs, fatty portion of the egg, also has protein, iron,
other minerals and vitamins
Milk and Dairy Products
‐whole cow s milk is typically % water, . % protein, . % fat, . % carbs, . % ash
‐milk fat contains not only cholesterol and phospholipids but also fat soluble vitamins A,D,E,
and K and yellow carotenoid pigments
‐primary milk carbohydrate is lactose milk sugar
‐many adults have diffculty digesting milk products because they do not produce enough of
the enzyme lactase that digest lactose
Milk Proteins: Casein and Whey
Cream‐ high fat liquid product that is separated from whole milk
‐must be at least % milk fat
Butter‐ a dairy spread made from either sweet or sour cream
Margarine‐ made up of various fat ingredients that are churned with cultured, pasteurized
nonfat milk or whey
Cheese‐ concentrated dairy food defined as the fresh or matured products obtained by
draining the whey after coagulation of casein, the major milk protein
‐casein is clotted by coagulation enzyme rennin or by low p(
‐has many nutritional similarities of milk: high source of protein, calcium, phosphorus, and
vitamin A
C(ALLENGE
Phytochemicals: any plant derived substance that is thought to function in the body to
prevent certain diseases. They provide health benefits beyond what the standard nutrients
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provide and they are not members of the standard nutrient groupings because they are not
required for health
Herbs‐ medical herbs are plants or plant extracts that contain pharmacological or medicinal
substances herbal pharmaceuticals known as botanicals
Nutraceuticals: any healthy food ingredient produced from foods but sold in a pill or other
concentrated form, demonstrated to have a medical or physiological benefit not purely a
nutritional one
Functional Food‐ any food similar to a conventional food, consumed as part of a regular
diet that has demonstrated physiological benefits and/or reduces the risk of chronic disease
beyond basic nutritional functions
Unit : Food Regulating Agencies
Canadian Food Inspection Agency (CFIA)
‐ formed in April
‐ responsible for inspecting all food products sold in Canada, including imported products inspected
at point of entry
‐ brings together the inspection and quarantine services of (ealth Canada, Agriculture and Agri‐Food
Canada, and Fisheries and Oceans Canada
‐ while the "parent" agencies are still responsible for the development of new legislation, the CF)A is
now the main regulatory contact between the Canadian government and the food industry
Health Canada
‐ mandate is to protect the public from life threatening hazards in the food supply, in pharmaceuticals
and cosmetics, in medical or radiation emitting devices, and in the environment
‐ the (ealth Products and Food Branch has specific jurisdiction to monitor issues related to food
‐ deal with federal nutrition policy, domestic and international food regulations,
safety, natural health products, and food products sold
food
Agriculture and Agri‐Food Canada
‐ majority of CF)A inspectors are from this service
Food Additives
‐ defined by Canadian food regulations as "any substance, the use of which results, or may reasonably
be expected to result in it or its by‐products becoming part of or affecting the characteristics of food"
‐ nutritive materials, vitamins, minerals, spices, seasonings, flavourings, agricultural chemicals,
packaging materials, and veterinary drugs are NOT classified as additives
‐ regulated under Division
of the food and drug regulations in Canada
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Textbook Chapter 7
7.1 What is a food additive?
‐ a chemical or other substance that becomes a part of a food product either intentionally or
accidentally
Intentional Additives
‐ substances purposely added to perform specific functions; including sugar, salt, corn syrup, baking
soda, citric acid, and vegetable colouring
Indirect Additives
‐ contaminants
‐ substances that accidentally get into a food product during production, processing or packaging
Adulteration
‐ the deliberate addition of cheap ingredients to make it appear to be of high quality illegal in the US
Uses
‐ to maintain product consistency
‐ to improve or maintain nutritional value
‐ to maintain palatability and wholesomeness
‐ to provide leavening or control acidity/alkalinity
‐ to enhance flavour or impart desired colour
Principles Guiding the Application of Each Additive
‐ the safety of a food additive for human consumption must never be in doubt
‐ a food additive must function in food systems in accordance with its stated function under specific
conditions of use termed efficacy
‐ a food additive must not significantly diminish the nutritional value of the food in which it is
functioning, nor should it be used to compensate for improper manufacturing practices or inferior
product characteristics in a way that would deceive the consumer
‐ a food additive should be detectable by a defined method of analysis
Major Types
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‐ anticaking and free‐flowing agents
‐ keep ingredients in a powder form for ease of incorporation into formulations
manufacture
‐ antimicrobial agents
during
‐ inhibit the growth of bacteria, yeasts, and molds and function as preseratives
‐ antioxidants
‐ inhibit the oxidation of fats and pigments, which would otherwise result in product rancity
and altered colour
‐ colorants
‐ offset colour loss to due storage or processing of foods, or to correct for natural
in food colour
variation
‐ contain sodium nitrite, which helps retain the pink colour of cured meats, as well
as a preservative
as acting
‐ curing agents
‐ dough strengtheners
‐ improve the machinability if bread dough during processing
‐ includes emulsifiers
‐ emulsifiers
‐ keep fat globules dispersed in water or water droplets dispersed in fat
‐ important in butter, frankfurters, cakes etc.
‐ emulsifying salts enhance natural emulsifier activity
‐ enzymes
‐ biological catalysts that occur naturally in foods, used as beneficial additives
‐ flavourings
‐ may be natural or synthetic
‐ added for flavour production or modification
‐ flavour enhancers are used to make foods taste more delicious
‐ humectants
‐ attract water within a food product, which may lower the product's water activity
‐ leavening agents
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‐ enhance the leavening effect, rise, or "oven spring" of dough in baked products
‐ nutritional additives
‐ included in foods like cereals, baked goods, and drinks to boost nutrient intake
provide for a more balanced diet
‐ enrichment denotes the addition of nutrients lost during processing in order to
specific standard
‐ fortification is the addition of nutrients, either absent or present in insignificant
‐ nonnutritive sweeteners
and
meet a
amounts
‐ provide much greater sweetness intensity per amount when compared to sucrose
‐ nutritive sweeteners
‐ provide significant calories from carbohydrates in addition to a level of
intensity
sweetness
‐ occur mainly as residuals from application as sanitizing agents of food
equipment
processing
‐ oxidizing agents
‐ also act as bleaching agents to whiten food material such as flour
‐ p( control agents
‐ acidulants, which lower food p(, and alkalis or alkaline compounds, which increase food p(
‐ processing aids
‐ include not only acidulants and alkalis, but also buffers and phosphates
‐ added to help maintain a constant p( in food
‐ sequestrants
‐ combine with metal elements which are active in oxidation reactions
‐ by forming complexes with them, they inhibit the development of off‐flavours
odours due to oxidation
and
‐ combine with water in foods to increse product viscosity, to form gels, and to
product crystallization
prevent
‐ act as wetting agents, lubricants, dispersing agents, and emulsifiers by affecting
surface tension of materials present in food systems
the
‐ stabilizers and thickeners
‐ surface active agents surfactants
‐ added to foods during processing to reduce stickiness, promote mixing, improve
properties, and either destabilize foams or promote foaming
baking
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7.2 Food laws and regulations in the United States
The 1938 FFDCA and Amendments
Federal Food, Drug, and Cosmetic Act of 1938
‐ gave the FDA authority over food and food ingredients and defined requirements for truthful
labelling of ingredients
‐ required a standard of identity for several special foods
‐ detailed listing of the type and quantity of ingredients and means of preparation
‐ two other standards required are standards of minimum quality define minimum standards of
quality; texture, colour, etc. and standards of container full define how full the food container must
be and how it is measured
Food Additives Amendment of 1958
‐ requires FDA approval for the use of an additive prior to its inclusion in food
‐ requires the manufacturer to prove an additive's safety for the ways it would be used
‐ exempted two groups of substances from the food additive regulation process all determined to be
safe prior to this are called prior‐sanctioned substances; sodium nitrate and potassium nitrate
‐ second category excluded were "generally recognized as safe" GRAS
‐ salt, sugar, spices, etc.
substances
The Colour Additives Amendment of 1960
‐ requires dyes used in foods, drugs, cosmetics, and certain medical devices to be approved by the
FDA prior to marketing
The Delaney Cause
‐ provided by both the food additives and colour additives amendments
‐ prohibited the approval of an additive if it was found to cause cancer in humans or animals
‐ over time, it led to the cancellation of eight additives; a veterinary drug, a veterinary feed additive, a
flavouring agent, the sweetener saccharin, indirect food additives from packaging materials, and
several colour additives
‐ absolute in meaning, no grey areas zero‐tolerance
‐ laid to rest in
with the adoption of "negligible risk" to take its place
Other Legislation and Significant Regulatory Actions
Processed Foods Innovations
‐ during the
s to
s the processed food industry experienced a dramatic surge in growth
chemogastric revolution
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‐ all of these foods used new chemical ingredients and packaging, and they set stage for future
legislation concerning additives and manufacturing practices
‐ the Fair Packaging and Labelling Act of
of products
was passed to counter problems with underweighing
Pesticides and Toxicants
‐ passed in
, split jurisdiction for pesticides between the USDA could register pesticides for
specific uses and the FDA charged with setting tolerances for residues in raw agricultural products
Cyclamates
‐ alternative sweetener used in beverages
‐ banned in
mice
because tests concluded that a saccharin/cyclamate mixture caused cancer in lab
Saccharin
‐ this sweetener had been included in the original published list of GRAS substances but removed in
‐ the final rule, in
, prescribed limitations on the amount allowed per serving of food
‐ experimental data showed it to be a carcinogen in rats and FDA proposed to ban it
‐ congress passed the Saccharin Study and Labelling Act in
study
, which initiated a moratorium for
Red Book
‐ published in
, officially known as Toxicological Principles for the Safety Assessment of Direct
Food Additives and Color Additives Used in Food
Nutritional Labels
‐ under the Nutrition Labelling and Education Act NLEA , the label on almost every food product in
the US was changed
‐ some health claims were authorized, food ingredients and nutritional content panels on labels were
standardized, serving sizes were standardized, and terms such as low‐fat and light were standardized
Biotechnology
‐ FDA published its original biotechnology policy in the Federal Register in
‐ stated that it would focus on the safety of a food and not the process by which the food was
developed
7.4 The approval process for food additives
Testing Additive Safety
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‐ there are specific toxic effects investigated
‐ teratogen refers to a substance that causes abnormal fetal development and birth defects
‐ mutagens cause a change mutation in the base sequence of a cell's DNA, can
induce tumors and other forms of cancer
‐ carcinogens cause cancer in a test animal
also
Ames Test
‐ identifies the mutagenic potential of chemical substances
‐ uses a bacterial strain of Salmonella typhimurium that has a defective gene that prevents it from
being able to make the amino acid histidine from the ingredients in its culture medium they die from
this
‐ the presence of a mutagen reverses this
7.5 The nutrition labelling and education act (NLEA) of 1990
The Nutrition Facts Label
‐ contains serving size, quantitative amount per serving of each nutrient except vitamins and
minerals, amount of each nutrient except sugars and protein as a percent of the daily value for a
calorie diet, and a footnote with daily values for selected nutrients based on
and
calorie diets
General Product Labelling
‐ the following is presented in addition to the nutrition facts label
‐ product name and place of business
‐ product net weight
‐ product ingredient contents
‐ company name and address
‐ product code bar code
‐ product dating if applicable
‐ religious symbols if applicable
‐ safe handling instructions if applicable
‐ special warning instructions if applicable
Nutrient Content Descriptors
‐ only certain terms may be used
‐ percent fat free
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‐ product must be low‐fat or a fat‐free product
‐ healthy
sodium
or fibre
‐ fresh
‐ food low in fat and saturated fat and containing limited amounts of cholesterol
‐ must provide at least
% or more of one or more vitamins A or C, iron,
and
calcium, protein,
‐ food that is raw, has never been frozen or heated, and contains no preservatives
Health Claims
‐ any claim on a food label that expressly, or by implication, characterizes the relationship of any
substance to a disease or health‐related condition
Soluble Fibre from Whole Oats and Coronary Heart Disease
‐ the soluble oat fibre component beta‐glucan has been shown to reduce cholesterol
‐ FDA approved a health claim for rolled oats, oat bran, and whole oat flour
Soy Protein an Coronary Heart Disease
‐ FDA concluded that foods containing soy protein included in a diet low in saturated fat and
cholesterol may reduce the risk of C(D by lowering blood cholesterol levels
‐ FDA authorized the use of these health claims
Plant Sterol and Stanol Esters and Coronary Heart Disease
‐ FDA concluded that plant sterols esters and plant stanol esters may reduce the risk of C(D by
lowering blood cholesterol levels
‐ approved the use of these health claims
7.6 The dietary supplement health and education act of 1994
‐ changed the definitions and regulations for dietary supplements
‐ traditionally, the FDA considered dietary supplements to be composed of only essential nutrients,
such as vitamins, minerals, and proteins
‐ this act added herbs or similar nutritional substances
‐ formal definition
‐ a product other than tobacco that is intended to supplement the diet that bears or
contains one or more of the following dietary ingredients: a vitamin, mineral,
herb or other
botanical, amino acid, dietary substance for use by man to
supplement the diet by increasing total
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daily intake, or a concentrate, metabolite,
ingredients
constituent, extract, or combination of these
‐ intended for ingestion in a pill, capsule, tablet or liquid form
‐ not represented for use as a conventional food or as the sole item of a meal or
‐ labelled as a dietary supplement
diet
‐ includes product such as an approved drug, certified antibiotic, or licensed biologic that was
marketed as a dietary supplement of food before approval, certification, or license
Safety Testing
‐ vitamin and mineral supplements are regulated much like foods, but the other categories are not
‐ they are not seen as drugs and so are not subject to the same vigorous safety testing
Challenge!
Functional Foods
‐ current FDA approach to functional foods asks a number of questions
‐ what is the public perception of the product
‐ is it sold in a conventional market or in a limited, controlled markets
‐ is the manufacturer trying to skirt existing regulations
‐ is the product really a drug masquerading as food
‐ does it pose a hazard
‐ case A: Benecol
‐ the FDA wanted to see proof that the Benecol cholesterol‐lowering margarine
was safe,
but the creators responded by saying it was a dietary supplement, not
food, so it did not
require FDA approval
‐ the FDA then cited a law saying dietary supplements cannot masquerade as
‐ contains plant stanol ester
foods
‐ was deemed safe by the FDA
‐ case B: Vitamin O
‐ Federal Trade Commission warned that health claim ads were false, and that it
contained little more than saltwater
‐ ads claimed the supplement could cure or prevent cancer, heart disease, and lung disease
‐ scientists believe the placebo effect is at work here
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‐ the creators ended up being prohibited from making such claims
Bioengineered Foods
‐ genetically modified foods
‐ FDA published a "Statement of Policy: Foods Derived from New Plant Varieties", which stated that
there was no basis for concluding that bioengineered foods differ from other foods in any meaningful
way many of these foods are not labelled
‐ pre‐market review
‐ the FDA does not require consult when developing new foods, but it encourages
has received cooperation from the food industry
‐ FDA is currently moving towards tighter regulation
it and
‐ labelling
‐ the terms "derived through biotechnology" and "bioengineered" are acceptable
‐ "GM free", "GMO", and "modified" are not acceptable
Organic Foods
‐ the first set of quality and production standards for organic foods was developed under the Organic
Food Production Act of
‐ under these regulations, organic refers to food production practices that avoid most synthetic
pesticides and fertilizers, genetically modified crops, antibiotics in livestock production, irradiation,
and using sewage sludge as fertilizer
‐ the Agricultural Marketing Service AMS of the USDA published final regulations on procedures for
organic food production as the National Organic Program final rule in the Federal Register
‐ increased the minimum percentage of organic ingredients in the products labelled from
percent
to
‐ utilized the EPA's percent pesticide residue tolerance as a compliance
‐ in
tools
threshold
‐ allowed wine containing sulphites to be labelled "Made with Organic Grapes"
it was required to display the USDA organic seal on products certified others are marketing
Unit : Food Chemistry‐ Major Components
Part
Chapter –pg.
Review 4.1 – 4.3
‐
4.1 The Nature of Matter
o
Foods are made of matter –matter is made up of pure substances ‐elements or compounds
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Elements: simplest type of pure substance that have mass and cannot be broken down
into something else
o Compounds: two or more elements chemically bonded together in definite
proportions by weight
 )mportant compounds in food science are called organic compounds
 Contain carbon, hydrogen, oxygen and sometimes sulfur, nitrogen and
phosphorus
o Chemical symbols, formulas and equations
o Symbols
 Represent elements of the periodic table
 Use chemical shorthand in describing rxns between food and components
o Formulas
 All elements in a compound make up the formula
 Chemical symbols are combined to define chemical formulas
 Subscripts indicate proportion of elements
o Equations
 Written description of a chemical reaction using symbols and formulas
 Reactants are on the left side of a yield arrow and products to the right
o Electron Orbits and Chemical Bonds
o Chemical bonds: forces that hold atoms together
 Only electrons of reactant atoms are involve in the chemical bonding event
not protons or neutrons
o Chemical Bonds in Food
o Covalent bonds
 Sharing one or more pairs of electrons so that each atom can fill its valence
shell
 Single covalent bond is formed when one pair of electrons is shared
 Double bond: two pairs of electrons are shared between molecules
o )onic bond
 Filling of valence shells through transfer of electrons
o (ydrogen bond
 Kind of covalent bond but there is unequal rather than equal sharing of
electrons between bonding atoms
o )ntramolecular bonds‐ bonding within the same molecule
o )ntermolecular bonds: bonds between two diff molecules
4.2 Chemical Reactions in Foods
o
o
o
Classified as either composition or decomposition reactions
o Composition reaction: two or more substances are combined into a single product.
A+BAB
 )mportant macromolecules in food are produced this way in nature and
processing
o Decomposition reaction: opposite of composition. AB  A+ B
 Describes how food macromolecules come apart during processing conditions
or by enzyme action
Enzymatic Reactions
o Enzymes occur in living systems only ex. plant and animal tissue also present in
microorganisms that are found in food
o Enzymes can cause quality changes in food color, texture, flavour and odour during
storage and use
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Softening of texture and browning of fruits are undesirable effects of enzyme
activity
 Food industry takes advantage of desirable enzymatic reactions carried on by
bacteria to produce fermented foods like cheese, teas and yogurt
o Enzymes: protein molecules –polypeptides composed of amino acids
 Biological catalysts
 Cause chemical reactions to speed up
 Catalyze reactions specific for particular substrates
o Enzyme that breaks down starch into glucose will not work on
protein
o Catalytic activity occurs on active site –where substrate joins with enzyme to form
enzyme substrate complex
 Reactivity of this site is governed by functional groups present there
o Activation Energy and How an Enzyme Works
o Activation energy: amount of energy needed to convert substrate molecules from
ground energy state to ES enzyme substrate complex
o Enzymes work best under certain conditions temperature, p( and amount of
substrate present
o Amount of substrate must be kept as high as possible to create zero order reaction
 Enzymatic (ydrolysis
o )n these reactions, an enzyme breaks large food molecules into smaller fragments
 Carbohydrases Sucrase, lactase, maltase, amylase , protease, lipase
 Function in food fermentation reactions carried out by microorganisms
 Fermentation: original food molecules are changed and converted into
fermentation products
o Carbohydrate fermentation leads to lactic acid, acetic acid,
ethanol and CO
o Enzymatic Oxidation‐Reduction
o Enzyme causes changes in the chemical structure of food molecules
o Enzymatic oxidation reactions: occur when oxygen is added to or hydrogen or
electrons are removed from food molecules in the presence of an active enzyme
o Browning of fruits and vegetables –enzymatic oxidation
 PPO polyphenol oxidase enzyme responsible for formation of brown
oxidized pigments in apple/banana slices exposed to air
 Original pigment molecules react with oxygen and are transformed into
brown melanin pigment molecules
o Enzymatic Polymerization
o Condensation: separate reactant molecules can be joined through action of enzymes
 Results in generation of small molecules like dipeptides and disaccharides or
larger polymers
o Polymer: high molecular weight molecule created by repetitive reaction of
hundreds/thousands of low molecular weight units
o Polymerization: type of reaction in which many molecular units monomers are joined
together ened to end
Nonenzymatic Reactions


Chemical reactions in food that do not depend on enzymes include the following:
o Addition: take place in organic molecules that possess double or triple bonds between
carbon atoms
 (ighly reactive bonds
 )n foods, double bonds are found in unsaturated fatty acids
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
Addition of hydrogen to fat creates an addition reaction where double
bond is broken, and hydrogen is incorporated into fatty acid structure
o (ydrogenation of fat
o Used to make margarine
o Oxidation and Reduction
 Electrons are transferred between substances
 Significant because they affect colour, quality and acceptability of
foods
 Oxidation: Addition of oxygen –oxidizes carbon atoms
 Reduction: gain of hydrogen –reduces carbon atom
 Reducing agent: substance that causes another substance to become reduced
 Reducing agent itself becomes oxidized
 Ex. food antioxidants
 Oxidizing agent substance that causes another substance to become oxidized
 Oxidizing agent becomes reduced
 Ex. dough conditioners/flour‐bleaching agents
o Condensation and (ydrolysis
 Condensation: separate reactant molecules are linked together by special
chemical bonds
 Reactant loses hydrogen and oxygen atoms which combine through a
side reaction to form water
 (ydrolysis: water molecule enters region of functional group of a larger
molecule and splits it off
 O( group of water molecule attaches to one of the newly split‐off
molecule pieces and hydrogen attaches to other
4.3 Functional Groups
o
Functional groups: arrangements of just a few atoms that create particular properties of
molecules
o Alcohol group O( –hydroxyl group
 Does not ionize
 Ex. glycerol –derived from animal fats and vegetable oils
 Food alcohol: ethanol can be produced by hydrolyzing starch in potatoes or
fermenting sugars in molasses
o Aldehyde group
 Aldehyde –oxygen molecule is double bonded to carbon
 Ex. formaldehyde
o Amino group
 N( group called an amine
 Derived from ammonia –basic substances gaining protons in chemical
reactions
 Food amines are produced by bacterial action ex. dopamine
o Carboxylic Acid group
 COO( functional group
o Ester Group
 Carbonyl oxygen carbon system
 Animal fats and corn oil are esters of fatty acids attached to glycerol
 Present in fruits and give characteristic flavours and aromas
 Combining acid and alcohol dehydration synthesis –synthetic food flavours
made this way
o Ketone Group
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Organic compounds where an interior carbon atom is double bonded to
oxygen atom
o Methyl Group
 Methyl group transfers are important in biosynthesis of certain bioactive
compounds
 Plant pectin s and gum contain methyl groups contribute to functional
properties such as viscosity and gelation
o Phosphate Group
 Salts of phosphoric acid making it a noncarboxylic acid
 Resembles a phosphate group except it has a double bond between the
phosphorous and one of the oxygen atoms –remaining oxygen atoms
are bound to phosphorous
 Orthophosphates used in meat to improve texture, juiciness
o Sulfhydryl Group
 Similar to an alcohol group
 Called thiols
 Easily oxidized and yield disulfides
o )onic groups
 Variety of atoms exist as ions –carry negative and positive charges
 Play a crucial role in foods influencing food quality
4.4 The Chemical and Functional Properties of Water (Testable material from here onwards)

o
o
o
Functional properties: physical and chemical properties of food molecules that affect their
behaviour in foods during formulation, processing, and storage
o )nclude sensory and mechanical properties of food ‐flavour, texture, effects on water on
the physical condition of the final product
o Depends on hydrogen bonds
o Functional properties of water in foods include:
 Dilutent and carrier or hydrophilic food ingredients
 Medium for chemical and enzymatic reactions
 Dispersing
 Solvent action
o Water serves as a fat replacer and zero‐calorie ingredient
 Component of gels and emulsions
 Medium for heat transfer
 Plasticizer
 Food moisture
 Reactant/product in chemical reactions
 Condensation/hydrolysis
Water Molecule Structure
o One water molecule has:
 Two hydrogen atoms bonded to an oxygen atom
 (ydrogen shares an electron pair with oxygen
 A charge separation results dipole in which the oxygen atom has a partial negative
charge while the hydrogen atom ahs a partial positive charge
 Dipolar nature of water affects its physical characteristics
o Boiling point
o Freezing point
o Vapour pressure
Solvating an Dispersing Actions
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Compounds that hydrogen bond easily to water to form solutions or colloidal dispersions
are called hydrophilic compounds
 Charged or polar molecules
o (ydration: process by which water molecules surround and interact with solutes by acting
as a solvent
o Water disperses amphiphilic molecules
 Amphiphilic molecules: contain both hydrophilic and hydrophobic regions in their
structures ex. Proteins, certain vitamins and phospholipids
 Form micelles in water
 Clusters of molecules in which the hydrophobic groups are directed away
from the water while the polar groups are exposed on the external surface
 Nonpolar hydrophobic groups form a stable inner core
 )nteractions among water molecules and between water and food molecules are called
noncovalent interactions
 )mportant in food chemistry and include hydrogen bonding, ionic interactions
ions in water and hydrophobic interactions micelles
Water Activity and Moisture
o Water exists in one of several forms in food
 Each form is the same but differences exist in physical and chemical conditions in
which water an exist
o Presence of water in food is described as moisture content or water activity of the food
 Moisture: absolute amount of water present in a food as a component relative to all
solid constituents proteins, carbohydrates and nonwater liquid
 Most water is called free water
o Lightly entrapped and easily pressed form food matter
o Acts as a dispersing agent and solvent and can be removed by drying
foods
 Water activity: form in which the water exists in the food free/chemically bound
 Measure of availability of water molecules to enter into microbial, enzymatic
or chemical reactions
 Availability determines shelf life of a food
o Absorbed water/structural water
 Associates layers via intermolecular hydrogen bonds around hydrophilic food
molecules
o Bound water/water of hydration
 Third form of water in food
 Exists in a tight chemically bond situation ex within a crystalline structure via water
ion and water dipole interactions
 Does not exhibit typical properties of water does not freeze at degrees and does not
act as a solvent
 As bound water % in a food increases, water activity decreases
 Calculated as the ratio of water vapour pressure of substance divided by vapour
pressure of pure water at the same temperature:
 Aw = P/P
 P = vapour pressure of the food
 P = vapour pressure of pure water at the same temperature
 Water activity of pure water is . according to this equation
 Water activity is a measure of relative humidity
 Multiplying Aw by
, the relative humidity R( of the atmosphere in
equilibrium with the food R( % is obtained
o R( % =
x Aw
o
o
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Moisture sorption isotherms are graphs of data that interrelate the water content of food
with its water activity at a constant temperature
 )ndicates water activity at which a food is stable and allows predictions of effect of
changes in moisture content on Aw and storage ability
 Determine rate and extent of drying, optimum frozen storage temperature, and
moisture barrier properties required in food packaging materials
o Water as a Component of Emulsions
 Emulsion: type of colloidal dispersion –system containing two liquids or phases that
normally do not mix: a dispersed and continuous phase
 Water –aqueous component of emulsion –can be dispersed and continuous phase
 Water phase of an emulsion is hydrophilic
 Fat phase is lipophilic
o Water and heat transfer
 Water is important for heat transfer in food during food processing operations and
food preparations
 (eat transfer: water is able to act as a conductor of thermal energy to food molecules
o Water as an Ingredient
 Water is oftentimes incorporated into processes foods
 )ncreasing amount of water in food can reduce quality b/c water can act as a solvent
and change state w temperature
 Stabilizing movement of water is desirable in frozen foods
 Freeze thaw cycles in stored foods result in production of concentrated and
diluted portions of a previously homogenous food product when freeze thaw
stability is poor
4.5 The Chemical and Functional Properties of Food Acids
o
o
o
Food Acid Structure
o Typical food acid is carboxylic or organic acid containing carboxylic acid group
attached to remainder of molecule
o Food acids differ in where group is located and number/arrangement of the other
carbon hydrogen and oxygen atoms in the structure
 Differences influence physical and chemical properties
 Acids lacking carboxylic acid group phosphoric acid are inorganic acids
o Functional properties of food acids influence flavour and act as antimicrobial agents
 Some are added to intensify sweet flavour
 Add sour flavour to baked/dairy products
o Some foods/ingredients must remain free‐flowing and have acids added to them b/c
acids exhibit low hygroscopicity
 Low attraction for moisture
 W/o it, could result in clumping of ingredients due to moisture pickup
o Number of carboxylic acid groups in their structures creates differences in functional
properties
 May cause them to behave differently
Acid Strength
o Food acids donate protons
o Weak acid: mainly in the form of –COO( but a small amount of (+ separated or
dissociated to form COO‐ + (+
 Small dissociation or ionization constant Ka
 Ka: (A <‐> (+ + A‐
 (A‐ ionized acid
 (+ proton
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o
o
o
o
o
 A‐ conjugate base or anion of original acid
 Strength of an acid is proportional to its Ka value
o Strong acids: large amount of dissociated ions
 Small dissociation is critical on effect on p(, which affects food properties like
sweetness, sourness, flavour etc.
pKa of an acid also measures strength
o Lower pKa the stronger the acid b/c pKa is the inverse of Ka
Fumaric Acid and Dough Softening
o Fumaric acid can soften products like flour dough s
 Wheat flour contains proteins which contain the amino acid cysteine –possess
Sulfhydryl groups in the reduced –S( form
 Sulfhydryl groups become oxidized losing hydrogen
 Remaining sulfur atoms on each cysteine can join forming disulfide bonds
between cysteine amino acids in flour dough proteins
 Bonds allow for tightening of dough structure
 )f Fumaric acid is added to dough formulation breaks disulfide bonds
and a softer more easily manipulated dough results
o This is b/c carboxylic acid groups in Fumaric acid establish
reducing conditions by donating (+
o (ydrogen adds to the sulfur atoms in the disulfide bonds,
converting them back to –S(
Salts of Organic Acids
o Organic salts: compounds formed from organic acids
 (ydrogen atom of COO( is replaced by a metal ion such as sodium, calcium, or
potassium
o When organic salts ionize, they produce ions other than hydrogen ions or hydroxide
ions
 Technically they are not behaving as acids or bases
Buffers
o Buffer: solution of a weak acid and its salt at a p( where the solution ahs the ability to
maintain that p( when quantities of base are added
o Buffering action of any acid/salt system is limited to a p( range extending one half p(
unit on either side of the pKa of an acid
Leavening
o Leavening: production of gas by yeast fermentation by reaction of an acid with baking
soda in batter and dough products or by the heating of salts
 Key to leavening effect is the production of gases that create expansion in the
product
 Variety of gasses alone/in combination create expansion in product
 Ex CO , air, ammonia etc.
o Leavening acids: useful participants in food leavening systems used for baking
 Acids generate hydrogen ions that facilitate the release of carbon dioxide from
baking soda
 Gas release causes the expansion of a baking dough or batter product
due to the increase pressure inside of the gas nuclei
o Critical properties of leavening acids:
 Neutralizing value NV : amount of sodium bicarbonate that can neutralized
by
parts by weight of leavening acid
 Dough reaction rates refer to the speed of reactivity of a leavening acid in a
dough as the amount of carbon dioxide released
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Baking powder is used alone without adding leavening acid b/c it is a mixture of
baking soda and acid
 When hydrated in cold liquid, the acid releases CO from the soda
o Double acting powder SAS phosphate reacts twice
 First reaction releases carbon dioxide in the dough through reaction of MCP
monocalcium phosphate monohydrate acting as the acid in water w/ baking
soda
 Second reaction requires SAS to be converted into an acid in order to release
carbon dioxide from baking soda
 SAS is heated in the presence of water and converted into sulphuric
acid which reacts w/ baking soda to release carbon dioxide during
baking step
4.6 Food Acidity
o pH and the pH scale
 p(: hydrogen ion concentration expressed on a logarithmic scale, of the free
or dissociated hydrogen ions in a product
 Calculated by using the formula p(=‐log[(+]
 Relative number of (+ and Oh‐ ions present in a solution is measured on the
p( scale
 Scale reflects concentrations of these ions in a solution
 Foods with p( values lower than are acidic
o p( values higher than are basic or alkaline
o Those w/ a p( of are neutral
o Low values indicate high (+ concentration opposite for high values
Titratable Acidity
o Measure of the total acidity in a sample both as free hydrogen ions and hydrogen ions
still bound to acids
 Measured by careful additions of a base of known concentration to the sample
until a predetermined end point is reached
 Used to measure amount of base required to neutralize components of a given
quantity of milk and milk products and is expressed as a percentage of
dominant acid which is lactic acid
 End point may be an indicator color change at a particular p(
 Measuring Titratable acidity monitors progress of fermentation
 Fermentation: breakdown of carbohydrates into sugars and acid is essential
for cheese and fermented milk quality
o Lactic acid in milk is formed by:
 Lactose sugar present in milk by bacterial fermentation
 )f bacteria are present in milk there can be an undesirable souring of the taste
due to the fermentation reaction
 Controlling microbial activity in milk is important for dairy manufacturing
 Raw milk must be pasteurized –head treatment to kill microorganisms and is
kept free of microbes and lactic acid they would generate
o )mportant to know stage of maturity of fruit in fruit industry
 Determining Titratable acidity provides information b/c the relative
predominance of acids shifts during ripening and maturity
p( and Acid foods
o Acid food: one that has a natural p( of . or below
o Natural p(: p( prior to processing
o Acidified foods: low acid foods to which acids are added –exceed ,
o
o
o
o
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o
o
o
Challenge!
Low acid foods: are foods having an equilibrium p( greater than . and water
activity .
Equilibrium p( is the condition achieved when the solid and liquid parts of the
product have the same p(
Fermented foods: low acid foods subjected to the action of certain microorganisms
 Microorganisms produce acid during their growth and reduce the p( of the
food to . or below
 Partially fermented foods requiring addition of acid to reduce the p( to . or
less are also considered acidified foods
Food Systems

Food is matter divided into categories:
o (omogenous matter and heterogeneous matter
 (omogenous matter: uniform composition throughout
 )ndividual components cannot be visually discerned
 Ex. solutions
o (eterogeneous matter: individual components can be visually discerned and may be
distributed unevenly
o Foods are mixtures composed of solid, liquid and gas phases that are dispersed
 Behaviour of food systems during processing and storage depending upon
their phase makeup
Food System Stability and Texture
o
o
o
o
o
Functional properties of food macromolecules and ingredients in such systems affect their
physical stability
o Emulsifiers and stabilizers are added to food systems to maintain phase stability
Texture: quality characteristic of major importance influenced by the functional properties of
food macromolecules and ingredients within food systems
Key to understanding food systems is notion of particle size
o Three basic dispersion types based upon particle size in solutions:
 Colloidal dispersions particles ‐
nm in diameter
 Suspensions large particles that remain suspended in continuous phase
Solutions
o (omogenous mixtures in which one substance solute is dissolved in another
 Solvents can be solids, liquids or gases but in foods they are almost always
liquid water
 Ex. coffee, tea, cold beverages etc.
o Solubility: maximum amount of solute that dissolves in a specified volume of solvent at a
specified temperature
 Temperature has a significant effect on solubility –effect depends on whether
system consists of a gas solute or solid solute
 Solubility of most solids increases when temperature is raised
Food Colloids
o Surface active ingredients such as fatty acids, glycerides, phospholipids, polysaccharides
and proteins
 Colloid is a particle that is too large to dissolve and become the dispersed
phase of a true solution
 Become components of colloidal dispersions
 May exist as charged particles or clusters called aggregates
o Colloidal dispersions include emulsions, foams, gels and sols
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o
o
o
o
Emulsions
o Colloidal dispersion of two liquids usually oil and water that are not mixable
 Oil dispersed in water called an oil in water emulsion O/W
 Water dispersed in oil is called a water in oil emulsion W/O
 Butter is a W/O emulsion that contains two liquid phases that are allowed to
solidify
 Raw unprocessed milk is an unstable O/W emulsion because it contains large
fat globules that clump together and rise to layer on top of the water phase
 Called creaming
Emulsion stability: )nteractions are key
o )nteractions that take place in food systems include emulsions
 )nteractions include:
 solvent:solvent
 solute:solute
 solute:solvent
o )n O/W emulsions, water and oil do not repel each other the way opposite magnet poles
do
 )ndividual oil molecules are actually attracted to water molecules by a force
that is much greater than the attraction of two oil molecules to each other
 Net cost of energy in putting al the oil molecules into a water solution is too
large b/c the force of water to water attractions is greater than water to oil
attractions
 Result is merging of oil droplets until separation of phases is achieved
 Unstable food systems
 With a addition of surface active molecules the phases can be
stabilized
o Emulsifiers
 Amphiphillic molecules: contain hydrophilic and hydrophobic regions in their
structure
 Thickening agents act to increase the viscosity of the continuous phase of an
emulsion which enhances emulsion stability by inhibiting droplet merging
and phase separation
Foams
o Dispersed phase is a gas within a liquid continuous phase
o Metastable not permanently stable
o Achieves equilibrium under force of gravity through the process of drainage of liquid from
the foam
 Surfactants and proteins inhibit drainage by different mechanisms
o )n whipped cream, air is incorporated into cream and the milk protein in the system acts
as an emulsifier to trap the tiny air cells
 (igh viscosity and low surface tension of the liquid phase of this system
favours a stable form formation
Gels and Sols
o Gel: two‐phase system in which a liquid is dispensed in a solid
o Colloidal gels form when colloid molecules or particles associate in a liquid such that the
solvent becomes immobile
o Food gels are composed of concentrated polymer solutions that form three dimensional
networks
 Diffuse into polymer networks where it becomes entrapped
 Polymers cannot diffuse out from a strong gel, if the gel breaks weak gels
polymers can come out of the solution
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o
o
Formation of food gels is based upon the functionality of either a polysaccharide or
protein gelling agent
 Polysaccharides such as gums, pectin s and starches are examples of gelling
agents
 Legume proteins can be coagulated by heat, acid or enzymes prior to setting
into a tofu gel
 Salt‐soluble meat proteins are able to form gels
 Other animal proteins such as gelatin can form gels
Sol: a solid dispersed in a liquid
 Ex. gravy
 Starch suspension in water becomes a sol when heated due to gelatinization
 When cooled a gelatinized starch sol converts into gel
 Starch gel is a thickened sol that is no longer pourable b/c it has developed a
solid continuous phase
Chapter 5 –Food Chemistry II: Carbohydrates, Lipids, and Proteins
5.1 Food Carbohydrates
The Structures of Sugar
o
o
o
o
All carbohydrates contain the elements: carbon, hydrogen and oxygen
o Basic building block of all carbohydrates is simple sugar
 Can include fructose and glucose single carbohydrate units
 Sucrose and lactose are composed of two carbohydrate units joined together –
disaccharides
 Simple sugar is called an organic alcohol since it is a molecule that contains
carbon atoms attached to –O(
 Classified on the basis of the number of sugar units they possess
 )n foods carbohydrates exist as monosaccharide s, disaccharides,
oligosaccharides or polysaccharides
Monosaccharides
o
carbon atoms in their structure –called trioses

carbon atoms –pentoses, carbon atoms –hexoses
 )mportant monosaccharides found in foods are hexoses glucose, fructose and
galactose
 (ave identical chemical formulas but slight differences in location of
the functional groups cause differences in functional properties
including sweetness and solubility
 Glucose: most common monosaccharide in foods
 Grapes, berries –contain ‐ % glucose
 Glucose is considered an aldose b/c of its carbonyl group
 Fructose is considered a ketose b/c its carbonyl group at carbon atom is in
the form of a ketone
 Galactose is the only other food monosaccharide and occurs in disaccharide
lactose
Monosaccharides exist in more than one structural form –straight chain or Fischer projection
molecules and ring/cyclic (aworth projection
)n solution ring form predominates b/c functional groups at carbon and carbon undergo
an intermolecular cyclization reaction which joins C and C to form a closed ring
o Eliminates carbonyl group leaving O( group instead
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o
o
o
o
o
o
o
Disaccharides
 Two Monosaccharides joined together form a disaccharides
 Joined by a glycosidic bond
 Three important food disaccharides are sucrose, lactose and maltose
 Sucrose: composed of glucose + fructose table sugar used in food
preparation in crystalline form
 Lactose: composed of glucose and galactose is found only in milk and dairy
products
 Maltose: two glucose units
The Functional Properties of Sugar
o Sugar molecules contain two important reactive functional groups:
 Carbonyl group and the alcohol group
 Alcohol group is important for solubility and sweetness
 Present in multiple locations on sugar molecules
 Readily form ( bonds with water making glucose molecules very
soluble
 Carbonyl group is important for reducing activity and the Maillard browning
reaction causes color/flavor changes
 Other sugars are either more or less soluble than glucose
Reducing Sugars
o Sugars that contain aldehyde/ketone carbonyl group are called reducing sugars
 React w/ other substances through oxidation‐reduction chemistry to produce
a reduced substance plus oxidised sugar molecule
 All monosaccharides and some disaccharides are reducing sugars
o Dextrose equivalent: measure of the percentage of glycosidic bonds hydrolyzed in
disaccharides and polysaccharides which indicates level of reducing sugar present
Browning
o Maillard browning and carmelization are important browning reactions that occur
in sugars
 Reducing sugars react with the amino acids through the Maillard reaction to
produce brown color pigments in food
 Maillard browning is browning of foods as a result of the Maillard reaction and
the brown pigments that form are called melanoidins
 Maillard reactions are not always negative –pleasant aroma of baked bread is
due to this reaction
o Maillard reaction can be viewed as a sequence of chemical reactions
 Condensation, rearrangement and polymerization
 Non‐enzymatic browning b/c enzymes are not part of rxn –complex sequence
of chemical reactions
 For reactions to begin, sugar molecule must have a free carbonyl group and an
amino group must be present in the reaction mixture
. Condensation
o Reducing sugar + amino group <‐> glycosylamine
 Location of reactive site on sugar molecule aldose sugar/glucose is at C and
ketose sugar is at C
. Rearrangement
o Glycosylamine <‐> Amadori compounds (colourless)  pyrazines
 Color and flavour development begins at this stage
 Degradation of Amadori compounds favors formation of furfurals –cyclic
aldehydes in the form of the membered ether ring
. Polymerization
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Colourless intermediate compounds <‐> brown melanoidins
 Generates the large molecular weight melanoidins
 Polymerizations are irreversible and eventually result in significant darkening
of food
 Unpleasant tastes/aroma may develop
 Excessive product moisture loss
Amino acids having extra amino group in their side chain structure such as lysine are better
substrates in the initial Maillard reaction than others
Maillard browning is also accelerated by lower molecular weight sugars
Free amino acids are more reactive than peptides
Caramelization: formation of brown caramel pigments as a result of applying heat energy to
sugars
o Temperature required is
degrees C
o Protein material including enzymes is not required
o Caramel colouring refers to a brown color additive used in the food industry
whereas caramels refers to sauces or candies made from carbohydrates that have
been allowed to caramelize
Crystallization
o )mplies organized D arrays of unit cells into a solid form
o Depends on factors such as the moisture, temperature and concentration of sugar in
a food system
o Crystal: solid made up of units in a repeating pattern
 Sugars crystallize in stages:
st stage: transfer of sugar molecule to surface of a crustal

nd stage: incorporation of sugar into crystalline structure

(umectancy
o (umectant: substance that has an affinity for moisture
o Carbohydrates and sugars are used as humectants ingredients in the food industry
 Effective in influencing the state of water in food systems
o (umectants hydrogen bond with water molecules making water less available for
microbial growth
)nversion
o (ydrolysis of sucrose to its component monosaccharide is carried out if a sweeter
product is desired than when sucrose is present alone as a product
 Mixture of two monosaccharide end products called invert sugars is created in
food products through application of the enzyme invertase
Oxidation and Reduction
o Oxidation of aldehyde group in sugars causes a loss of sweetness and converts the
aldehyde to an acid group
Sweetness and Texturizing
o Each monosaccharide and disaccharide differs in sweetness
 Relative sweetness is in comparison to sucrose
o Sugars control amount of water available as free, adsorbed and bound water
 Affects food texture, shelf life and microbial growth
o Competition between sugars and other substances in food for water affect food
texture
Polysaccharides and their functional properties
o Complex carbohydrates of
or fewer sugar units are called oligosaccharides
o Polysaccharide molecules are usually at least
or more sugar units in size
 Often contain reducing and non‐reducing areas in their structures
o
o
o
o
o
o
o
o
o
o
o
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)mportant b/c non‐reducing ends of carbohydrates are susceptible to enzyme
attack
o Sugars can exist as alpha and beta
 Differ whether O( group attached to first carbon atom projects downwards
alpha or upwards beta
 Linkage is a if O( of first carbon atom of sugar unit is pointing down
Beta‐glucans
o Polysaccharides of glucose similar to cellulose but less linear
 Lower cholesterol and activate immune system
o Beta , glucan is derived from the cell wall of yeast
Cellulose
o Most abundant of carbohydrate polymers
o Compose plant cell wall material
o Consist of linear chains of glucose joined by beat , glycosidic bonds
Dextrins and Maltodextrins
o Dextrins: polysaccharides derived from starch linear arrays of glucose units bound
by alpha , glycosidic linkages
 Produced commercially by hydrolyzing especially the amylose portion of
starch
 Called dextrinization b/c heat is used to carry out reaction
 Products are called pyrodextrins
 Do not confuse dextrins w/ dextrans dextrans: another example of
polysaccharide w/ glucose units –bonding is alpha , glycosidic bonds
o Maltodextrins: polysaccharide fragments derived from starch hydrolysis
 Defined as having a dextrose equivalent DE of less than
 Lower DE the less sweet the carbohydrate
o Fructooligosaccharides
 Naturally occurring sugars consisting of multiple units of sucrose joined to
one/two/three fructose molecules via glycosidic bond to the fructose portion
of the sucrose molecule
 Known as prebiotics –promote the growth of probiotics bacterial
organisms beneficial for health
 Promote, stabilize and enhance the proliferation of these beneficial
bacteria into the gastrointestinal environment
 Pathogenic bacteria cannot use FOS
 May offer benefits such as: stimulate growth of bacteria, reduce fecal p(, toxic
metabolites, serum cholesterol and triglyceride levels
o )nsulin: Dietary Fibre
 )nsulin is a fructooligosaccharide that functions as a soluble dietary fibre
 Occurs naturally in plants
 Composed of a chain of fructose units with a terminal glucose unit w/
an average chain length of
 Not digestible
 B‐ , fructan
 Prebuituc and stimulates growth of beneficial bacteria
 As a food additive in low concentrations, forms vicious solutions
 at concentrations above % forms gel like substance
 )n reduced fat/nonfat systems, insulin provides a creamy mouthfeel through
texture modification
 Application in yogurt, cheese, frozen desserts etc
o Pectic Substances

o
o
o
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(igh molecular weight polysacccharides found in plant cell wall middle
lamellae
 Composed of galacturonic acid units joined by alpha , glycosidic linkages
 Some of the acid groups become methylated during fruit ripening –considered
to be esters of methanol
 Three chemically distinct substances have been identified
 Protopectin: nonmethylated galacturoinc acid polymers found in
immature fruit
 Pectinic acid: methylated galacturonic acid polymer produced during
ripening
 Pectic acid: short chained demethylated derivative of pectinic acid
associated with overripe fruit
 LM pectin: less than % of carboxylic acids esterified with methanol ‐
chemically modified pectin
 (M pectin has more than % of carboxylic acids esterified with methanol –
occurs naturally in fruits
Pectin/gelation
 Pectin s are able to form from colloidal dispersion, sols and gels –widely used
in food industry
 Pectin gels: systems containing a large volume of water within a D solid
network
 Remain dispersed in water due to attractive interactions between their
carboxylic acid and alcohol groups w/ water
 Conditions required for (M pectin gelation
 Addition of acid and addition of sucrose
 Acid reduces repulsive forces between polymers that keep them
dispersed in water
 Sugars act to reduce pectin solubility by interacting w/ water itself
lowering water activity of the system
o Decreases polymer:water interactions allowing for increased
polymer:polymer association
o Permits gel network to form
o Decrease in p( assists intermolecular associations between
adjoining pectin polymers in the network
 LM pectin
 Majority of carboxylic acid groups on the galacturonic acid polymers
are not methylated
 Allows for hydrogen bonding w/ water molecules through dipole‐
dipole interactions
 Carboxylic acid groups are free to ionize to produce carboxylate
groups which creates an abundance of negative charges and ion dipole
interactions w/ water
 Negative charges also repel LM pectin polymers apart
o Rxns act as a barrier to gelation
o When a metal calcium is added carboxylate groups can cross
link with oppositely charged ions pulling neighbouring LM
pectin polymers together
Starch
 Polysaccharide derived from plant sources
 Polymer of
+ glucose units

o
o
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(as branced amylopectin and unbranched amylose regions to its
molecular structure
 Starch polymers do not exist in the free state in plants
 Occurs as starch granules spherical aggregates
 Amount of amylose and amylopectin is important b/c the behaviour of heated
starch in water depends on whether source is high in amylose/amylopectin
 Starch loses function during food processing conditions –so certain heat or
chemical modifications are employed
 Modifications involve alcohol groups on starch polymer or glycosidic bond
cleavage
 Chemically modified starch ex pregelatinized starch
o Starch gelatinization
 Do not form true solutions w/ water b/c starch molecules are too large
 When starch is heated in water, bonds joining starch fractions amylose and
amylopectin are weakened/loosened allowing water molecules to move in
and form ( bonds
 During gelatinization, heated starch granules absorb water and swell in size
 )rreversible rxn
o Starch pasting and gel formation
 Starch paste: viscoelastic starch and water system that possesses both thick
liquid like and solid like properties
 Pasting process follows gelatinization
 Three changes in starch: swelling, exudation and disruption
 Majority of the starch granules have gelatinized producing swollen
and disrupted starch granules and exudative molecular matter
o Material migrates into the intergranule matrix region
between adjacent starch granules
 Gelation: formation of a gel from a cooled paste
 Starch gel: rigid, thickened starch and water mixture that has the
properties of a solid
 Starches w/ high amylose content form gels more easily than do
starches high in amylopectin
o Starch retrogradation
 After heating and cooling, starch polymers amylose and amylopectin and
intergranule matrix starch fragments can reassociate into an ordered
structure
 Represents a loss of entropy to the system –retrogradation
o Due to intermolecular hydrogen bond formation, between
linear amylose molecules
o )ncreased tendency to release water from cell called syneresis
occurs
Vegetable Gums
o Plant hydrocolloids
 Substances derived from plants that distribute in water as colloidal
dispersions
 Composed of loop chain polymers of various hexoses and pentoses
 (ydrocolloid polymers may be linear or branched
 Affects their functionality
 Branched molecules are not as able to interact w/ each other through
physical surface contact compare to linear polymers

o
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Side groups become entangled and they gel more easily than
linear hydrocolloids
Gums are noncaloric
 Makes them appropriate fat replacers in certain food applications
 Provide smooth texture act as thickeners and water binders
 )mportant in food processing as ingredients in reduced fat foods
o

5.2 Food Lipids
o Structures and Types of Lipids
o Fats and oils
 Chemically known as triacylglycerols/triglycerides
 Glycerol: ‐carbon molecule containing alcohol groups
 Fatty acids are organic molecules that contain chains of carbon bound to hydrogen
plus an acid group and methyl group at one end and the other
 Ester bonds hold fatty acids to glycerol joining O( groups of glycerol to COO( groups
of fatty acids w/ loss of water
o Saturated and unsaturated fats
 Fats and oils are mixtures of fatty acids differing in chain length and degree of
unsaturation
 Fatty acid chain is saturated if it does not contain any carbon to carbon double bonds
 Each C atom has two ( atoms attached
 Fatty acid chain is unsaturated if it does not contain any carbon to carbon double
bonds
 Can be monounsaturated only double bond in C chain or polyunsaturated
 Special case of polyunsaturated fatty acids is omega fatty acid
 (as certain number of carbon atoms between terminal methyl group and the last
double bond
 Chemical reactivity of unsaturated fatty acids is determined by position and number of
double bonds
 (igher degree of unsaturation, greater the reactivity provided double bonds
occur in series w/ single bonds in between conjugated double bonds
 )f double bonds are separated by methylene unit greater reactivity results as in
omega fatty acids
o Cis and trans fats
 Unsaturated fatty acids come in two configurations defined by their structure at the
double bonds
 Cis configuration: hydrogen atoms bonding to the C=C are located on the same
side of the double bond
 Trans configuration: hydrogen atoms attached to carbon atoms of double bond
are opposite each other
o Unsaturated fatty acid double bonds exist in foods in the cis rather than trans
configuration
o Melting point
 Temperature at which a solid is converted into a liquid
 Fatty acids exhibit unique melting points and a pure substance such as a single type of
fatty acid will exhibit a sharp melting point corresponding to a defined temperature
 Determines whether a fat will be a liquid, a solid, plastic or brittle at room
temperature
 Melting point is determined by many factors including:
 Fatty acid chain length and degree of unsaturation
 Short chain fatty acids show lower melting points than long chain
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

o
o
o
o
Saturated fatty acids have higher melting points than unsaturated ones
Mixed fat triglyceride is heated melting is gradual over a range of temperatures
rather than one distinct measurable value –showing impure fatty acid
composition
Flavour compounds
 When fat is removed from product formulations, much flavour is removed as well
 )nteraction of fats or oils w/ other atoms creates chemical products that impact food
flavour
 Reversion flavour: mild off‐flavour developed by refined oils that have become
exposed to oxygen
Polar lipids
 Found in membrane of plant and animal tissue
 (ave a degree of water solubility owing to the presence of polar atoms in their
structure
 Glycerophospholipids –important examples of polar lipids
 Structure of such a lipid shows why it is both fat and water soluble
 b/c of ampihilic structure, polar lipids can function in foods as emulsifiers
Pigments
 Variety of natural pigment molecules are lipids associated w/ food lipid matter
 May occur as esters of fatty acids or as crystal forms in liquid oil
 Classes of pigments include carotenoids
 Waxes
 Esters of fatty acids and even numbered long carbon chain alcohols
 Occur in nature as low melting point solids that coast plant leaves and fruits
 )n food industry, waxes are used as protective coatings in some fruits and
vegetables to increase shelf life and flavour quality
Chemical Reactions of Lipids
 Fractionation
 Splits an oil into its higher melting point components and lower melting point
components such as oleic acid
 Crystallization is accomplished so that the crystal portion can be separated from
the liquid portion
 (ydrogenation
 Forced addition of hydrogen atoms to the unsaturated bonds in an unsaturated
fat
o Raises fats melting point and is used in the food industry to harden liquid oils
into semisolid fats
o Fatty acids containing the most double bonds hydrogenate more quickly than
the less saturated ones
 Raising saturated fat level allows process to be controlled
 Results in change of percentage of cis unsaturated fatty acids to trans
unsaturated fatty acids
o (ydrogenation decreases tendency of a fat to oxidise since less unsaturation
means less potential for chemical oxidation to occur
 (ydrolysis
 Reaction requiring heat plus addition of water molecules to separate fatty acids
from glycerol portion of a lipid molecule
o Glycerol can be further changed into a substance called acrolein
o (ydrolytic rancidity: results when stored fats become rancid by the hydrolysis
reaction with water
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

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For each molecule of water that combines w/ fat molecule, one free fatty
acid is liberated
(eat usually causes rancidity to start
Size of liberated fatty acid is important in determining rancidity
Shorter chained fatty acids cause objectionable flavours and odors
associated w. hydrolytic rancidity
)f long chain fatty acids are liberated they do not contribute to off flavour
and odors
)nteresterification
 Removal of fatty acids from glycerol and their subsequent rearrangement or
recombination into numerous configurations which differ from original fat molecule
 Since pure triglycerides contain identical fatty acids )nteresterification
products of diff pure fatty acids are easy to predict in terms of fatty acid files
and proportions of each resulting triglyceride

configurations of fatty acids w/ glycerol are possible account for . % of
/ of the total
o Oxidation
 )n oxidation of food lipids, oxygen reacts with double bonds of unsaturated fatty acids
 Chemical result is production of small organic compounds which generate
undesirable rancid odors in foods that contain oxidized fats or oils
 Original fatty acids + nutritional value are lost
 Unsaturated fatty acid that reacts w/ oxygen forms a hydroperoxide and a chain
reaction results
 (ydroperoxide decomposes further to yield the odorous aldehydes, ketones,
acids and alcohols which cause rancidity
 Quantitiy of hydroperoxide in a fat sample can be measured and is called the
peroxide value PV
 Predicts level of oxidation in fat
o Lipoxidation: describes chemical mechanism in which heat, light, or metals
trigger a chain reaction within stored fats and oils that results in a fat becoming
rancid
 Sequence of steps: initiation, propagation and termination
o Antioxidants are effective b/c they donate hydrogen atoms to the lipid fatty
acid radicals which regenerate original fat molecules from lipid radicals
stopping chain rxn
o Polymerization
 Occurs at the smoke point of a fat temperature at which overheating of a fat causes it
to give off smoke
 The functional properties of lipids
 Aeration –in the production of baked goods that require a creaming step, fat as a
plastic shortening is mixed w/ sugar
 During mixing, air bubbles are incorporated into batter physically held
by crystal molecule arrangements in the fat
 Aerated batter is needed for product to expand during baking to a
desirable volume and height
 Air bubbles become nuclei for gas expansion during heating causing
steam to migrate to neighbouring air bubbles
 Steam and leavening gases expand during baking due to pressure causing
bubbles to expand
 Crystallization
 Food fats regardless of state contain very small solid fat crystals
o
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Crystals are composed of the fat s triglycerides
Polymorphism: fat molecules pack into crystal lattice structures in a
variety of different ways
 Three predominant crystal forms are designated alpha beta and beta
prime having a unique packaging organization –given fat ca exist in one
or more of these forms at a time
 Emulsification
 (omogenous dispersions of an oil and water phase
 Flavour
 Special category of compounds called terpends includes a variety of lipid flavour
molecules from plants called terpenoids
o Can be isolated into essential oil portions by steam distillation
 (eat transfer
 Frying fats transfer heat energy from heat source to surface of the frying food
which is immersed/in contact with the fat
 As food makes contact with hot frying oil moisture in product escapes and is
evaporated off as a steam into the atmosphere
 Portion of hot frying oil is absorbed by the food during frying as moisture leaves
promoting heat transfer inwards
 Mouthfeel
 Fat is a lubricant in the mouth helps to clear particles of food from the teeth
tongue and gums during chewing
 When fat is replaced in a food by a carbohydrate or protein based
ingredient, texture and mouthfeel of resulting low fat food can be altered
 Plasticity
 Refers to the physical property of a fat that describes its softness at a given
temperature
 A plastic fat will respond to an external force by deforming as when squeezed or
spread but holds its shape on a flat surface
 Rapid cooling of a melted fat results in a waxy solid made up of alpha
crystals
 Crystals are unstable and change into clusters of needle like beta prime
crystals, which is the preferred form for plastic shortenings
 Crystal form will convert to stable beta crystals through improper
tempering which means that during manufacture the product did
not form to the correct crystal type b/c it was not held at the proper
temperature for the prescribed time
 Tenderization
 Fats act as a tenderizer in foods
o Dramatic difference in tendernees between a cooked lean cut of meat and one
that is marbled with fat illustrates this
o Presence of fat in baked goods is important to structure
5.3 Food Proteins


o
o
o
o
Proteins are polymers of amino acids and are referred to as polypeptides
Composed of chains of amino acids joined by a peptide bond
Amine group + acid group and a central C atom bonded to ( and to a side chain R
As polypeptides, proteins can be nonconjugated or conjugated
o Most exist as nonconjugated –not bound to other substances and contain only amino
acids
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Conjugated proteins are proteins combined with nonproteins substances such as
carbohydrates and lipids into complex molecules
The Structure of Proteins
o
specific levels of protein structure have been identified
 Primary: linear sequence of amino acids in order within a polypeptide
 Secondary: refers to whether the amino acids together assume either an alpha
helix or beta sheet configuration within a polypeptide
 Tertiary: overall D shape achieved by the folding of the entire protein
molecule –stabilized by bonds such as hydrogen and disulfide between amino
acids that are close to each other due to folded situation of tertiary structure
 Quaternary: protein contains more than one polypeptide chain in its structure
o Denaturation: unfolding of such structure usually due to acid or heat
 Proteins functional properties are altered or lost
o Food proteins are spherical like a ball or elongated like a twisted rope
 Globular proteins: those that are soluble in water
 Fibrous proteins: generally insoluble
The Chemical Reactions and Functional Properties of Proteins
o Proteins in foods are responsible for colors, flavours and textures
o Can function as buffers, emulsifiers enzymes and fat replacers
o Can form gels/foams under proper conditions
Buffering
o Preventing a p( change by undergoing ionization reaction
o Buffering ability of proteins is a function of the amino acids that make the protein
structure
 Carboxyl group behave as acids, and amino groups behave as bases
 Degree of acidity affects food quality and depends on the ph of the medium
surrounding the food protein
o At a certain p( the total number of + charges exceeds the total number of – charges on
the surface of the protein molecule
 )n this acid p( range, net charge on protein is positive allowing it to dissolve
in water
o At a certain p( the total number of ‐ charges exceeds the total number of + charges on
the surface of the protein molecule
 )n this basic p( range, the net charge on the protein would be negative
allowing it to be polar and soluble in water
Denaturation
o Occurs as an unfolding of protein structure without disrupting protein covalent bonds
o Original properties will change
o Thermal processing denatures meat proteins
o Can be thought of as relaxation of protein tertiary structure with decreased solubility
and altered functional properties
o Coagulation is the precipitation of proteins as individual molecules aggregate
Emulsification
o Proteins can stabilize emulsions by acting at oil water interface
o Protein molecules contain both hydrophilic and hydrophobic characteristics and can
situation in between the two phases to stabilize them
 This property is an important function in formation of common food products
ex sausages
Enzymes
o Protein molecules that function to speed up chemical reactions without being used up
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Produce products in the food industry that range from modified starches to protein
hydrolysates
o Modified polymer substrates offer enhanced functionalities in many cases
o Temperature, p( and moisture affect enzyme activity
o Optimum temperature for enzyme function is between ‐ degrees C
 Below degrees enzyme activities slow down and above
degrees proteins
denature
o Dehydration of foods keeps enzymes and substrates apart reducing enzyme activity
Fat Reduction
o Controlled thermal denaturation of whey protein results in a functional protein with
fat like properties
 Applications include dairy products, frosting etc.
Foaming
o Colloidal dispersions of a gas in liquid
o Proteins good foaming agents include eggs, milk and soy proteins
Gelation
o Proteins can form a well‐ordered gel matrix by balancing protein‐protein and protein‐
solvent interactions in food products
o Gel matrices can hold water and other food ingredients to produce various food
products ex. tofu and yogurt
(ydrolysis
o Protein + water + protease enzymes produce amino acids
o Nonenzymatic hydrolysis is breaking apart of molecules due to heat/p(
Solubility
o (ighly soluble proteins are required to produce whipped products, protein films and
emulsions
o Affected by p( and temperature
Water‐(olding Capacity
o W(C water holding capacity of a protein is for example meat can retain water
during application of external forces such as cutting, heating, and grinding
o When – and + charges equal each other protein: protein interactions are at a
maximum
 When protein is not electrically neutral, interactions lessen, allowing for
greater water:protein associations
 )ncreasing salt concentration allows for more Na+ and Cl‐ ions to bind
to the charged groups on protein fibre molecules
o Reduces protein fiber associations with each other in favor of
increased protein fibre:water associations
 As temperature increase, water binding increases in proteins that
form thermally induced gels b/c gelation traps water inside a D gel
network and creates gel surface binding of water molecules
Challenge!
o Milk Protein Chemistry
 )mportant milk proteins are caseins and whey proteins
 Caseins make up % of all milk proteins and whey about %
 As ‐casein, beta‐ casein, k‐ casein, and y‐ casein are the major casein proteins
 Gamma fraction derives from proteolytic enzyme breakdown in milk
of beta casein
 Each fraction exhibits chemical differences
 Alpha‐S contains special structures called phosphoserine units, beta has
and kappa has phosphoserine unit
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o
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o Caseins are important because of their structure, charge and functional properties
Caseins and isoelectric p(
o )soelectric point: crucial p( for all proteins in solution occurs when number of (+
ions equals number of O(‐ ions
 Net charge on protein is
 At isoelectric p(, protein molecule is unstable and is at its most insoluble state
 Causes protein molecules to form ( bonds w/ each other in solution
producing protein clumps and precipitates that separate from water
Casein Micelles
o Caseins exist within micelles each containing thousands of casein polypeptide
molecules
 Casein micelles are large colloidal particles composed of calcium phosphate
complexed to casein
 With each micelle are aggregates of submicelles composed of alpha, beta and
kappa casein polypeptides
 All casein fractions react w/ calcium and become precipitated except
kappa
 Calcium and phosphate complex with the alpha and beta caseins while
kappa casein stabilizes the colloidal casein particles by surface binding
to water
 Phosphate groups of alpha and beta casein but not kappa, react w/ Ca and P to
form crosslink s between submicelles or to form chains )n which phosphate
and citrate link together w Ca
 Kappa‐casein can aggregate within each submicelle so that it is hydrophyillic
yet noncalcium binding, ends form a cap where no cross linking occurs
 Results in kappa form dominating micelle surface
 Casein micelles are stable in milk as colloids unless rennin enzyme is applied
or shift in p( down toward the p) is created
 To make cheese from milk casein micelles must be destabilized
 Enzyme rennin catalyzes splitting of kappa casein into micelle
remnant para‐k‐casein which is hydrophobic
 K‐casein macropeptide is lot to the whey liquid
 )n the presence of calcium, para‐k‐casein becomes insoluble –thus
destabilized, casein micelle remnants aggregate to form a gel –the
cheese curd
Information that you are required to know from chapter 3 –Fat replacers (pg 79‐82)
o Fat content of foods can be reduced by decreasing the amount of fat present or
through addition of water to the product
o Fluid dairy products, reduced fat cheese and baked chips are an example to this
approach
o Food manufacturers achieve fat reduction through use of fat replacer ingredients
 )nclude: carbohydrate based fat replacers, protein based fat replacers and fat
based fat replacers
o Carbohydrate based fat replacers
 )ngredients are plant polysaccharides
 Thicken foods and add bulk providing a mouthfeel similar to that fat
 Cannot be used for frying but can withstand heat and can be used in mat
products ex. dextrins, fibres, gels
 Derived from natural plant products and are considered safe for human
consumption
o Protein‐based fat replacers
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Protein can be blended with gums to form gels
Provide structure and functionality similar to that of fat
Proteins of low molecular weight may act like fats to alter the texture of
products like cheese
 Microparticulation is a food processing method that reduces particular size of
a substance
 Most protein based replacers cannot be used at high temperatures because
protein coagulates and loses its functionality
 b/c protein fat replacers are derived from food proteins, they are safe for
human consumption
o Fat‐based fat replacers
 Contain the same fatty acids formed in regular food fats and can mimic their
characteristics of flavour, baking and shelf life
 Produced by creating fat molecules that have a shorter fatty acid chain length
meaning fewer carbon atoms in the structure
 Modifying the fatty acid composition of triglycerides in this way results in
calorie reduction
 Olestra is a synthetic fat molecule that contains , or faty acids
 Fatty acids are attached to sucrose
 )nhibits working of digestive enzymes with the result that olestra
passes from the body without being absorbed or contributing to
calories
 Stable at high temperatures and can be used in cooking and frying
o The place of fat replacers in the diet
 Food formulated with fat replacers contribute far fewer fat grams and calories
to the diet
 Fat replacers are often incorporated into foods that re not good sources of
other nutrients such as snack foods
Course Manual –Chemistry of Foods (Part 1)
Introduction to Food Chemistry
o Macrocomponents comprise a large proportion of food mass
o Microcomponents comprise a smaller proportion of mass but are vital contributors to
functional or nutritional properties
What is a micro component?
o Blanket term used to describe components in food that comprise a smaller proportion
of total mass
 Many functional and nutritional properties are highly dependent upon their
presence in the product
 Some include:
 Vitamins and minerals
 Antioxidants
 Enzymes
 Organic acids
 Flavourings
 Emulsifiers
 Pigments
 Food additives
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o
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Part :
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Chapter 5 (pg 120‐153) + Challenge and Fat Replacers (pg 79‐82)
Chapter 5 (120‐153): Food Chemistry II: Carbohydrates, Lipids, Proteins
. Food Carbohydrates
The Structures of Sugars
‐ note: for chapter , carb refers to carbohydrate for short
‐ all carbs contain carbon, hydrogen, and oxygen
‐ carbs are classified by the number of sugar units they possess
‐ the basic building block of carbs are simple sugars also termed organic alcohols
‐ ie fructose fruit sugar and glucose: a single carb unit called a monosaccharide
‐ when there are two simple sugars in a carb, it s called a disaccharide
‐ ie sucrose table sugar and lactose milk sugar
‐ other combinations of simple sugars bonded form oligosaccharides and polysaccharides
Monosaccharides
‐ note: monosaccharides will now be referred to as mono for short
‐ mono with carbons are called trioses, = pentoses, = hexoses
‐ important mono s in food are hexoses including glucose, fructose and galactose
‐ these share the same chemical formula C ( O see Fig. 5.1
‐ but there are slight differences in the location of the functional groups
which causes differences in functional properties, like sweetness and
solubility
‐ ie fructose ‐member ring is sweeter and more soluble than
glucose ‐member ring
‐ glucose is the most common mono in food sometimes called dextrose
‐ it is considered to be an aldose due to carbonyl group ‐C=O at carbon being in the
form of an aldehyde
‐ fructose = ketose, since carbonyl group at carbon is in form of keton
‐ galactose occurs in the disaccharide lactose
‐ mono s exist in two forms: straight chain Fischer projection molecules or cyclic
(aworth projection form
‐ in solution, mono s are mostly in ring form since the functional groups are
carbon alcohol group ie ‐O( and carbon aldehyde group undergo
interamolecular cyclization, which is a reaction that joins C and C to form a closed
ring
‐ ring formation eliminates the carbonyl group and leaves an O( group
Disaccharides
‐ two mono s with a glycosidic bond form disaccharides
‐ there are important disaccharides in food: sucrose, lactose, maltose
‐ sucrose: fructose and glucose are linked between aldehyde group of C of glucose
and ketone group of C of fructose
‐ it is used in crystalline form
‐ lactose glucose and galactose is found in milk and dairy products
‐ maltose = glucose
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The Functional Properties of Sugars
‐ sugars contain important reactive, functional groups: the –C=O carbonyl group and the –O(
alcohol group
‐ alcohol group is important for sweetness and solubility
‐ found in various locations in molecule ie glucose has
‐ alcohol groups readily form hydrogen bonds with water, making it very soluble
‐ molecular size and weight affect sugar molecule s affinity for water, as well as
crystalline behavior lattice form of solid sugars
‐ carbonyl group is important for reducing activity and the Maillard browning reaction, which
can cause colour and flavor changes
Reducing Sugars
‐ reducing sugars contain the aldehyde or ketone carbonyl group
‐ they react with other substances through redox chemistry to produce a reduced
substance plus the oxidized sugar molecule; therefore, they re reducing agents
‐ all mono s and some disaccharides are
‐ dextrose equivalent DE related to solubility, reducing action, viscosity, etc.
‐ it s a measure of % of glycosidic bonds hydrolyzed in disaccharides and
polysaccharides, indicating the level of reducing sugar present
‐ pure dextrose has DE of
, compared to for starch glucose polymer
‐ higher DE means higher solubility and reducing ability of sugar
Browning
‐ important browning reactions in sugars: Maillard browning and caramelization
‐ Maillard browning: reducing sugars reactivity: pen>hex react with amino acids
‐ result of Maillard reaction, brown pigments called melanoidins
‐ can cause unwanted browning, and wanted aromas
‐ nonenzymatic browning
‐ reaction steps:
‐ condensation: a reducing sugar with a free carbonyl group C=O
reacts with an amino group to produce glycosylamine
‐ Rearrangement: glycoslamine reacts to Amadori compounds
colourless to pyrazines furfurals: member ether rings
‐ colour and flavour begins to develop at this stage
‐ Polymerization: colourless intermediate compounds to brown
melanoidins
‐ Camelization: brown caramel pigments from heating sugars to
^C
‐ Caramelen C ( O is a pigment that undergoes fragmentation and
dehydration to form acids that impart flavours
‐ caramel
‐ colouring refers to colour additive
‐ caramels refers to sauces/candies from camamelize carbs
Crystallization
‐ sugars exists in syrup and crystalline state crystallization
‐ crystallization depends on moisture, temp, and conc of sugar in food system
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‐ crystal: solid made up of units in a repeating pattern
‐ two stages of crystallization
‐ transfer of sugar molecule to the surface of a crystal
‐ incorporations of sugar into crystalline structure
‐ graining: when sugar crystals reform in solution ie milk lactose
‐ desired in hard candies
Humectancy
‐ humectant: a substance that has an affinity for moisture
‐ sugars can influence the state of water in food systems
‐ they hydrogen bond with water molecules, making water less avail for microbes
‐ therefore, sugars can preserve food somewhat
‐ conversely, if you want something free‐floating, a course sugar like sucrose is good
Inversion
‐ hydrolysis of sucrose to mono s makes a sweeter product
‐ the mixture of the two mono s produced are called invert sugar
‐ utilizes the enzyme invertase
Oxidation and Reduction *Recall oxidation occurs to sugars that are reducing agents
‐ oxidation of the R‐CO( aldehyde group in sugars causes loss of sweetness
‐ converts the aldehyde to an acid (O‐C=O group
‐ example
‐ glucose R‐CO( + oxygen  glucuronic acid R‐COO(
‐ reduction of the carbonyl group ‐C=O of reducing sugars forms sugar alcohol
‐ examples: sorbitol, mannitol, maltitol are moderately sweet sugar alternatives
‐ sugar + hydrogen glucose, fructose, maltose
Sweetness and Texturizing
‐ sugars differ in sweetness; some are better sweeteners than others
‐ sugars also affect texture by determining water availability
‐ hydrogen bonds with water to their O( groups
‐ starch gelatinization can be delayed due to sugars
‐ reduced the viscosity and gel strength of starch ie puddings
‐ sugar tenderizer: in cakes, the right amount of sugar creates soft, full volume
Polysaccharides and Their Functional Properties
‐ complex due to size of structures carbs:
‐ oligosaccharides:
or fewer sugar units
‐ ie raffinose and stachyose in dried beans, soybeans, etc.
‐ polysaccharides: at least
or more sugar units
‐ ie starches amylase and amylopectin
‐ important in food: beta‐glucans, cellulose, dextrins, fructooligosaccharides,
maltodectins, pectic substances, starch, vegetable gums
‐ they have reducing and non‐reducing ends which are susceptible to enzymes
‐ sugars exist in two structural forms differing on orientation of O( on first carbon:
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‐ alpha: projects downward
‐ beta: projects upward
‐ the orientation of the O( also affects the alpha/beta nature of the glycosidic bond that
join two mono s
‐ see Table . on pg.
Beta‐glucans
‐ these are polysaccharides of glucose that are similar to cellulose but less linear
‐ in grains like oats, barley, and yeast
‐ they lower cholesterol and activate macrophage cells on immune system
‐ water‐soluble form of oat flour can be used as soluble fiber Oatrim
‐ can be used as a fat replacer and texturizing agent with reduced calories
‐ for fiber, see Table .
Cellulose
‐ most abundant carb polymer
‐ from plant cell walls > impossible to digest for humans
‐ composed of glucose linked by beta‐ , glycosidic bonds
‐ can be used as a fat replacer > similar mouthfeel and flow properties
Dextrins and Maltodextrins
‐ dextrins: composed of linear arrays of glucose linked by beta‐ , glycosidic bonds made by
hydrolyzing the amylase portion of starch dextrinization to make pyrodextrins
‐ can be used as less carloric fat replacers
‐ not to be confused with dextrans: alpha‐ , bonding instead and from bacteria/yeast
‐ they are considered to be a food gum
‐ maltodextrins: polysaccharide fragments from starch hydrolysis
‐ ie made from corn starch to get a low degree of polymerization DP
‐ when processed they become gels or powders
‐ can be used as fat replacers, texture modifier, or bulking agent
‐ they have a dextrose equivalent DE of less than
‐ the lower the DE, the less sweet the carb
‐ DE s of
and above, the carb is classified as corn syrup
‐ corn syrup solids are corn syrups dried to a crystalline form
Fructooligosaccharides (FOS)
‐ FOS are naturally occurring sugars: multiple sucrose attached to to fructose
‐ they are known as prebiotics, which promote the growth of probiotics bacterial
organisms beneficial to health
‐ many benefits to FOS
Inulin: Dietary Fiber
‐ inulin: a FOS that functions as a soluble dietary fiber
‐ occurs naturally ie onion, asparagus, etc.
‐ made of fructose units with a terminal glucose chain length
‐ beta‐ , fructan
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‐ Gfn: where G is the glucosyl unit, f is fructose, and n is the # of units linked
‐ it is not digestable but fermentation adds . kcal/g
‐ in food, it forms viscous solutions at low conc
‐ at higher conc > gel‐like substance
‐ therefore, it can be a fat and sugar replacer to simulate creamy mouthfeel via texture
modification
‐ can also be used to create a water‐in‐oil emusion where inulin binds to water and stabilizes
the emulsion while providing creamy mouthfeel
‐ also a fiber and bulking agent
Pectic Substances
‐ they are high molecular weight polysaccharides from plant cell wall middle lamellae
‐ made of galacturonic acid chains > methylated carboxylic group during fruit ripening
‐ degree of esterification DE : proportion of methyl esters in pectic substance
‐ protopectin: nonmethylated galacturonic acid polymers in immature fruit
‐ pectinic acid: methylated > during ripening
‐ pectic acid: a short‐chain demethylated derivative of pectinic acid > overripe fruit
‐ in solution, pectin molecules are hydrated hydrogen bonding and ion dipoles
‐ Gelation of pectin is possible, depending on lower/high methoxyl
‐ LM pectin has less than % of the carboxylic acids esterfied with methanol
‐ (M pectin: more than % of the carboxylic acids are esterfied
‐ (M is the only one found naturally in fruits
Pectin/Gelation
Starch
‐ pectins are able to form colloidal dispersions, sols and gels
‐ pectin gels: system with lots of water in D solid network
‐ solute:solvent interaction between water and carboxylic COO( and alcohol
O( groups
‐ see figure . for a comparison of LM and (M pectin gel formation
‐ LM requires calcium to form gel
‐ (M requires sugar and acid
‐ both need pectin:pectin interactions which are prevented by water
‐ a polysaccharide from plants such as corn, potatoes, rice, and wheat
‐ polymer of
or more glucose units
‐ branched amylopectin and unbranched amylase regions
‐ ratio is important in processing
‐ starch polymers occur in a state of granules in plants
‐ modified starches function to in film formation, freeze‐thaw tolerance, pasting and
gelling, enhanced solubility, and promote viscosity
‐ ie pregelatinized starch for product thickness
‐ starch gelatinization: heated starch granules absorb water and swell irreversibly
‐ increase in entropy, starch crystallites melt and become soluble
‐ starch pasting and gel formation
‐ starch paste: a starch‐water system with viscous and elastic properties
‐ follows the gelatinization process
‐ involves swelling, exudation, and disruption
‐ at this stage, most granules have gelatinized > increases visocity
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‐ gelation after gelantinization and pasting
‐ formation of gel from the cooled paste
‐ easier with starches of high amylase content
‐ amylopectin starches make gummy textures thickening agent
‐ starch gel: rigid, thickened starch‐water mix with solid properties
‐ starch retrogradation
‐ when the broken down granule structure reassociate, a decrease in entropy
‐ due to intermolecular hydrogen bonding, esp between amylose
‐ gel texture stiffens to rubbery one over time
‐ syneresis: loss of water from gel > not freeze‐thaw stable
‐ see Figure .
Vegetable Gums
‐ these are plant hydocolloids – distribute in water as colloidal dispersions
‐ long chain polymers of hexoses and pentoses
‐ branched vs linear polymers
‐ they are virtually non‐caloric since used at low levels > fat replacer
‐ they have high solubility, p( stability, and gelling ability
‐ they provide food with smooth texture, thickeners, and water binders
‐ can also behave as emulsifiers and increase viscosity
. Food Lipids
Structures and Types of Lipids
‐ organic, nonpolar, hydrophobic
Fats and Oils
‐ known as triacylglycerols: trimesters of glycerol and fatty acids Fig .
‐ glycerol: C molecule with three alcohol groups
‐ fatty acids is a chain of carbons plus an acid COO( group and methyl group
‐ ester bonds join the O( of glycerol and COO( of fatty acids lose water
Saturated and unsaturated fats
‐ saturated: no double bonds, each carbon is saturated with hydrogen
‐ unsat: one mono or more poly double bonds lower # of hydrogen
‐ omega fatty acid: certain number of carbons between terminal methyl group and
the last double bond, which is the one furthest from COO( end see section .
‐ number and position of double bonds determines reactivity
‐ higher with more double bonds/unsaturation
‐ conjugated double bonds: double bonds separated by single bond
‐ even higher reactivity with methylene interrupter pattern
Cis and trans fat
‐ cis more common in food : kink formed by hydrogen bonds on same side of
double bond
‐ trans: hydrogens on either side of the double bond
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Melting point (MP)
‐ MP is higher for saturated fats than unsat
‐ trans configuration is higher than cis
‐ therefore, tran and saturated fats are similar hard at room temp
‐ longer fatty acid chains have a higher melting point
Flavour Compounds
‐ reversion flavour: mild off‐flavour of refined oils exposed to oxygen
‐ lessen product
Polar Lipids
‐ these have some water solubility some hydrophilic components
‐ glycerophospholipids see Figure .
‐ amphiphilic structure
‐ can act as emulsifiers
Pigments
‐ esters of fatty acid or crystal forms in an oil
‐ ie carotenoids beta‐carotene
Waxes
‐ esters of fatty acid, even‐numbers long carbon chain alcohols
‐ natural low melting point solids on plant leaves and fruits ie beeswax
‐ used to increase shelf life > keep moisture in/out
‐ carnauba wax: from palm trees > in chewing gum coating
Chemical Reactions of Lipids
‐ hydrogenation, hydrolysis, interesterification, oxidation
Fractionation
‐ splits an oil into higher and lower melting point components
‐ crystallization allows each part to be separated
Hydrogenation
‐ force hydrogens to bond in unsaturated fat
‐ raises melting point > can produce trans fats
‐ decreases the tendency of a fat > less unsaturation = less oxidation potential
Hydrolysis
‐ requires heat plus addition of water to separate fatty acids from glycerol
‐ can produce acrolein
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‐ hydrolytic rancidity: when stored fat become rancid by hydrolysis with water
‐ via heat or lipase
‐ the shorter the chain, the greater the rancidity eg butter out too long
Interesterification
‐ removal of fatty acids from glycerol and their rearrangement into numerous
configurations, different from the original molecule
‐ results in mixture of fatty acids > can offering improved creaming
Oxidation
‐ oxygen reacts with double bonds of unsaturated fatty acids
‐ causes rancidity
‐ hydroperoxide: the fatty acid that reacts with oxygen forms this
‐ decomposes to cause rancidity
‐ measured as peroxide value PV > oxygen level in fat
‐ lipoxidation: when stored fat goes rancid via heat, light, or metals
‐ steps: initiation, propagations, and termination Fig .
‐ antioxidants in storage are helpful
Polymerization
‐ after hydrolysis, fatty acids can form polymers
‐ can increase viscosity of oils
‐ occurs at the smoke point: temp at which overheating causes smoke
The Functional Properties of Lipids
‐ flavour, texture, fullness factor of food, structure/stability, emulsion, tenderness, aeration, colour,
mouthfeel, heat transfer
Aeration
‐ fat is a plastic shortening mixed with sugar
‐ in batter ie cakes , air allows expansion
Crystallization
‐ polymorphism: the way fat crystals pack together
‐ alpha, beta, and beta prime forms
‐ temp changes result in change of state and crystal form
‐ solid fat index: ratio to solid to liquid fat
Emulsification
‐ emulsions are homogeneous dispersions of an oil and a water phase
‐ ie emulsion in batter to help create the air bubbles
Flavour
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‐ terpenoids: terpenes that impart flavour
Heat Transfer
‐ increases fat content of food as moisture leaves ie frying
Mouthfeel
‐ fat acts as a lubricant in the mouth, helps clear particles from mouth parts
‐ contributes smoothness and texture
‐ fat‐based fat replacers in Table .
Plasticity
‐ refers to the physical property of a fat, softness at room temp
‐ tampering: manufacturing the correct crystal type at proper temp
Tenderization
‐ lean meat is dry and tough to chew, marbled cut is moist, tender, easier to chew
‐ softer crumbs in cake > limits tought gluten protein dough structure
. Food Proteins
‐ proteins/polypeptides are made of amino acids
‐ join acid end to amino end by peptide bonds condensation reaction
‐ see Figure . for common amino acid structure central carbon, amine, acid group, side chain and
how they differ
‐ conjugated ie glycoproteins, lipoproteins, phosphoproteins vs noncongated proteins
The Structure of Proteins
‐ there are four levels of protein structure: primary, secondary, tertiary, quaternary
‐ this describes their shape
‐ primary: linear sequence of amino acids in order in a polypeptide
‐ secondary: alpha vs beta helix
‐ tertiary: D shape after folding the protein hydrogen and disulfide bonding
‐ quaternary: when a protein contains multiple polypeptides linked together
‐ globular vs fibrous proteins
The Chemical Reactions and Functional Properties of Proteins
Buffering
‐ refers to preventing a p( change via ionization
‐ function of carboxylic behave as acids and amino as bases group ionization ability
‐ this ability is called amphoteric
‐ positive when p( is low and negative when p( is high charge on protein
Denaturation
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‐ unfolding of the tertiary D folded structure of a protein, usually by heat or acid
‐ lose of functionality
‐ doesn t disrupt covalent bonds though
‐ ie cooking meat
Emulsification
‐ proteins can stabilize emulsions at the oil‐water interface/boundary
‐ due to their hydro‐philic and ‐phobic components
Enzymes
‐ used to speed up reactions and product a wide variety of food products Table .
‐ temp, p(, moisture affect their ability
Fat Reduction
‐ reduced caloric versions are made from whey/milk/egg protein
‐ can act as fat replacers
Foaming
‐ foams are colloidal dispersions of gas in liquid
‐ ie ice cream, whipped topping, beer froths
Gelation
‐ protein‐protein and protein‐water interactions
‐ can hold a variety of products together
Hydrolysis
‐ protein + water + protease enzymes = amino acids
‐ heat or p( to proteins also = amino acids nonenzymatic
Solubility
‐ protein solubility is affected by temp and p(
Water‐Holding Capacity (WHC)
‐ W(C: retention of water ie meat during cooking
‐ depends on charge of protein, protein‐water interactions increase with charge
‐ temp increases W(C
‐ p(
‐ salt increase W(C
Challenge
Milk Protein Chemistry
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‐ chemistry as it relates to cheese
‐ the important milk proteins are caseins
% and whey proteins
%
‐ lactalbumin, lactoglobulin, immunoglobulins are the major whey proteins
‐ several types of casein proteins
‐ caseins are insoluble at p( . and below but are more resistant to heat
‐ they form gels with rennin added and precipitate in presence of acid
‐ caseins have a disordered tertiary state
‐ whey proteins have a more ordered, globular structure with disulfide links
Casein and Isoelectric pH
‐ isoelectric point/p(: critical p( for proteins in solution
‐ when ( ions = O( ions ie neutral charge on surface of protein
‐ at this point, proteins are unstable and in their insoluble state
‐ therefore, proteins in solution form hydrogen bonds with each other
‐ creates protein clumps and precipitates separate from water
‐ exploited in cheese‐making
‐ ie cheese curds from clumping of casein, isoelectric p( below
Casein Micelles
‐ these are large colloidal particles composed of calcium phosphate complexed to casein
‐ contain lots of polypeptides
‐ all casein fractions react with calcium to become precipitated, except kappa stabilizes the
colloidal casein particles by surface binding to water
‐ refer to Fig. .
‐ casein micelles are stable in milk as colloids
‐ destabilized in milk production: rennin slits stabilizing kappa‐casein
‐ eventually forming a cheese curd
Fat Replacers (79‐82)
‐ for specifics see Table .
‐ fat can simply be reduced or diluted with water
‐ manufactured fat replacers:
‐ carb‐based
‐ plant polysaccharides thicken and add bulk > similar mouthfeel as fat
‐ some are digested, some are not
‐ ie carrageenan, cellulose gels, corn maltodextins, dextrins, fibers, gums, pectin,
starch gels
‐ cannot be used for frying but do withstand heat ie in meat
‐ protein‐based
‐ can be blended with gums to form gels
‐ structure and functionality similar to fat
‐ microparticulation: process that reduces particle size of substance
‐ the products of this give creamy mouthfeel
‐ cannot be used at high temp
‐ fat‐based
‐ mimic regular fat properties
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‐ short chain fatty acids are utilized > reduces calories
‐ Olestra synthetic fat molecule
‐ fatty acids attached to sucrose instead of glucose
‐ inhibits digestive enzymes > no calories
‐ pros vs cons
Unit 4: Chemistry of Foods
C(APTER : FOOD C(EM)STRY ))): COLOUR, FLAVOUR AND TEXTURE
‐
Colour, flavour and texture are three key factors that drive consumer acceptance of foods
‐
Understanding the chemistry of the molecules responsible for colour, flavour and texture as
influenced by temperature, oxygen and various elements and molecules has opened up a field of
functional ingredient applications
. Food Colour Chemistry
‐
Colour can affect the way consumers perceive flavour
‐
)n understanding the chemical basis of food colour, the food technologist can address quality
assurance issued regarding colour stability, important in both processed foods and unprocessed
foods during storage
What is Colour?
‐
Colour describes a perception of a physical attribute of food arising from a collection of
sensations
‐
)t is reflected light that determines the colour of a food
‐
Surface colour of food can be characterized by three qualities
o
(ue which is the actual colour name
o
Saturation or chroma, clarity and purity of the colour
o
)ntensity, the range from lightness to darkness of colour
‐
Surface appearances: shiny, glossy, cloudy, and translucent
Pigment Molecules
‐
Pigment or chromophoretic compounds in food constitute a structurally diverse group and
posses extremely complex chemical and physical properties
‐
Colour compounds can be classified according to chemical structures
‐
Five major groups of natural food pigment
o
Anthocyanins, plants, water‐soluble
o
Betalains, plants, water‐soluble
o
Carotenoids, plants, lipid‐soluble
o
Chlorophylls, plants, lipid‐soluble
o
Myoglobin, animals
‐
)n some fish tissues such as salmon, the bright orange is due to carotenoid pigments
The Colour Chemistry of Red Meat
‐
Myoglobin is a single polypeptide, a globular protein containing the globin protein part and a
prosthetic group called heme
‐
)ron in unoxygenated myoglobin exists int he reduced state, as ferrous Fe + iron
‐
Oxidation and reduction of the iron atom in myoglobin are linked to colour change in meat
‐
When meat obtained from a slaughter house is exposed to air myoglobin s functional property
is to bind to oxygen
‐
After meat is cut and comes into contact with oxygen, the unoxygenated myoglobin s iron
loosely binds oxygen and converts myoglobin to oxymyoglobin, creating a bright red colour
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‐
)f exposure to oxygen continues, oxidation does take place, and production of metmyoglobin
results
‐
Metmyoglobin is associated with aged meat exposed to air and produces a grayish or brown
meat colour
‐
The iron in metmyoglobin changes from the reduced Fe + to the oxidized Fe + state, which
alters the colour
‐
)n nitrate‐cured meats, myglobin reacts with nitric oxide to produce nitric oxide myoglobin,
which is a bright pink‐red
The Colour Chemistry of Fruits and Vegetables
‐
Appealing colour of fruits and vegetables is due to naturally occurring plants pigments that
absorb and reflect light at certain characteristic wavelengths
‐
All plant pigment molecules contain conjugated double bonds
‐
Chlorophylls in addition contain metal‐coordinated porphyrin rings
‐
Colour is a result of resonance within the ring structures in porphyrin rings chlorophyll,
myoglobin, and hemoglobin as well as along conjugated carbon chains
‐
Resonance electrons are spread across the atoms containing alternating single and double
bonds, and their movement across carbon‐to‐carbon bonds gives colour
‐
Plant pigment molecules are classifies into three groups based on structure
o
The phenolic‐based pigments anthocyanins, anthoxanthins, and betalains
o
The carotenoids
o
The chlorophylls
‐
Anthocyanins
o
Are water‐soluble flavonoid compounds that range in colour from deep purple to orange‐red
o
Flavonoids are chemically related phytochemicals and include the anthocyanins and
anthoxanthins
o
Flavinoids contain two phenol rings and an intermediate ring of variable structure
o
Anthocyanin pigment colour if p( sensitive, being red in strong acid, colourless at p( , and
blue at neutral p(
‐
Anthoxanthins
o
Are colourless or white pigments that can become yellow
o
Contribute only slightly to food colour
‐
Betalains
o
Represent a group of two types of water‐soluble plant pigments:
§
Betacyanins which encompass about
violet‐red pigments
§
Betaxanthins, a series of about
yellow pigments
‐
Carotenoids
o
Are a class of fat‐soluble plant pigments that consists of carotenes and xanthophylls
o
Carotenes are hydrocarbons
o
Xanthophylls are oxygenated carotenoids containing alcohol, carbonyl or other functional
groups
o
Contribute red, orange, and yellow as a result of resonance in isoprene units within the overall
carotenoid structure
‐
Chlorophylls
o
Are green lipid‐soluble plant pigments that contain a porphyrin ring complexed to magnesium
o
Plants contain two naturally occurring chlorophyll tpes: chlorophyll a and chlorophyll b
o
Vegetables may contain a number of chlorophyll a and b derivatives because of changes to the
molecules during thermal processing or exposure to extreme p( environments
§
Such situations can alter their colour
o
An enzyme called chlorophyllase catalyzes the degradation of chlorophyll
o
The canning of green vegetables using low heat results in loss of bright green colour and a
change to dull olive green due to production of pheophytin
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The Colour Chemistry of Food Colorants
‐
A colorant is a pigment used to impart colour to a food or beverage
‐
Colorants were from two distinct categories of substances: natural colorants or those naturally
derived, such as annatto extract and synthetic artificial colorants
‐
FD&C colorants
o
The FDA today does not recognize any colorants as natural
o
For regulatory purposes all colour ingredients are additives
o
Two categories of food colorants today are: those certified as FD&C colorants and those that
are exempt from certification
o
The structures of the FD&C colorants contain phenolic rings having double bonds and various
functional groups
‐
Food colour suppliers manufacture what are called dyes and lakes
‐
Dyes are water‐soluble chemicals that are used to colour entire food products, for example
lollipops, throughout
‐
A lake is an insoluble powder formed by precipitation of a water‐soluble food colorant
Exempt Colorants
‐
These range from annatto to caramel, and from cochineal and grape skin extract to paprika
‐
Cochineal extract: used by Egyptian women to colour their lips, the dried bodies of cochineal
insects are treated with ethanol and a red solution is produced
‐
Caramel colour: dextrose, sucrose, invert sugar, lactose, malt syrup, molasses, and various
starch hydrolysis products can serve as reactant in the production of caramel colour
o
The actual formation of caramel is through the nonenzymatic thermal process known as
caramelization
o
All those products has a glucose content which is ket to producing brown sugar
. Food Flavour Chemistry
‐
Flavour is a property of food material and the receptor mechanisms of the human body
‐
Flavour involves both taste and aroma
‐
The study of flavour includes the composition of food compounds producing taste or odour, and
their interaction with receptors of the taste and smell sensory organs
‐
(umans have four basic tastes sweet, salty, sour and bitter
Chemical Structure and Taste
‐
A first requirement for a substance to produce a taste is that it has to be water soluble
‐
Thus sour, salty, bitter and sweet substances contain hydrophilic functional groups
‐
Astringency and umami are two other areas of taste on the tongue
‐
Astringency is a sensation of puckering in the mouth and is believed to be a result ofb tannis or
polyphenols reacting with proteins
‐
Umami is described as a savory and delicious sensation
‐
Pungency
o
The sensation of spicy heat or chemical heat in the oral cavity is due to specific chemicals
primarily from cruciferous vegetables and chili peppers
o
The sensation, identifiable as a warming or hot sensation in the mouth and lips, is termed
pungency
o
When pungent foods are consumed, endorphins are also released, creating a sensation of
pleasure amidst the pain
o
Capsaicinoids are pungent alkaloid compounds that occur in chiles
o
Scoville organoleptic test was developed to systemize the potency ratings of pungent
substances
o
(PLC is a more reliable way to measure potency ratings
‐
Cooling sensation
o
The opposite sensation to heat is the sensation of coolness in the mouth
o
This effect is familiar to those who chew spearmint or peppermint gum or have experienced
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those flavours in a dessert
o
Key substances responsible for the cooling effect are menthol and isomers of menthol
o
Menthol is a crystalline cyclic alcohol and it is the primary constituent of peppermint oil, which
provides a fresh minty flavour and aroma
o
Polyols are polyhydric alcohol counterparts of the sugars maltose, mannose, sucrose and xylose
o
Sorbitol has been the most frequently used polyol because of its humectant properties
Process and Reaction Flavours
‐
Browning reactions may involve caramelization of sugars or the Maillard reaction between
naturally occurring reducing sugars and amino acids, amines, small peptides, and proteins
o
Responsible for the final flavour of cooked and processed foods
‐
Producing food flavours
o
Not only are food flavorists busy studying the natural flavours present in whole foods, but in
addition, they isolate and develop flavouring ingredients, called flavour compounds or flavour
additives
o
These include artificial flavours, essential oils, extracts, natural flavours, oleoresins, process
flavours and reaction flavours
o
Process flavour substances are substances obtained by heating a mixture of ingredients, not
necessarily themselves having flavour properties, of which at least one contains nitrogen and
another is a reducing sugar
o
Reaction technology can be used to produce what are referred to as reaction flavours
o
Reaction flavours are flavours produced by chemical reactions taking place under controlled
conditions
o
A top note is the predominant initial aroma or flavour characteristic for a substance
‐
Enzyme‐produced flavours
o
A large number of flavour compounds can be produced by enzymology if the right enzyme
system and substrate can be found
o
For meat flavour, a tenderizing enzyme protease is added to meat and the mixture is heated
and held at an optimal temperature for the enzyme to function
o
Once the meat is liquefied, the temperature is raised to kill the enzyme and water is expelled
from the system
o
Enzymology and fermentation are often combined in the production of flavours
o
The enzymes are harvested from bacteria, yeasts, and molds that are grown industrially
o
Different flavours can result when yeasts are grown on corn syrup vs. Whey protein
o
Not only the choice of growth medium, but the strain of yeast, the fermentation conditions, and
the form of processing can affect the flavour obtained from the yeast
o
Autolyzed yeast and autolyzed yeast extracts indicate that the yeasts have been centrifuged to
remove cell wall material in order to concentrate such flavours and flavour precursor substances as
free amino acids, peptides, monosaccharides, and Maillard reaction products generated during
thermal processing
Flavour Enhancers
‐
FDA has proposed that a flavouring is a substance that has a flavour of its own at the level at
which it is used in a food, while flavour enhancers and flavour potentiators do not themselves impart
flavour, but rather intensify in some manner the flavours that are naturally present or are added to
food
‐
Protein (ydrolysates
o
A protein breakdown product obtained via enzyme or chemical action
o
Function in foods as both flavourings and flavour enhancers
o
Enhance food nutritive value, enhance protein functionality and adding flavour
o
Proteins are hydrolyzed in a series of steps to produce proteoses, peptones, peptides, and
amino acids, which differ in size and molecular weight
o
(ydrolyzed vegetable proteins are derived from soybeans and are used for flavour, and as
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alternate sources of protein to meat dairy products
‐
Flavour encapsulation
o
A technique applied to flavours to accomplish convenience, stability and times release
o
Flavours, as well as vitamins, and other substances, have been successfully encapsulated with
specially designed fat systems that coat the encapsulated material
o
This approach offers advantage for certain baked foods, extruded foods, fried foods, and
processed meats
o
Encapsulation technology protects flavours in a variety of potentially destructive ways: thermal
processing conditions, storage conditions, and consumer conditions
The Chemistry of Flavour Deterioration
‐
Off‐flavours, sometimes confused with taints , refer to an unwanted flavour development in
foods
‐
A taint results from external contamination from the environment, whereas off‐flavour results
from internal chemical changes in foods during processing or storage
‐
One type of off‐flavour that can result in dairy products is a fishy flavour which results from the
formation of trimethylamines by the hydrolysis and oxidation of lecithin, a naturally occurring
phospholipid in milk
‐
Lipid food material is subject to two ways of chemical reactions that lead to rancidity
‐
(ydrolytic rancidity reactions produce off‐flavours due to liberation of free fatty acids by water
hydrolysis and enzyme action
o
(eat acts as a catalyst for this reaction, and lipase enzymes can as well
‐
Oxidative rancidity involves reactions between unsaturated fatty acids and oxygen, producing
hydroperoxides
‐
The breakdown of hydroperoxides results in small molecular weight compounds like acids,
alcohols, aldehydes and ketones
‐
Cooked meat that is refrigerated and later reheated is subject to a type of oxidative rancidity
called warmed‐over flavour
o
)t is an unpleasant, stale taste in re‐heated meats
o
)n this reaction iron acts as a catalyst
‐
Meats that have high phospholipid content in the fatty portions exhibit warmed‐over flavour
problems
. Food Texture
‐
The texture of a food is a quality parameter of major importance
‐
)t refers to the perception of food structure when a food item is held by the fingers, pushed by
the tongue against the palate, or chewed by the teeth and sensed within the oral cavity
‐
Texture is determined by the microstructure of animal and plant tissue and it is influenced by
the prescence of texturizing ingredients
‐
Mouthfeel and food texture are closely related parameters
‐
Mouthfeel encompasses the entire spectrum of a food s physiochemical characteristics inside
the mouth, from the initial sensation inside the oral cavity to the first bite, through chewing and the
act of swallowing
‐
Food texture changes as it is chewed, as structures are broken dow and moisture is released
Texture Classification
‐
Objective texture measurement refers to the use of analytical equipment to determine: food
microstructure and macrostructure, resistance to a cutting force that causes shear, or an applied
force that causes deformation and/or flow behaviour
‐
Rheology is the study of the flow of matter in response to force
‐
The rheological behaviour of food tells the food scientists:
o
(ow a fluid food like a beverage, oil, chocolate, sauce, syrup or gravy will pour
o
Steph is the best
o
(ow a fluid will be sensed by the tongue
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o
(ow long it will take for the fluid food to be cleared from the palate
‐
Fluid foods are classified as either Newtonian or non‐Newtonian, depending on their flow
behaviour
The )nfluence of Chemical Forces in Water and Fat Systems on Texture
‐
Texturizing agents can impart body by increasing viscosity, promoting gelation, increasing
firmness through the binding of water or by causing the crosslinking of molecules, or through the
stabilization of emulsions
‐
Water‐based systems
o
Water can exist in foods in one of three situations: as free water, as absorbed water, and as
bound water
o
One key importance to food texture is the presence of water and the manner in which it is
chemically positioned
o
Free water becomes entrapped within a gel as a consequence of gelation
o
Food water activity can be viewed as a predictor of food texture
o
Food texture ranges from hard and crisp, to dry and firm, to soft and moist
‐
Fat‐based systems
o
Cocoa butter is the lipid material from which chocolate is made
o
As a fat it contributes a smooth, creamy consistency, a softness, and a pleasant mouthfeel
o
The consistency of any fat is the result of an organized three‐dimensional network of solid fat
crystals embedded in liquid oil
o
Crystals are composed of specific glycerides
o
The size, shape and stability of the fat crystals affects the conversion of solid fat to liquid oil
The Chemistry of Food Texturizing Agents
‐
Texturizing agents promote viscosity, increase firmness and cause gelation
o
tend to be starches, non starch polysaccharides and proteins
‐
denatured proteins and non‐gelling polysaccharides cannot form string covalent bonds
required for gelation to occur
o
instead they contribute to increased product viscosity
‐
Polysaccharides
o
Can interact with each other in such a way as to enhance gelation
‐
Fat replacers
o
Fat substitutes have same physical properties of fat and replicate fat functions when used in
food
o
Fat mimetics do not possess all the true fat physical properties, such as flavour and flavour
release, but can imitate some of them, such as creaminess
§
Alter texture by controlling water in food systems
§
Typical one is a combo of a polysaccharide and water, produces gelling characteristics that
helps imitate fat in foods
‐
Sugars
o
Sugars compete with protein and starch for water in food systems
§
This reduces the amount of water available for starch gelatinization and for protein and starch
gelation
‐
Collagen and gelatin
o
Gelatin, another texturizing agent, is a soluble protein derived from insoluble collagen present
in animal collective tissue
o
The same chemical forces that stabilize collagen in connective tissue are active in the
stabilization of gelatin gel systems
o
Gelatin is locked within collagen s three‐dimensional structure, only to be liberated when
collagen is subjected to acid, alkaline, or heat treatment
o
free, single tropocollagen strands are considered individual gelatin molecules
o
The gelatin molecules so produced are isolated and concentrated into a powdered ingredient
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o
Upon addition of hot water, the gelatin disperses as random coil polypeptides
o
The water solubilises the gelatin and forms a sol, in which water is the continuous phase and
gelatin, the dispersed
o
Cooling increases the viscosity of the system
o
Eventually, polymer:polymer gelatin associations result in gelation, a three‐dimensional
network of gelatin polymers stabilized by noncovalent bonds at junction zones
o
The use of weak acid additives like lemon juice or vinegar is the traditional method of
overcoming meat toughness
§
These promote swelling of collagen, and this swelling enhances chain dissociation through
breakage of noncovalent bonds, including hydrogen bonds
The Challenge: The Chemistry of Sweeteners and Sweetness
Theory of Sweetness: The Overview
‐
Tongue has traditionally been divided into four taste zones, which accomadate roughly
taste receptors for the primary tastes, including sweeteness
‐
)t has been proposed that food molecules responsible for these tastes can bind in some way to
specific protein receptor molecules on the tongue for a period of time, based upon electrical charge
complementarity
‐
Substances binding tightest to receptor sites are sweetest
Theory of Sweetness – The Details
‐
Tongue receptor sights are either electropositive or electronegative
‐
Sweet‐tasting compounds possess electropositive and electronegative portions to their
molecules
‐
The chemical interaction between sweet sugar molecules and tongue receptor molecules is
thought to initiate the sweet taste transduction event
‐
)n sweet taste transduction, a chemical stimulus, the tastant molecule, is converted into
electrical impulse
‐
The electrical impulse is sent to the brain and interpreted as a sweet sensation
‐
Sweet portion of the tastant is referred to as a glycophore
Unit 5:
Chapter 10 – Food Microbiology and Fermentation
10.1 What are Microorganisms?
o
o
-
Microorganisms are living entities that are too small to be seen with the naked eye
Consists of bacteria, viruses, protozoa, and fungi such as yeasts and molds
Primary function of microorganisms is self‐perpetuation
Many microorganisms utilize organic matter C(O, proteins, lipids, etc to form inorganic
compounds nitrates, sulfates, etc
Parasites and viruses depend on a living host for nutrients and to carry out metabolic reactions
required for growth
All living organisms are classified as either procaryotes or eucaryotes
Procaryotes = no nucleus (includes bacteria’s)
Eucaryotes = contain a nucleus (includes fungi, protozoa, plants and animals)
V)RUSES ARE NE)T(ER because they are noncellular they are considered a life form
Microorganisms have scientific names consisting of a genus name and a species name
Organisms belonging to the same genus share one or more prominent phenotypic, or characteristic
Organisms belonging to the same species share many phenotypic characteristics as well as being
genetically very similar with at least % similarity in their nucleic acid material, i.e. RNA or DNA
Bacteria are unicellular organisms
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o


o
o
o
o
o
-
Found just about everywhere in nature soil, air, water and the intestinal tract of mucous
membranes of animals and humans
Divided into gram‐positive and gram‐negative cells
Gram staining – classifying cells based on whether they retain crystal violet in their cell membrane
or not
Gram‐negative bacteria have thin cell walls and an outer membrane
Gram‐positive bacteria have thick cell walls and no outer membrane
Bacteria are also classified according to their shape: the spherical coccus, rod‐shaped bacillus and
the cell with twists‐ the spirillum
Coccus shaped organisms can also occur in the diplococcus arrangement, where two cells remain
attached after cell division
Rod‐shaped organisms include most disease‐causing bacteria
Some bacteria are able to develop into spores by coating their membrane and cell wall with extra
layers of material in a process called sporulation
Spore development often occurs as a response to unfavourable growth conditions, such as lack of
nutrients or lack of water
)n this state, bacteria are able to significantly increase their survival to processing treatments such
as heating, drying and irradiation
They are in a pseudodormant condition, unable to grow or divide
Once conditions become favourable again, or if exposed to a short heat treatment, the spores
germinate into vegetative cells, resuming growth and metabolic activity
Fungi include two types of microorganisms
Molds – are multi‐ or unicellular and found in decaying matter
Grow in the form of tangled mass called mycelium
Molds of importance in foods multiply by spores known as conidia
Yeasts are unicellular and can grow over a wide range of conditions
Protozoa are single‐celled eucaryotes
Protozoa of interest are parasites
Do not grow in food but require at least one animal host to carry out their life cycle
Most are phagotrophic‐ able to ingest particulate food
One cyst yields several trophozoites – motile parasites that penetrate the small intestine of the
infected animal
Viruses are obligate parasites and host‐specific
Ones associated with food are typically RNA‐containing viruses
Attach to the host cell by receptors and then either inject their nuclear material into the host or
become engulfed by the host
Once inside the host, the virus nucleic acid is replicated using the host s enzymes and virus particles
are synthesized
Most food viruses are considered temperate viruses which insert their nucleic acid into the host s
DNA, leaving the host cell intact
10.2 Factors Affecting Microbial Growth
Nutrient Availability
-
Most nonparasitic organisms can be classified as chemotrophs or phototrophs
Chemotrophic – organisms require chemicals for metabolism
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o
o
-
Chemotrophs can be subdivided into:
Lithotrophic – require inorganic compounds such as minerals
Organotrophic – require organic compounds such as carbohydrates
Phototrophic – require energy in the form of light to live
Nutrient needs depend on the organism and on other factors such as temperature
Water Activity
-
Bacteria have stricter requirements than other organisms
Need quite a bit of water to survive, as measured in terms of water activity – the amount of water
available for microbial growth
Most bacteria require a minimum water activity of . , yeasts = . , and mold = .
At low water activities, microorganisms die because water inside the cell diffuses out in an effort to
balance the osmotic pressure
This migration results in cell death due to dehydration shrinkage
Acidity/ Alkalinity
-
Many bacteria cannot survive at p( values less than . with a preference of values near neutrality
Yeasts can live at p( . with a maximum of .
This broad range enables yeasts to survive in environments not suitable for most bacteria
Molds can tolerate even more extreme p( values than yeasts with tolerance to p( between . to
.
The p( alters a microorganism s ability to transport molecules in or out of the cell through the cell
membrane
)n an acidic environment of low p(, protons saturate the membrane making it difficult for cations to
move in or out
At high p(, hydroxyl ions saturate the membrane, preventing the movement of anions in or out of
the cell
)n addition, proteins which are very sensitive to p( changes are denatured and precipitate out of
solution
Oxygen
-
Amount of oxygen in the environment is also a crucial survival/growth factor for microorganisms
This is talking about the oxidation‐reduction potential of that medium
Redox potential – depends on the ratio of total oxidizing electron‐accepting molecules to the total
reducing electron‐donating molecules in the medium
Oxidized environment means that the molecules have a relatively high affinity for electrons
Reduced environment means that the molecules have a low affinity for electrons
Molds are aerobes requiring oxygen to be present
Some bacteria, notably the ones that cause food spoilage, are also strict aerobes
Most bacteria that cause disease are facultative anaerobes – they prefer aerobic but have the
capability of growing even if oxygen is not present
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-
Microaerophilic – require some oxygen to be present but cannot tolerate the levels present in
aerobic environments, usually % oxygen
Anaerobes cannot tolerate any oxygen, requiring the environment to be completely reduced
Aerobic microorganisms die due to lack of oxygen because of their inability to produce adenosine
triphosphate ATP
Anaerobic microorganisms die due to too much oxygen because of their inability to remove toxic
oxygen‐derived radicals such as superoxide radical from the cell
Temperature
-
Today we classify microorganisms into five categories according to their ability to tolerate specific
temperatures
Maximum growth temperature: the temperature that causes inactivation of an organism s
enzymes and structure damage to the extent that these outbalance the enhanced ability to
synthesize new cell material
Optimum growth temperature: the temperature that corresponds to the shortest generation time
time it takes for the cells to divide , usually a matter of minutes
Minimum growth temperature: is the temperature corresponding to the longest generation time,
usually exceeding one thousand minutes
Psychrophiles: are organisms that prefer low temperature
Psychroptrophs: organisms that prefer high temperatures but can grow at low temperatures
Thermotrophs: tolerate high temperatures
Thermophiles: prefer high temperatures
Mesophiles: a classification to which most disease‐causing microorganisms belong, cannot tolerate
extremes of temperature, preferring the levels found in the tissues of humans and animals
Cell death due to low temperatures occurs because of slowing down of reaction rates during
metabolism and because of a decrease in cell membrane fluidity, which slows down transport of
nutrients into the cell
Death due to high temperatures occurs because of inactivation of enzymes, as well as denaturation of
cell structural components
Food Effects
o
-
Foods that are high in protein can exert a buffering effect, such that microorganisms are able to live
and grow in the food even if the p( is below the minimum levels necessary for survival
Certain components and characteristics of foods can prevent a change in the redox potential of the
food in spite of the oxygen content of the atmosphere in which it is packaged
This is called the poising effect and it depends on the presence of reducing compounds such as some
sugars, the ability of food tissue such as fruit and vegetables to use oxygen and the p( of the food
The more alkali the p(, the more negative is the redox potential, thus the more reduced and
anaerobic the food
Some microorganisms can inherently survive extremes of temperatures through special abilities
Using the Hurdle Concept
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-
Nonlethal levels of the various factors discussed above can be used in combination to inhibit or
reduce microorganisms in foods
For example, combining the absence of oxygen, such as in vacuum packaging, with refrigeration can
inhibit the growth of aerobic bacteria commonly involved in spoilage of fresh meats
)n this example, lack of oxygen and low‐temperature storage act as two hurdles to impede bacterial
growth
The hurdle concept is more effective when several hurdles are applied
10.3 Foodborne Microorganisms
Sources of Microorganisms
o
o
o
o
o
-
Gusts of wind pick up organisms from the soil and make them airborne
Splashing water containing microorganisms against surfaces forms aerosols, causing microbial cells
to become airborne
Air near Earth s surface is more contaminated than air at higher altitudes
The air over land is more contaminated than the air over oceans
The summer months are higher in terms of microbial content of air
What is the effect of water depth?
The more shallow the body of water, the more contamination it has because oxygen from the
atmosphere is readily available for microbial growth
Bacteria survive in lakes and oceans be degrading excess organic material excreted by algae as well
as the remains of dead animals such as fish
Lack of nutrient availability, dry conditions, and low temperature make soil a somewhat hostile
environment for microbial growth
Most bacteria found in soil are spore‐formers because spore production gives them a survival
advantage when environmental conditions fall below optimum
The microbial flora of foods consists of microorganisms originating from the following sources:
Microorganisms associated with the raw food
Microorganisms acquired during handling and processing of food
Microorganisms that survived the preservation and storage treatments applied to the food
Microorganisms in water contaminate sea life, through passage of microorganisms from water to
plankton to fish to humans
Types of Microorganisms Found in Food
-
Three types are most relevant:
those that spoil food,
causing and
those that are useful for food production
those that are pathogenic or disease
Muscle Foods
-
Fresh meat cuts usually have a microbial load of approximately ,
total organisms per gram
Consist primarily of bacteria, yeasts, and molds, although viruses and other parasites can be present
)nterior of the meat is free of contaminants, or sterile
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-
Mechanically deboned meat such as poultry can have contaminants added when the special
machinery removed the bones
Most fresh meat is packaged under vacuum prior to shipping
The population of microorganisms on the meat shifts from primarily gram‐negative bacteria to
mostly gram positive
Most of these organisms are lactic acid bacteria, able to ferment sugars under anaerobic conditions
to form lactic acid
Bacteria are usually present on the outside slime layer of fish, on the gills and inside the intestines
Fruits and Vegetables
-
Since fruits have a low p( they do not support the growth of bacteria very well
Acid tolerant types, as well as yeasts and molds can be found in these products
Contain predominantly lactic acid bacteria
)f this material is composted, a procedure based on fermentation and heat application, pathogenic
organisms can be eliminated before it is used for fertilizer
Dairy
-
Pasteurization eliminates most microbial contaminants
10.4 Food Spoilage by Microorganisms
-
Microorganisms utilize the carbohydrates and proteins in foods as energy sources for cell growth
and reproduction
Metabolizing of Producing Carbohydrates
-
During fruit and vegetable spoilage, C(O s such as polysaccharides, monosaccharides and
disaccharides are metabolized by microorganisms
Organisms containing the enzyme pectin esterase or pectinase can split these bonds, resulting in
fruit and vegetable rot
Cellulose, another polysaccharide commonly found in vegetables is composed of glucose molecules
held together by B‐ , linkages
)n addition to metabolizing C(O s, microorganisms can cause spoilage of foods containing sugars by
producing carbohydrates that alter the texture and flavour of those foods
Both dextran s and levans are responsible for the ropy consistency of spoiled fruit juices and make
up the slime layer that forms on fruits and vegetables
Metabolizing Proteins
-
Aerobic bacteria and lactic acid bacteria produce lactic acid by metabolizing glucose
This causes a souring odour and taste
Levans and dextran s are produced which alter texture
Several anaerobic and facultative anaerobic bacteria utilize amino acids in their metabolic reactions
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Mold Growth
-
Meats are subject to mold growth with changes in meat colour being the primary result
10.5 Microbial Fermentation
-
-
By metabolizing nutrients, microbial cells produce adenosine triphosphate ATP
)f metabolism is carried out under conditions where oxygen is absent, it is called fermentation
One of the ways in which microorganisms metabolize nutrients is called glycolysis
Glycolysis generates ATP through what is called substrate‐level phosphorylation of sugars, with
pyruvate as an end product
The groups of organisms most frequently used for the production of fermented foods are the lactic
acid bacteria
They require amino acids, B vitamins, nitrogenous bases e.g. purines and pyrimidine s and an
optimal p( ranging from to . p( for growth
Homofermentors are organisms that produce one single compound such as lactic acid as a result of
carrying out fermentation reactions
Heterofermentors produce more than one compound
Lactic acid lowers the food p(, imparting unique flavours
Lactic acid bacteria are used as starter cultures to start the fermentation process to produce
cheese, butter, cultured buttermilk, cottage cheese, yogurt, sausage and fermented vegetable
products
Yeasts are used in the food industry for fermentation
The Fermentation of Milk
)n the process of fermenting milk, lactic acid bacteria are used to lower the p( of milk through the
production of lactic acid from lactose
This causes a gel to form when the p( reaches . with precipitation of proteins taking place at p(
.
Besides fermentation by lactic acid bacteria, coagulation of milk proteins can be accomplished by
adding the enzyme chymosin rennet
This reacts with casein, the major protein in milk, forming a gel of calcium phosphate paracaseinate
This type of fermentation is called rennet coagulation
Cheddar cheese is made from pasteurized whole milk
A colouring agent such as annatto is added and the mixture is incubated at degC for approximately
minutes to allow the proteins in milk to coagulate
The product is then cooked at degC and the whey is drained
Cheese is pressed for
hours and more whey is drained
The product is dried for days at degC, covered with wax, and ripened at . degC for up to
months
Cottage cheese is made from skim milk which has been pasteurized
The difference is that incubation is carried out at degC for about to hours to allow for the slow
curdling of the milk
The curd is cut into cubes and cooked at degC
They whey is then drained and cream and salt are added = soft cheese texture
For yogurt – whole milk is heated at degC for
minutes and coked to degC
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-
-
Starter cultures include a : ration of a homofermentor and a heterofermentor
The inoculated milk is incubated at . degC for about hours until the p( drops to . ‐ .
During this hour period a symbiotic relationship develops between the two organisms
Proteases secreted by the organism result in the release of amino acids from the milk proteins
The fermentation process is then slowed down by cooling the yogurt to . degC until the p( drops
to . , at which time growth stops
The Fermentation of Meat
These cultures are usually salt‐tolerant, able to grow in to . percent salt
End product = lactic acid the p( of the meat must drop to . or less to comply with the USDA
requirements
The p( controlled by varying the amount of sugar added, the temperature of fermentation and the
time
Chemical acidulants are alternatives to starter cultures
Glucose delta lactone GDL is an example
)t can be added at a level of . % in products such as sausage to achieve desirable results
GDL must be added in a controlled manner to limit any adverse effects in the product, such as
protein denaturation, an overly soft texture and flavour changes due to the fast p( drop
Semi‐dry sausage containing % moisture is prepared by adding % salt, sugar, seasoning, and
nitrite to cubed beef
Fermenting Fruit and Vegetable Products
-
The starter culture is composed of the normal mixed flora of the raw vegetable
Lactic acid and carbon dioxide are the main products of fermentation
The lactic acid lowers the p( and the carbon dioxide creates and maintains anaerobic conditions
Fermenting Cereal Grains
-
Beer is made with barley, rice and corn as the raw materials
These grains supply C(O s to the yeast
Hops are plant flowers that contain essential oils that contribute bitterness compounds for flavour
and tannis for colour
Barley is germinated and dried, a process that produces barley malt
Germination activates the enzymes needed to break down the starch in the barley malt, releasing
individual sugars
The end products of the fermentation are ethanol and carbon dioxide
Steps involved in beer making vary, according to the style of beer
Malted barley and the cereal grains are cooked together to form a mash
Starches in the grains gelatinize making them more susceptible to enzyme attack
Cooking is carried out at degC and increased slowly to degC so as not to inactivate enzymes
The liquid that results after mashing is the wort
(ops are added to the wort and they are brewed by boiling for . hours
This step sterilizes the wort, inactivates enzymes, precipitates proteins that would affect turbidity
and extracts flavour from the hops
The cooled wort is inoculated with Saccharomyces cervisae and the fermentation is carried out for
approximately days
During this time the p( drops to . and p( can be adjusted to make different beer products
Finally the beer is cooled to degC, filtered to remove the yeast and stored to mellow the flavour
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-
Beer can then be pasteurized at
cans
(ey guys,
degC for
to
minutes or filtered once more before filling into
) literally just took what ) thought were the main points directly out of the text. (ope you're all having a good break and
sorry again that these were not in sooner!
‐Ashley :
Unit 6:
Chapter
: Food Safety
‐food biosecurity is the prevention of intentional food supply terrorism
. What is a Foodborne )llness?
‐foodborne illness is defined as any illness resulting from ingestion of food
‐biological hazards include bacteria, molds, viruses, and parasites, such as protozoa, flatworms, and
roundworms.
‐chemical hazards include chemical substances that occur naturally in foods, such as plant toxins, and
those that are added to food, such as antibiotics
‐physical hazards include bone, metal, plastic, and any other foreign matter that can cause damage to
consumer if ingested.
. Types of Biological (azards in Food
Bacterial Causes
‐bacteria case disease in humans according to the following classification: infection, intoxication, and
intoxification
Foodborne )nfection
‐infectious bacteria are those that invade the intestinal tract, they colonize, the epithelial cells lining
the intestine are damaged, and disrupt the uptake of solutes into the body of these cells, the excess
water is responsible for the loosening of stool, or diarrhea.
‐the damage also sends a message to the brain that triggers the vomiting response
Foodborne )ntoxication
‐those that produce toxin in food during growth
‐if foods are stored improperly in such a way to allow growth and toxin production
‐onset is quick because toxins are absorbed fast by the intestinal tract
Foodborne )ntoxification
‐is cause by ingestion of bacteria that once inside the small intestine, begin to produce toxins
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Myctoxins from Molds
‐are highly toxic substances that some molds associated with foods are able to produce
‐have no apparent usefulness to the mold, yet it is possible that is may use them as a way to use up
amino acids, acetate and pyruvate to prevent over accumulation of these compounds
Virus Transmission
‐transmission of the virus can be through the fecal‐oral route
)ngestion of Parasites
‐typically harbored in the intestinal tract of animals, this turns up as a cyst in the shit of animals and
can be ingested through consumption of undercooked meat, once into the body, the cysts germinate
into growing cells that can persists inside the body for life
‐a flatworm exists in the form of eggs in the soil, cattle can ingest the eggs and the eggs will release
embryos which will eventually penetrate the intestinal tract of the animal, and then they can travel
into other tissues and develop into larvae, consumption of this meat of these animals will cause
disease in humans
. The Most Common Biological (azards in Food
Bacteria‐The Main Culprits
‐in
the leading cause of foodborne illness were all bacterial in nature with more than
of cases being cause by salmonella
percent
‐usually foodborne illness is cause for three reasons: product is not cooked properly in order to
destroy the hazard, product is not store at the appropriate temperature in order to prevent bacterial
growth, or product was contaminated with a bacterial agent and not treated further before
consumption.
Salmonella
‐leading cause of foodborne illnesses in the United States
‐S. Typhimurium and S. enteritids are pathogens in this genus
E. coli O
:(
‐dairy cattle is a primary reservoir for this
Listeria monocytogenes
Yersinia entercolitica
‐found in rivers and bodies of water in contact with wild animals that harbor the organisms
Clostridium botulnim
‐botulism is a paralytic disease, caused by consumption of products contaminated with the organism
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‐most powerful toxin know, affects the nervous system
‐most outbreaks come from foods that are improperly canned at home.
Vibrio cholera
‐foodborn pathogen that has cause the veritable epidemic of cholera in Latin America
‐considered to be leading cause of foodborne illness in Japan where raw seafood is frequently
consumed
Molds‐Ergotism and Aleukia
‐myctoxins associated with foodborn illness are produced primarily by molds belonging to the group
Deuteromycetes.
‐it causes gangrenous ergotism which causes a burning sensation of feet and hands that develop into
loss of circulation, often resulting in limb amputation
‐it also causes convulsive ergotism, the toxin being chemically similar to LSD
‐in the US, grains are considered ergoty if they contain more then . percent of Clavicepts mold by
weight
‐Fusarium mold species can cause alimentary toxic aleukia first stage is a burning sensation in
mouth, this progresses in vomiting, diarrhea, and cramps. Second stage consist of cessation of
symptoms for about two months during which the person feels well‐ during this time the bone
marrow is being destroyed and the person develops leukemia, anemia, and secondary bacterial
infections. )n the third stage, necrosis of the skin and muscles takes place, along with bronchial
pneumonia, hemorrhages in the lungs, stomach and intestines, leading to the death in as many as
percent of the patients .
‐F. moniliforme is found in feed grains like corn, the toxin is produced at near freezing temperatures
and is triggered by temperature cycling from low to moderate to low, it is found to cause esophageal
cancer
‐Aspergillus flavus is another mold that produces a myctoxin of significance to human health
Viruses in Foods
‐hepatitis type A ranks as the sixth leading cause of foodborne illness in the United States
‐it is transmitted by food, associated with shellfish
‐usually transmission is by the fecal‐oral route, with foods subject to fecal contamination due to a
food handler or to contact with sewage
Parasites‐Protozoa and Worms
Protozoa
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‐Giardia lamblia occurs in the form of a pear shaped cyst which germinates upon ingestion
‐one cyst yields trophozoites , which have eight flagella that help propel them by a falling‐leaf type
mobility
‐this protozoa penetrates the intestinal wall but not deeply, causing cramps, nausea, weight loos,
severe diarrhea, vomiting, and flatulence
‐Toxoplama gondii is commonly harbored as oocysts in cats, then it is shed in feces, consumed by
animals sheep and goats , humans ingest oocysts from eating meat or drinking milk, or contact with
car, sporozoites develop in small intesntine, travel through circulation, multiply as tachyzoites and
become embedded in tissue as bradyzoites.
‐Cryptoporidium and Cyclospora are similar organisms, both of which exist as oocysts and are found
in untreated water, once ingested, they give rise to four sporozoites in the intestinal or respiratory
tract, depending on whether the water was ingested or inhaled
‐the sporozoite transforms into a trophozoite and then to a schizont
Flatworms
‐are another type of parasite that can be transmitted via foods to cause disease in humans
‐the tapeowmrs Taenia saginata beef and Taenia solium pork are best now.
‐cattle and swine are intermediate hosts for this parasites hosts in which the parasite develops and
matures , with humans being the definitive hosts host in which the parasite multiplies .
‐eggs in the soil are ingested by cattle or swine, depending on the tape worm.
‐ingestion of eggs can also occur by coprophagy, where feces infected with the eggs are directly eaten
by the animal, the embryos penetrate the intestinal wall of the host and are carried to other tissues
such as muscle, tongue, and heart by circulation, in the tissues they form larvae called cysticerci over
a period of months
Roundworms‐Trichinella
‐most common is Trichinella spiralis, responsible for trichinosis
‐forms lives in the intestine of mammals, the eggs contaminated the soil or feces can be consumed by
animals
‐cysts remain iable inside muscle for up to
years
. What is Mad Cow Disease?
‐one of several transmissible spongiform encephalopathies TSEs specifiacally called bovine
spongiform encephalopathy BSE
‐neurological symptoms result
Transmissible Spongiform Encephalopathies TSEs
‐scrapie in sheep and goats result in loss of coordination and intense itching
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‐kuru is also called the laughing death and is acquired through ritual cannibalism
‐Creutzfeldt‐Jakob Disease in humans cause dementia
‐BSE Mad Cow causes loss of coordination, convulsions, and apprehension in cattle
‐can nvCJD cases in humans be cause by the consumption of cattle with Mad Cow?
Causes of TSEs
‐a prion is the cause of TSEs, prion travels through the spinal cord and reaches the brain, where it
causes damage
‐perhaps it the prion PrP can occur in two forms, a normal conformer and an altered shaped, called
rogue conformer
‐somehow the new PrPsc causes other normal PrPc molecules to change configuration to the beta
sheet, resulting in more PrPsc being formed in a sort of chain reaction
‐this conversion occurs inside neurons and causes the destruction of these cells, causing holes in the
brain
)s PrPsc Transmitted to (umans Through Consumed Beef?
Arguments Against
‐firstly, the more amino acid sequence of the disease PrPsc resembles that of the hosts normal PrPc,
the more likely it is that the host will acquire the disease if exposed to the disease prion proves
transmission from cattle to humans is impossible
‐secondly, it has been shown in laboratory that transgenic mice containing human normal PrPc
produce nvCJD when injected with human disease PrPsc, but not when injected with cattle disease
PrPsc.
‐third, the distribution of CJD and nvCJD in the world does not coincide with the incidence of scrapie
in sheep or of BSE in cattle.
Arguments For
‐argument and evidence that suggests BSE causes nvCJD.
‐first, monkeys injected with BSE prion die from nvCJD symptoms
‐second, hugh numbers of BSE cases in cattle have been shown to correlate in timing to the incidence
of
nvCJD cases in the United Kingdom.
‐third, test have shown a similarity between BSE and nvCJD prions structurally, although not with the
sporadic type of CJD
Why Great Britain?
‐possible reasons is that the British produce more sheep then the US.
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‐second, quite a bit of the feed in the UK used to contain animal by products
‐third, but most significant, the British eliminated the use of steam‐heating of rendered products
. Preventing Foodborne )llnesses
Ways in which foodborne illness cause by biological hazards can be prevented, we can summarize
them into three categories:
preventing or minimizing contamination
preventing or minimizing growth of the hazard
eliminating or reducing the hazard
Preventing Food Contamination
‐the food industry depends on good manufacturing practices or GMPs
‐food should be produced in such a way to minimize contact with contaminated soil, water or air
‐cross contamination occurs when microorganism are transferred from one food to another
‐this is a critical control point that must be minimized through careful processing and sanitation
procedures
‐ a sanitizer is applied just prior to processing to kill any biological hazards such as bacteria that may
remain
Preventing Proliferation of Foodborne Microorganisms
‐temperature is a good method to inhibit microbial growth
‐the range of temperature from
‐
F
. ‐
C is known as the danger zone
‐bacteriostatic use of preservatives that do not kill the organisms but simply prevent them from
growing , bacteria are not able to multiply even though they remain viable.
Elimination or Reducing Biological (azards
‐heat is most common
‐can be used in conjunction with other method such as drying or smoking to enhance bactericidal
ability killing of bacterial cells
‐if effectiveness of this treatment on eliminating or reducing hazards depends on a few factors
type of heat treatment, type of food, type of biological hazard
. (ACCP‐ A Preventative Approach
‐NASA asked Pillsbury and US Army Natrick Laboratories to develop a system that would ensure food
safety for the space program
Principles of (ACCP System
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Conduct a hazard analysis
Determine critical control points
Establish critical limits
Establish monitoring procedures
Establish corrective actions
Establish verification procedures
Establish record keeping and documentation procedures
First step is to assemble an interdisciplinary team. Second step involves a description of the food
being produced and its distribution, developing a flow diagram.
A hazard is defined as any biological, chemical or physical entity that can harm the consumer.
A significant hazard is one that has a high probability of occurrence, given that GMPs are being
followed, or that it is of sufficient severity to warrant its control even the likelihood of its presence is
low.
Critical control points are identified; they are those points or steps during the process for which
control is essential in order to produce the safest food possible.
Critical limits for each CCP are established.
Monitoring of conducting procedures that enable the determination of whether a critical limit is
being maintained or not.
Corrective actions must also be established according to principle , in case the monitoring
procedure reveals the violation of a critical limit.
Principle consists of verification, where procedures are outlines that will help determine whether
control of a CCP is being maintained.
Principle states that records must be kept of all procedures.
Plants must have written standard operating procedures, SOPs, which outline the step by step
procedures they are to follow to comply with GMP standards
This latter is known as an SOP or SSOP, sanitation standard operating procedure, because it describes
an activity involved in the sanitation of a food processing plant.
Key Points
‐foodborne illness is caused by biological, chemical and physical hazards
‐biological hazards include bacteria, mold, parasites and viruses.
‐leading bacterial foodborne pathogens include Salmonella, Escherichia coli O
jejuni, and Listeria monocytogenes.
:( , Campylobacter
‐examples of foodborne mycotoxins are those produced by Claviceps, Aspergillus, and Fusarium
molds.
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‐typical foodborne parasites are the protozoa Giardia, the flatworm Taenia, and the roundworm
Trichinella.
‐foodborne viruses include the hepatitis A virus and the Norwalk virus
‐foodborne illness is typically cause by introducing contaminants into foods, by failing to store foods
at the appropriate temperature, or by failing to process foods properly
‐biological hazards in foods can be controlled by inhibiting their growth through methods such as
refrigeration and the use of bacteriostatic agents, or can be reduced or eliminated by processing
methods such as heating, smoking, antimicrobial agents, or irradiation
‐although not proven foodborne illness, mad cow disease has had a devestatiing impact on the worlds
beef industry and research is needed to establish a connection between contaminated beef
consumption and illness in humans
‐the (azard Analysis Critical Control Point system is a preventative method that can be used to
control foodborne hazards during production and processing of foods.
Unit 7 ‐ Food Processing Part 1
Chapter
Food processing: The conversion of raw animal and plant tissue into forms that are convenient and
practical to consume, and some examples of food processing: mechanical action, heating, extrusion.
Maintains the food's freshness, nutritional value, and to extend shelf life.
Food preservation: The use of specific thermal and nonthermal processing techniques to minimize
the number of spoilage microorganisms in food, making them safe and giving them an extended shelf
life. Examples of techniques: canning, refrigeration, freezing, dehydration, high pressure, irradiation,
and food additives. Loss of food quality due to biological ex. microorganisms , chemical ex.
enzymes or physical changes ex. loss of moisture due to evaporation .
All raw foods are perishable commodities because all foods undergo spoilage and deterioration. One
of the main causes of spoilage is the amount of biologically active water in the tissue. Tissue with
()G( biologically active water will degrade faster ex. leafy vegetables, red meat .
The major causes of food spoilage are: microbial growth, enzymatic reactions, and chemical changes
ex. oxidation . When there is a high water content, and optimal conditions such as temperature, and
p( spoilage will happen. Food preservation is based on manipulating the different conditions. For
example, lowering the temperature will slow down growth. )nhibiting or destroying microorganisms
in foods is using a combination factors of p(, temperature, and chemical preservatives.
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Unit operation: are the broad categories of common food processing operations in practice in the
food industry. Example of unit operations for mixing: agitating, beating, blending, emulsifying,
homogenizing, and whipping.
Examples of unit operations: Materials handling how raw commodities are harvested and
transported to the food processing facility , separating isolating a desirable part of a food from
another part , cleaning removal of debris and bacteria using water and/or detergent ,
disintegrating particle size reduction of foods, cutting meat into small pieces , pumping mechanical
method of moving food from one point to another point , mixing blending of food ingredients to
create a food product , heat exchange removal of heat from a food, roasting coffee beans ,
evaporation removal of moisture from a food to concentrate its solids content , drying extensive
approach to moisture removal, moisture is reduced to a mere few percent , forming foods that are
formed into specific shapes during processing , and packaging protects the food from the
environment and offer convenience for retailers and consumer, could use glass, tin, aluminum,
cardboard, plastic .
Cleaner: amphiphilic compounds with hydrophilic and hydrophobic properties. )nteract with water
and debris to suspend the particles in solution and are washed away.
Sanitizers: chemical compounds with bacteriostatic and bactericidal properties. Bacteriostatic
inhibit the growth of microorganisms, while bactericide destroys microorganisms. Examples:
chlorine‐based, iodophores, quaternary ammonium compounds, and anionic surfactants.
basic principles of food processing: moisture removal, heat treatment, low‐temperature treatment,
acidity control, traditional nonthermal processing, and innovative nonthermal processing. Goal: to
reduce/remove conditions that allows spoilage microorganisms to grow.
Moisture Removal
Achieved through drying, dehydration, evaporative concentration and intermediate moisture
processing. Methods: sun drying for fruits and nuts , drum drying potatoes to flakes , spray drying
dry milk, eggs, syrups, instant coffee , freeze drying freeze product first than evaporate moisture
by a vacuum . Microorganisms depend on the water activity the amount of water not bound to
other molecules , and not the overall moisture content. Molds can grow at a low water activity
. , then yeasts . , then spoilage bacteria . .
(eat Treatment
Forms of heat treatment: pasteurization, blanching, baking, canning to achieve commercial sterility,
extrusion cooking and microwave cooking.
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Nicolas Appert started the idea of canning by first heating sealed glass jars. (eating food in metal
cans by steam under pressure allowed processors to reduce the treatment time at a higher
temperature.





Sterilization: Complete destruction of microorganisms. Ex. usually requires
degrees Celsius of
wet heat for
minutes . May affect texture and flavor of foods if expose to high temperatures for a
prolong time.
Commercially sterile: Degree of sterilization at which all pathogenic and toxin‐producing organisms
are destroyed, as well as any spoilage organisms. May contain bacterial spores, but are inactivated.
Canned/bottled food products: shelf life of years or more.
Pasteurization: Low order heat treatment below the boiling point of water. Specifically target
pathogenic microorganisms, but not all are gone. Refrigeration must be used to extend shelf life to
inhibit the growth of remaining microorganisms.
Flash pasteurization: high temperature, short time (TST treatment where juices are heated for ‐
seconds to a high temperature to kill pathogenic microorganisms. Then cooled and packaged.
Rapid form of aseptic processing. Reduces thermal stress of the product to ensure quality of product.
Blanching: heat treatment for fruits and vegetable to inactivate food enzymes. Common when it is
used to store frozen because freezing will not completely stop enzyme activity.
The specific time and temperature of heating is defined by the thermal death time TDT , which
identities parameters to destroy spores of microorganisms, like Clostridium botulinum.
Low‐Temperature Treatment
Refers to cold storage, refrigeration, freezing. The goal is to cool the food as quickly as possible from
the danger zone of microbial growth ‐ degrees Celsius . (owever foods near the degrees will
maintain the qualities. Freezing will lower the water activity so it will decrease the water available
for bacteria to use.

Direct expansion refrigeration: common method that pumps a gaseous refrigerant through a coil.
Then the refrigerant expands as it moves through the coil, and air moving over the coils cools and
then cools the food product.
Acidity Control
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Refers to controlling p( of a food through the use of acidulants. Low p( can kill microorganisms, but
it can make them unpalatable. Therefore a combination of acidification, heat treatment, and
refrigeration storage are used. The food could have a high acid content normally like fruits with
citric, malic or tartaric acid in there. While acid can be added to the product to achieve commercial
sterility.
Traditional Nonthermal Processing
Antimicrobial chemical preservatives food acidulant additives like acetic and sorbic acid, as well as
sodium chloride, antioxidants , packaging Protection from biological, chemical, physical factors;
packaging in a modified atmosphere packaging MAP prevent oxidation in foods ,
Nonthermal processing innovation
)ncludes irradiation, high pressure, pulses of light and electric fields
(eat Transfer
(ow heat is transferred from a heat source to food particles in a container. processes on heat
transfer: conduction, convection and radiant energy. Conduction is when heat moves through a
material due to molecular motion. Convection is when the movement of heated fluid from hot
regions to cold based on density differences. Radiant heating occurs when heat is transferred
directly between objects without an intervening medium.

(eat Transfer in a Retort Canner

(eat Transfer within a Can

(eat is transferred from a heat source to the food inside each container of food by conduction and
convection to destroy bacteria and spores. Uses steam to heat transfer into the can.
)n conduction, the cold point is in the center of the can since heat is conducted equally on all sides of
the can. While in convection, the cold point is below the center of the can.
Vacuum Canning
Canned foods are packed under vacuum, which means that all air is removed from inside the can.
This prevents the air inside the can from swelling and bursting open if they are stored at a lower
pressure or hot climate. This will also prevent any production of off‐colour and off‐flavour if oxygen
is present.
Thermal Processing for Food Preservation
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Spoilage refers to the loss of food quality as a result of specific biological ex. Microorganism ,
chemical ex. Enzymes reacting with food , and physical changes ex. Loss of moisture . This is
observed by deterioration in food appearance, flavor, odour, and texture. Nutritional properties may
be altered as a result as well. Food preservation is used to delay food perishability and inhibit food
spoilage. Thermal processing targets both spoilage and pathogenic organisms, and their spores.
D value decimal reduction time is when % of the microorganisms have been killed through log
cycle. D values are different for each organism.
(eat Resistance: Ability of an organism to survive thermal processing of a particular time and
temperature combination that destroys non‐heat resistant organisms.
Cell death can be confirmed by chemical changes, like gas production, lack of colonies on culture
plates, and lack of turbidity in broth cultures.
D concept is that the food is processed by
log cycle reductions at a certain temperature. Ex. )n
trillion cans, only spore of Clostridium botulinum survived. With such an unlikely chance of
survival, it is an effective thermal treatment . Temperature:
degrees Celsius for . minutes.
Thermal Death Time TDT graph is where data is plotted on a semi‐log graph paper with time in
minutes on the y axis, and temperature on the x axis. Microorganisms are destroyed by heat in direct
proportion to their numbers in a sample under constant thermal conditions at the same
temperature . )n other words, the same percentage of organisms is killed per time interval.
Ohmic heating is when a food product is subjected to an alternating current in an ionic conducting
solution. The current is applied to opposing electrodes with the food in between. Food can be
commercially sterile without quality being affected.
Traditional Nonthermal Processing for Food Preservation
Food safety can be achieved through the hurdle technology using multiple preservation method to
effectively inactivate microorganisms. Using water activity, p(, temperature, pressure, etc . The
more hurdles, the higher the chance those microorganisms can't adapt to the extreme conditions and
therefore can't grow.
Pulsed electric fields PEF ‐ applies short burst of high voltage to a fluid food placed between
electrodes. )mproves the economy and efficiency of energy usage and to provide microbiologically
safe, nutritious and fresh‐like quality foods. Used for apple juice, skim milk, eggs, pea soup.
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Oscillating Magnetic Fields OMF ‐ (igh energy oscillating magnetic fields inactivates
microorganisms, and denatures enzymes in foods. Can treat solid and liquid foods in flexible
packages, minimize heat treatment, and reduce energy requirements, used for roast beef, milk and
juices.
(igh Pressure Processing (PP ‐ Uses high pressure to kill microorganisms not spores , does not
affect quality of food, not time/mass dependent so processing time is minimal, can be used for eggs,
rice, milk and juices.
Pulsed Light Technology PLT ‐ uses brief bursts of high intensity light energy to cause selective
damage to the cell membranes of bacterial cells without disrupting the food tissue. Can affect yeasts,
molds, spores, and viruses. No effect of quality of the food, and can extend the shelf life. Mainly used
on the surface of packaging materials or food surfaces. Can potentially replace chemical
disinfectants.
Milk Processing ‐ Clarification separate debris from the cream and milk , Adjusting fat content,
Fortify vitamin A and D, pasteurization (TST processing , homogenize separate the cream ,
cooling to . degrees Celsius, then filled and stored.
Cheese is a concentrated dairy food that is allowed to cure/ripen in order to develop the full flavor.
Cheese Processing ‐ Milk is coagulated into a curd using either enzymes ex. rennin or acid. Then
curd is cut, heated and the whey component is removed. Draining, stretching, salting, pressing the
curd. Cheese is cured or ripened ex. lactic acid is form from lactose, development of molds . These
give the cheese different characteristic of flavour, aroma, texture, etc.
)ce Cream Processing – heat the ice cream mix to
degrees Celsius, adding sugar and dry
ingredients to mix, pasteurize, homogenize, aging the mix, freezing creates small ice crystals to give
the smooth texture , filling the containers and hardening at ‐ degrees Celsius. Carrageenan, gelatin
act as stabilizers to control ice crystal formation.
Yogurt Processing ‐ fermented coagulated milk product. Milk is pasteurized, homogenized, heating to
denature proteins to form complexes, cooling to trap moisture, cultures of bacteria is added ex.
Lactobacillus and Streptococcus and these two bacteria stimulate each other's growth , mixture is
cultured and fermented, and the low final p( preserves the yogurt and gives tartness. Flavour is
added. Filling into containers.
Egg Processing ‐ Before processing, eggs are placed in liquid CO to quickly cool to reduce shell
cracks and growth of Salmonella. Eggs are examined for staleness, blood clots, embryo development
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and quality. Then they are broken to separate the egg yolk from the egg white, or mix the yolk with
the egg white. Purified, stored and standardized. Then pasteurization to kill microorganism ,
cooling and dried, packaging and stored.
Meat Processing ‐ Tenderness of meat and grain of the meat, juiciness and flavour are important
quality attributes for meat. Meat toughness is related to rigor mortis where the muscle tissue will
become tough due to actin and myosin forming permanent cross linkages after death. Cold
shortening is a problem in meats when carcasses are cooled quickly after slaughter before glycogen
in the muscle has converted to lactic acid. The muscle will contract due to the cold temperature and
causes toughness in the meat. Thaw rigor is when meat is frozen before rigor mortis, and when
thawed, glycogen is still available allowing for muscle contraction and causing toughness. PSE pale,
soft and exudative meat is the decline of p( in pork after the muscle temperature is too high, this
reduces the ability to hold water.
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Canning – Preservation method. Sealing the meat in a container and then heating it to kill all spoilage
microorganisms. Do not need refrigeration until opened. Convenient since food is fully cooked and
consumed directly from can, but thermal process affects slight flavour and texture changes.
Chemical Additives – Preservation method. Adding ingredients like antioxidants, nitrate, nitrite,
phosphates, salt, sugar to preserve the meat. Salt increases tenderness of meat.
Cold Storage – Preservation method. Refrigeration and frozen storage slows down bacterial growth.
Minimum air contact with the product to prevent moisture loss during storage. )f large ice crystals
form, it will rupture the cell membrane and when the meat is thawed, moisture is loss and quality of
the meat is altered.
Comminution – Processing step. Meat particle size reduction ground, diced, emulsified .
Curing – Preservation method. Addition of salt, sugar, and sodium nitrite to meats for preservation,
flavour enhancement, colour development.
Drying – Preservation method. Removes moisture to preserve the meat so microorganisms cannot
grow. Extended shelf life and can be stored at room temperature. Ex. Dry sausages, jerky . As long
as no oxygen or water is exposed to the dried meat, quality can last for decades. Freeze‐drying is a
low pressure chilling under vacuum where ice crystals form slowly using the moisture in the meat.
Fermentation – Preservation method. Fermentative bacteria when added to meat, produces acid and
contribute to flavour and decrease p( to inhibit growth of microorganism. Ex. bologna
)rradiation – Preservation method. Exposing meat in the package to low‐medium doses of radiation
generated by high speed electron accelerators or gamma sources radioisotopes . Since no heat is
involved, it is sometimes called "cold pasteurization" process. No difference between irradiated and
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o
o
o
o
o
o
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unirradiated meat, except lower microbial count so longer shelf life so high quality product. (owever
when package is open, irradiated meat will spoil like normal food since not sterile and not cooked
the food.
General consumer consumption for irradiated foods are only for low dose < kilogray and medium
dose ‐ kilogray . Gamma sources provide a slower dose rate while e‐beam accelerators provide
a fast dose rate. Foods do not become radioactive after being irradiated as radioactive foods need to
be exposed to a minimum of
MeV of energy. At a high dose, it can cause changes to most food
molecules.
Microorganisms with low water activity drier are more resistant to irradiation than high water
activity foods. Direct effect of irradiation on microorganisms is the collisions of the photons of
radiation with the atoms in the molecule of food, which may alter DNA or proteins as base pairs may
be changed. )ndirect effect is the formation of free radicals during the splitting of water molecules.
Minimize the formation of free radicals by using low dose at low temperatures and use appropriate
packaging for moisture and oxygen barrier properties.
Proteins are not degraded at low doses of radiation and can survive up to
kilograys.
Carbohydrates are broken down by irradiation so gelling and other properties are reduced.
Nutritional and energy role of simple sugars are not affected.
Vitamins are sensitive to irradiation as well as to heat .
)rradiation produces radiolytic products free radicals , but no unique products are found in
irradiated foods so no clear link to cancer. )rradiation is considered a food additive by the FDA and if
it is used to treat food products then it needs a label, but if it is used as a minor ingredient then no
label is necessary. Because of the rise of foodborne illnesses due to bacteria, irradiation has been in
use to treat some foods to kill microorganisms, but due to the public being skeptical about
irradiation and the possible link to cancer, it is not being accepted too well yet. The safety and
quality aspects of irradiated foods should be communicated clearly and honestly to educate
consumers so that they can decide whether to buy irradiated food or not.
Restructuring – Processing step. Flaked/ground beef or pork can be reformed into loaves or portions
resembling steaks. ex. Smoked sliced beef and boneless hams
Smoking – Originally it was only a preservation method, but is also classify as a processing step as
well. Exposes meat to the natural smoke from burning hickory wood to give a smoked appearance
and preserve the meat ex. ham, turkey
Vacuum Packaging – Preservation method. Since many spoilage bacteria is aerobic, removing oxygen
by packing under vacuum can extend the shelf life since oxygen can cause off‐flavours and odours
with unsaturated meat lipids and it can inhibit rancidity in meat.
Fish Processing ‐ Thawing frozen fish processing step , eviscerating processing step; cleaning and
sorting the size of muscle , precooking in steam oven to soften , cooling overnight and separating
light from dark fish meat preservation method , Forming into cylindrical shaped chunks using a
compact machine, filling into cans with added water/vegetable oil, and vacuum sealing and sterilize
in a retort. Curing fish have different types: salted, smoked and pickled preservation method .
Poultry Processing – Slaughter processing step , scalding processing step , defeathering
processing step , feet removal processing step , evisceration processing step , chilling
preservation method; rapid to below . degrees Celsius , packaging preservation method or
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further processing. Commercial cooking for chicken is LTLT low temperature, low time to
minimize quality loss to increase palatability.
Unit 8: Food Packaging
Summary Unit 8: Food Packaging
Development of food packaging materials is one of the fastest evolving areas of the food industry.
This unit provides a brief overview of this topic.
Why are Foods Packaged?
The food industry has been criticized for over‐packaging products which can contribute to waste
disposal problems which we shall also look at in this unit. As far as food packaging goes, the reasons
behind it can be classified into four categories:
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Containment: Containment is an obvious function of packaging. The design facilitates division
of the product into individual units such as cartons, cans or pouches after which the units can
be grouped together.
Protection of product: Protection is important for integrity and food safety. The major reason
for protection is to keep desirable characteristics in and undesirable elements out . For
example, properly packaged coffee keeps the product dry and prevents flavour volatiles from
escaping while moisture, dust etc are kept out.
Convenience: Convenience is important to consumers because of which packaged units
should be light, easy to open, hold, apportioned into suitable serving sizes and facilitate
pouring, reheating and resealing.
Communication: Packaging is used to communicate messages regarding the identity, quantity,
ingredient content, usage, storage instructions, price, nutritional information and
promotional information. Packaging appearance can provide visual cues to consumers and
attractive graphical designs help to influence consumer buying decisions.
Types of packaging materials
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Metal: Metal packaging includes tin cans, aluminum cans and foil. A major problem with metal
packaging is corrosion from exposure to acidic foods. (owever, this problem can be solved by
application of coatings to the inside of cans to shield against corrosion.
Glass: Glass is transparent and completely inert to chemical interactions with food because of
which it is compatible with any food product. Breakage and its relatively heavy weight are
problems associated with glass though. (eavy weight translates into higher costs.
Paper and fiberboard: Commonly used for outer wrappings, boxes and bags. When used as
primary containers, coatings on paper must be food grade non‐toxic and non‐reactive .
Plastics: Plastics are composed of polymers of repeating organic molecules which can be
fashioned into flexible films or semi‐rigid trays and containers which makes them very
versatile. (owever, disadvantages include gas permeability, possible migration of plastic
components into food and temperature exposure limits. Pouches can be made from plastics
that can tolerate high temperature. Laminates are extended applications of the use of plastic.
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Environmental impact of food processing and consumption
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Environmental impact of food packaging disposal: Many food companies realize that over‐
packaging contributes to the burden of landfills. Much of the volume of garbage that is sent to
landfills consists of packaging materials. The National Packaging Protocol is a Canadian
government initiative established in
to promote waste reduction through source
reduction, reuse and recycling programs. The target of NaPP to reduce the amount of
packaging waste to % of
levels by the end of
was surpassed by the mid‐
s.
Many controversial scientific, social and ethical issues exist regarding to the impact of food
packaging upon the environment. Some environmentalists have promoted the return of the
glass milk bottle but a returnable milk bottle has to make approximately forty round trips
before it matches the cost comparison of a pouch pack. Packaging decisions therefore require
consideration of the balance between environmental responsibility, packaging utility and
consumer concerns. For example, consumer concerns to single serving products such as
drinking boxes has been favourable due to the convenience factor but these packages
contribute more waste volume than frozen concentrate cans or larger cartons.
Environmental impacts of food processing: )nvolves problems posed by by‐products of food
processing. Consumer concerns have motivated many companies to re‐evaluate their
approaches to waste management. (owever, there are economic factors that are strong
driving forces. )n some municipalities, companies are handed out fines or surcharges for
treatment of sewage effluent found to be above a certain level of organic matter i.e., BOD .
Some companies have forced management to investigate alternative means of pre‐treating
water as a result of this whereas others have taken on the challenge to recover usable
components from waste products which can be marketed.
Part Two:
C(APTER
p
‐
9.1 PROCESSING OF FATS AND OILS
Lipids with high melting point and are solid at room temperature are called fats.
Lipids with low melting points and are liquid at room temperature are called oils.
All food lipids are mixtures of triglycerides.
Processing of fats is the extraction of a fat or oil from its natural source
Refining refers to the removal of impurities from the extracted oil or fat
Crude oil is the product made after pressing and rendering it is edible
Typical extraction system to get oil from oilseed kernels consists of:
‐ Cleaning to remove dirt and debris
‐ Grinding the kernels
‐ steaming the seed meat
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‐ Flaking the small pieces between flaking rolls
‐ extracting the oil wit solvent
‐ separating the meal or marc from the oil solvent solution
‐ removing the solvent from both the miscella and the marc
Common processing techniques
Rendering: heating of fatty meat scraps in water – allows fat to melt and rise to surface
Pressing: mechanical squeezing of oil from oilseeds
Solvent extraction: separation of oil from cracked seeds using a nontoxic fat solvent such as hexane.
Deodorization: application of steam heat in vacuum chamber to strip away certain odor causing low
molecular weight compounds from oils.
Degumming: first refining step for oils such as soy bean and other phospholipids
Neutralization: removes free fatty acids from a fat
Bleaching: refers to the removal of coloured substances from oil
(ydrogenization: process to saturate double bonds and make oil more solid and resistant to
oxidative rancidity
Winterization: refrigeration treatment of oils for a specific purpose
Plasticizing: refers to softening a hard fat, which changes the fats consistency
Mono‐and diglyceride preparation: refers to isolating these triglyceride derivatives for use as
emulsifiers
Processing of specific fats
Milkfat is a mixture of glycerides found in milk, milk products and butter. )t can be processed
through fractionation so it has various melting points which allows for spreadablity of butter.
Fractionation of milkfat: during dry crystallization process, milkfat is heated and melted and then
cooled under controlled conditions. This creates both solid and liquid phases which can easily be
separated. But when kept together create a product like butter that is both hard and spreadable.
)nteresterifcation: removal of fatty acids from the glycerol portion of food triglycerides.
Chemical and physical testing of fats
Test
purpose
)odine value
Predicts level of fat unsaturation
Acid value
Measures free fatty acid content due to lipid hydrolysis
Smoke point
Measures an oil s heat stability
Peroxide value
Saponification value
Measures peroxide content due to lipid oxidation
Predicts free fatty acid molecular size
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9.2 SUGAR PROCESSING
Most common sugar is sucrose – a disaccharide found in almost all plants. Found in highest
concentrations in sugarcane and sugar beets
Cane sugar refers to the sucrose product obtained from the sugar cane and is generally produced in
two stages because the sucrose decomposes after harvesting the cane.
Manufacture of raw sugar cane occurs in cane‐growing countries, whereas refining occurs in sugar‐
consuming countries.
Sugar beets are processed into white sugar in stage.
Sugarcane processing occurs in the following steps:
Extraction: cane is chopped into chips to expose the tissue and open the cell structure which allows
for extraction of the juice. Crushed cane proceeds through series of roll mills where it is forced
against a countercurrent of water known as maceration. Steams of the cane juice mix with the
maceration and combine into a dilute juice.
Neutralization and clarification: Mixed juice from extraction mills is purified by adding calcium
hydroxide lime and heat which inactivated enzymes and raises p( to neutral.
Concentration and crystallization: clarified juice is pumped into a series of devices called
evaporators, where steam is used to concentrate the juice into evaporator syrup which is ‐ %
sucrose. Concentrated syrup is further evaporated to achieve supersaturation. Addition of mother
liquor produces a solid precipitate. Crystallization is then carried out through a series of steps and
the first produces A sugar and leaves behind the mother liquor called A molasses.
Separation and drying: Crystals and mother liquor are separation by centrifugation – where liquid is
spun off the crystals.
Sugar refining: production of high quality sugars from remelted raw cane sugars
9.3 BEVERAGE PROCESSING
Drinking water is water intended for human consumption and contains no added ingredients.
Bottled water includes natural mineral waters, carbonated waters and sweetened, flavoured waters
that are typically carbonated.
Primary aims of bottled water processing are:
to ensure a safe product
to preserve the properties ascribed to the water, such as mineral content or flavour.
Ozone is an unstable, colourless gas that acts as a powerful oxidizer and a potent germicide and can
be used to sanitize water in bottling plants because it kills bacteria in water.
Soft drink beverages
Term soft drink was originally used to distinguish between alcoholic beverages with hard liquor.
When originally invented and sold soft drinks would contain such drugs as heroine, codeine and
cocaine.
Coco‐cola was patented in
, it originated from a caramel coloured syrup which was diluted and
carbonated. The reason for the name was coco = cocaine and cola= caffeine.
For the production of soft drinks, water quality is critical since poor water can affect, taste, colour ,
odor etc.
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Carbonation refers to the saturation of water with carbon dioxide under pressure in which the gas is
dissolved in the water and becomes carbonic acid.
Most soft drinks are sweetened with sucrose, high fructose corn syrup or fruit juice concentrates.
Diet drinks are sweetened with synthetic sweeteners which include aspartame, acesulfame‐K,
saccharin ad sucralose. All synthetic sweeteners are much sweeter than sugar per gram so less is
used.
Finished soft drinks are produced by diluting the flavouring syrup with carbonated water which is
carried out by automatic machinery.
Special beverage categories
Non‐carbonated soft drinks: produced with much the same ingredients and techniques as with
carbonated soft drinks – however they are usually pasteurized
Powdered soft drinks: made by blending flavouring material with such ingredients as dry acids,
gums or artificial flavour
Nutraceutical beverages: are drinks formulated with special functional ingredients that promote
some aspect of health or reduce risk of certain diseases.
9.4 PROCESSING OF CEREAL GRAINS
Cereal grain processing refers to the conversion of cereal grains into food products or ingredients.
Cereal grains are technically classified as dry fruits
The term cereal technically refers to any grain used for food and grain refers to a small hard seed
produced by plants that are grasses.
Grains are not typically consumed in a raw unprocessed state. The key is milling – grinding the grain
into a form that is easily incorporated into foods or cooked
Wheat milling
There are hard and soft types of wheat grains. The terms describe the firmness of the kernels and
relate to the strength of the gluten developed when doughs are made from milled flours.
Flours developing strong gluten have high protein content, with an elastic gluten suited to
breadmaking.
Flours developing weak gluten have low protein content and are more weak and fragile producing a
softer more fragile dough better for cakes and biscuits.
Semolina is used to make pastas and is the result of milling hard grains. Doughs made from it are
strong but not as elastic as strong gluten flour.
Breadmaking
Bread is the product of baking dough from a mixture of flour, water, salt, yeast and other
ingredients.
Flour‐to‐water ratio is about :
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Patent flour is the purest flour, has very low mineral content and is about
% protein
Breadmaking process involved mixing ingredients until the flour is converted into stiff dough,
followed by baking the dough into a loaf. Dough must be elastic enough so that it can be stretched
when pulled.
Gluten is formed from two proteins present in flour: gliadin important for stickiness and glutenin
important for elasticity
Process of bread making:
Flour, water, other ingredients  mixing  fermenting
sheeting, molding and panning  Baking  baked bread.
degrees C for
hrs  Proofed dough 
Pasta processing
Pasta products are known as cooked and dried alimentary pastes. Semolina, not flour, is the proper
form of cereal used to make pasta.
Semolina is coarsely ground durum wheat, a type of high protein hard wheat – strong gluten, but not
as elastic.
9.5 FRUIT AND VEGETABEL PROCESSING
A vegetable is a plant or plant part that is served either raw or cooked as part of the main course of a
meal.
A vegetable‐fruit is sometimes referred to as the fruit part of a plant that is not sweet and is usually
served with the main course of a meal.
A fruit represents edible, sweet tasting fleshy seed‐bearing ovary flowering plants.
Most fresh fruits are high in water and low in protein and fat. Good sources of both digestible
carbohydrates and indigestible carbohydrates.
As a group, fruits are good sources of vitamins, minerals, natural sugars, organic acids, fibre and
phytochemicals
Harvesting is the collecting of fruits and vegetables at the specific time of peak quality and colour,
texture and flavour. The correct harvesting time depends on the intended use of the fruit.
Climacteric fruits and vegetables continue to ripen after harvest ex. banana
Nonclimacteric fruits and vegetables must be harvested when ripe.
Ripening
Maturity represents the stage of development when the fruit is picked, at or just before ripening.
Ripeness is the optimum or peak condition of flavour, colour and texture.
Ripening refers to the transformation of a fruit from an immature stage of development that has
undesirable eating attributes to one that is palatable.
Respiration is the biological oxidation of organic molecules to produce energy plus carbon dioxide
and water. Respiration is an essential role in postharvest fruit and vegetable ripening.
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Transpiration is the loss of moisture through pores in the tissue.
Both respiration and transpiration contribute to fruit perishability.
Fruit development can be divided into three major phases: growth cell division and enlargement ,
maturation reached at the end of growth and senescence associated with deterioration process
Processing
Trimming refers to detaching superfluous plant parts from fruits and vegetables that are being
processed into specific products
Washing involves the use of water as a soaking medium or direct spray
Blanching is used to inactiviate the enzymes responsible for browning and tissue softening in fruits
and vegetables.
Packaging
Typical packaging involves a simple plastic breathable bag or over‐wrap.
Modified Atmosphere Packaging MAP has also been developed. With MAP, the barrier properties
of the material are carefully selected according to the respiration characteristics of the fruit or
vegetable. The objective is to provide an optimal storage environment so that freshlike attributes
are maintained. This technology produces what is called minimally processed vegetables MPV .
MPVs normally do not contain any preservatives and have not gone through any heat or chemical
treatment.
Storage
Managing temperatures where fruits and vegetables are stores is critical to maintaining quality.
Warm storage temperatures promote microbial growth and chemical changes. The rate of chemical
reactions in fruit is generally double for every increase of
degrees.
types of cooling are used in the food industry. Hydrocooling which is the immersion into cold water
and vacuum cooling which is the practice of moistening food items and then placing them under
vacuum to induce evaporative cooling.
)f the temperature is too cold it can damage the fruits and vegetables and that is called chilling
injury.
Hypobaric storage is low pressure storage which can maintain quality of fruits or vegetables for
several months.
Freezing
Works very well for vegetables of all kind, the more rapid the freezing, the more improved texture
upon thawing.
Frozen fruits and vegetables offer high quality nutritive value
Manufacture of fruit juice
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Processing of fruit juice involves
‐ washing
‐ extraction
‐ clarification
‐ preservation via pasteurization
key steps:
Fruits and vegetables are washed prior to being processed into juice.
Filtration systems using diatomaceous earth are employed in juice filtration systems, the juice that
results is devoid of particulates and is of excellent clarity and transparency.
Frozen juice concentrates are produced by passing the juice through an evaporator
Canning
(arvestingreceiving  washing  grading heat blanching  peeling and coring  can filling 
removal of air under vacuum  sealing/closing  retorting/heat treatment  cooling  labeling 
packing
Hermetically sealed container is any package, regardless of its composition that is capable of
maintaining the commercial sterility of its contents without refrigeration after processing.
Can be stored at room temperature for years.
Due to the severe heat treatment, some canned goods exhibit inferior quality and lower nutritive
value that fresh and frozen food.
Aseptic canning is practiced in the processing of certain fruits and vegetables. Presterilized
containers are filled with a sterilized, cooled product. The product is sealed into a sterile
atmosphere with a sterile container cover.
Pickling
Chemical preservation, acid is used to preserve the products. With pickling, acetic acid vinegar ,
salt sugar or alcohol can be added to preserve the fruits or vegetables.
Dehydration
Among the oldest and most common forms of food preservation.
Moisture is driven off by the application of heat, resulting in a stable food product that has a
moisture content below what at which microorganisms can grow.
Virtually unlimited shelf life when under proper storage conditions and offers concentrated source
of nutrients.
basic systems for dehydration:
‐ sun drying
‐ hot air dehydration
‐ freeze drying
Hot break/cold‐break processing
Turgor is the structural rigidity of plant cells due to their being filled with water. Most important
factor in determining texture of fruits and vegetables.
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Objective of the Hot break process is to inactivate the enzyme activity of pectinase and results in a
product rick in pectin, of high viscosity and with a very low syneresis ketchup, tomato paste etc .
Cold‐break process uses no heating, which allows pectinase to lower the viscosity of the product.
Results in a slightly better colour and flavour and delivers a product with low pectin, lower viscosity
and higher synersis juice, soup etc.
9.6 SOY BEAN PROCESSING
Leguminous seed that is grown widely around the world.
Nutritionally inferior, the wild soybean has been domesticated and crossed to produce a soybean
rich in oil and protein.
One method of soybean processing uses an expansion/expelling method in which raw soy beans are
fed through a series of augers, screeners and controlled rate feeders into the expanders. The beans
experience extreme temperature and pressure conditions in the expanders and the oil cells of the
bean are ruptured as the product exists the expander. The high temperature cooks the meal and oil,
yielding a high quality food grade product and moisture is released as steam. The hot meal slurry
from the expanders is fed into a continuous oil expeller where the meal is squeezed under pressure
and the free oil is expelled. Two products are recovered from this process: soybean meal and
soybean oil.
Soybean meal exists press as dry powder and chunks , high quality product containing % oil,
protein and % dry matter
Soybean oil flows from press and is collected in basin, screened and recycled back into the press.
Semi‐clean oil results which is pumped through filter press to the final storage tank
%
Low cost extrusion process can be employed to produce textured soy protein products that offer
excellent protein quality and low fat from soy flour. Protein texturization refers to a process that
creates a fibrelike structure in a proteinaceous material. This process is the basis for texturized soy
protein.
Soy ingredients are also used in sports beverages, two common types are soy protein isolates and
soy protein concentrates.
9.7 CHOCOLATE PROCESSING
Chocolate is a food derived from cacao beans.
Cocoa butter is the form of fat found in cacao beans.
Cacao beans are harvested, cleaned, fermented for ‐ days to develop initial flour compounds, dried
to remove much of the moisture and shelled to produce the nibs.
Following that, the nibs are roasted to develop flavour, after roasting the shells are removed and the
beans are ground. Grinding generates enough heat to liquefy the fat in the beans. This results in the
separation of liquid called chocolate liquor which is % fat and a mixture of carbohydrates,
proteins, tannis, ask and about % moisture plus some caffeine.
When originally produced, it is just bitter baking chocolate. To make milk chocolate, mix chocolate
liquor with milk solids or unsweetened condensed milk and the proper amount of cocoa butter to
achieve % fat level.
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Lechithin may be added to improve flow behaviour and the stabilize ingredients. Conching
contributes important flavour and texture.
Conching is the slow mixing process
+ hours with heat added to increase product thickness and
smoothness
Tempering of the conched product refers to the manner in which temperature of the product is
manipulated to achieve the development as the desired stable crystal structure of the finished
chocolate.
Polymorphism is the ability for a fat in this case cocoa ot be solidified into six crystal forms
depending on the conditions of tempering.
Bloom is a visual defect that can appear on the surface of chocolate that removes the glossy
appearance.
Unit 9: Food Engineering and Physics
Part: 1‐
Food Engineering – Chapter
All food molecules are in motion due to the energy they possess. Molecular motion depends upon the
temperature and the phase of the food material.
Molecular motion varies in the individual states of matter, apart from temperature. At any particular
temperature, the molecule of solid, liquid, and gaseous substances have a different range of motion.
)n spite of these differences, each state of matter will respond identically with the addition of heat
energy: Their molecular motion increases, as a result that is measurable as an increase in
temperature.
Heat transfer:
Conduction, convection, radiation
Conduction or conductive ‐ occurs at molecular level – the molecules of food gain thermal energy
from the stove, which causes them to vibrate more rapidly. These vibrations are passed along from
molecule to molecule in the food, although there is no physical movement of the food material during
conductive heat transfer.
Convection or convective heating: When heat exchanged between either liquid or gas and solid
surfaces. The gas or liquid is a fluid substance, and the solid is nonfluid.
Radiation offers another form of heat transfer. All materials, not only the sun emit electromagnetic
radiation based upon their surface temperature. The transfer of heat between surfaces by radiation
depends on factors:


The emissivity of the radiating surface and the absorptivity of the other surface.
The shape and design of the object are also important.
Microwave is part of the electromagnetic spectrum; are long in wavelength, high in frequency, and
low in energy.
Conservation of mass
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Mass is a measure of the amount of matter in an object and is the property that makes an object
reluctant to change its state of motion or no motion, if at rest
The law of conservation of mass says when a reaction takes place; the total mass of reactants is equal
to the total mass of products formed plus the mass of reactant remaining. All changes in matter are
accompanied by a flow of energy. )n addition to heat, energy exits in many forms, such as chemical,
electrical, mechanical, and radiant energy. )f there is no accumulation of mass within the system, the
law of mass conservation simply asserts that the material input through the system equals the
material output through the system. This defines the STEADY STATE.
Steady state has to do with the nature of heat transfer and refers to system properties that do not
change with time. For example, when a heat transfer process is operating at a steady state, the
temperature in the system remains constant in time, although it may vary from location to location
within the system.
)n transient heat transfer unsteady state system properties do change with time.
Thermodynamics
st law: A change in the thermal energy of the system is equal to the heat added to the system minus
the work done by the system – Conservation of Energy – Total energy is neither increased nor
decreased in any process, energy can be transformed from one kind to another, but the total amount
remains constant.
law: (eat will spontaneously flow from a hot object to a cold one, but the reverse and the natural
process tend to move toward a greater state of disorder rather than order. Entropy is a quantitative
measure of disorder in a system.
nd
Heat transfer
Refers to the manner in which heat energy is transported from food s surroundings to the surface
and interior of the food. The driving force for heat transfer is temperature difference. Mechanisms:
Conduction: When heat moves through a material due to molecular motion.
Convection: Due to the movement of a heated fluid from hot regions to cold regions.
Radiation: Occurs when heat is transferred directly between objects without an intervening medium.
The rate of heat transfer is influenced by food thermal properties such as specific heat and thermal
conductivity and rheological properties such as viscosity, as well as by product density and thickness.
Heat capacity and specific heat
(eat capacity of a material is the amount of heat energy necessary to speed up its molecules enough
to raise the temperature of a unit mass of a material by degree Celsius.
Specific heat Cp is the ratio of the heat capacity of a material to that of water.
Heating and chemical changes
(eat energy can cause chemical, physical, sensory and nutritional changes in foods. As a general rule,
the rate of a chemical reaction doubles for every
degrees Celsius increase in temperature.
Heat exchangers
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A heat exchanger is specialized equipment that is used in food processing and storage to either add
or remove heat from food. A wide spectrum of food products, ranging from canned vegetables,
canned meats, fluid dairy foods, and dried fruits and grains receive heat processing treatment.
Heat transfer, mass transfer, and boundary layers
In deep‐fat‐frying:
Conduction within a solid food material
Convection occurs between oil and the food material
Boundary Layers: Dividing lines or fronts as two dissimilar materials, the heating oil and the food
material come in contact with each other. At the boundary layer, it happens heat transfer and mass
transfer.
A frying potato will experience thermal changes to its constituent macromolecules of starch a
protein, as gelatinization and denaturation, respectively. )n addition, color and flavor development
occur, as well as the loss of moisture due to vaporization and mass transfer, and oil uptake though
mass transfer.
Mass transfer
Mass transfer refers to the movement or migration of a liquid such as frying oil or a food
component, either within one phase or between different phases, which is caused by physical
conditions i.e. concentration gradients present in the liquid oil/food system. Mass transfer is
characterized at the molecular level by mass diffusion, and macroscopically by bulk mass transport
as material flow is directed by convection.
At this point, similarities and differences between heat and mass transfer might become apparent.
There are some common threads, including the existence of boundary layers, flow rates and
resistance to flow, physical changes, and the ever‐present adherence to the second law of
thermodynamics, the tendency of systems to move toward equilibrium.
Food material science – A physicochemical approach
The mobility of water in foods and the relationships between water mobility, food ingredient and
polymer mobility, and physicochemical phase transitions, are important factors that influence food
quality.
Four physicochemical states characterize the movement of water and ingredient molecules in food:
crystalline,
liquid,
amorphous rubbery, and
amorphous glassy. Most foods are
multiphasic, meaning they consist of both amorphous rubbery and glassy areas, plus water. )n foods
of varying water content, ingredients shift between these physicochemical states or phases as a
function of temperature, concentration and time. Water and molecules in foods may undergo
physicochemical phase changes during processing and storage, these changes are significant because
they influence food stability and quality. Freezing and evaporation are examples of conditions that
promote such changes.
Crystalline: A structure having the lowest mobility, ex. )ce
Glassy: An amorphous structure combining solid and fluid features; high polymer viscosity, low
polymer mobility, ex. Crisp toast
Rubbery: An amorphous structure combining solid and fluid features; low polymer viscosity, high
polymer mobility, ex. soggy bread. When foods transition to rubbery phase due to moisture
migration, they lose their crispness.
Liquid: A fluid structure having the highest mobility, ex. Water
Glass transition Tg : refers to the change in the physicochemical state of amorphous food materials
between the solid glass and the liquid or rubbery states. The temperature range over which this
transformation occurs can help predict the storage life and stability of foods.
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Glass transition temperature T g of food materials range from very low water to relatively high
high molecular weight food polymers such as starch .
Water acts as a plasticizer in low‐moisture and frozen foods, lowering the glass transition
temperature of food polymer materials. Water‐soluble polymers such as polysaccharides and
polypeptides become plasticized by water and can then undergo the transitions between various
states. Water being available to microorganisms during storage or water that alters texture during
storage are examples of links between physicochemical state, molecular mobility, and food storage
stability, quality, and safety.
Mobility of food molecules and ingredients
)n the amorphous rubbery and glassy states, ingredient molecules retain mobility but become
increasingly constrained as their concentration increases.
Example: Uncooked pasta is made up of starch, and the starch contains amylose and amylopectin
polymers in an organized, hard, glassy condition. )f this glassy pasta is added to water and heated, a
transformation occurs in the organization of the starch because the water plasticizes the starch
polymers. The pasta absorbs water as it cooks, and the glassy condition changes to the rubbery
condition at the glass transition temperature of the polymers. The pasta is no longer dry and hard,
but has become wet and soft.
Caution: Consider a brick of cheese in the refrigerator at degrees Fahrenheit, compared to the same
sitting out for an hour on the counter at
degrees Fahrenheit. The warmer sample will seem more
rubbery – but the reason is mainly the effect of temperature on the proportion of solid crystals to
liquid oil in the lipid molecules in the cheese, not on polymer mobility due to water migration. Fats
harden in the refrigerator and soften soft crystal melt at higher temperatures, but the change has
nothing to do with water.
Food ingredients, as small molecules glucose, maltose or long polymers amylose, pectin
molecules , possess mobility. Polysaccharides can twist, rotate, and exhibit motion. As their
concentration in a food increases, their mobility decreases but physical interactions entanglement
between polymers that touch one another occur. This process of molecular entanglement and
aggregation is what leads to an amorphous rubbery and glassy state. The highly dense, disordered
nature of the amorphous state is quite distinct from low‐density, highly ordered structure of the
crystalline state.
The least stable amorphous state for food ingredient is the rubbery state. )n this state, there is
mobility and low viscosity – viscosity is the friction within a fluid that prevent from flowing freely.
Shelf stability and other quality problems of food ingredients may occur. On the other hand, the more
stable amorphous state is the glassy state. This comparatively dense state is characterized by
minimum polymer mobility and maximum viscosity.
Processing or storage of product well above the glass transition temperature may result in
deteriorative food changes as the food shifts from the solid glassy state to the liquid‐like rubbery
state. On the other hand, the closer a food is to the glassy state transition temperature, the less likely
it is to undergo dynamic phase shifts between liquid, crystalline, and rubbery.
Food microstructure – influencing physical and sensory qualities
Food microstructure refers to the organization of food structures at the microscopic level and their
interactions to produce a food product s physical and sensory characteristics. Texture/structure
relationships are important considerations during food processing because the natural
microstructure of foods can be altered, giving rise to new arrangements of molecules as a
processed microstructure in gel, emulsion, or low‐moisture food systems .
For example, consider the microstructure of ice cream that represents a highly complex food system.
)n terms of phase and systems, it is not only foam G/L , but a colloidal dispersion S/L and an
emulsion L/L . Lactose molecules and casein molecules are colloidally dispersed within an aqueous
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matrix containing frozen ice crystals, while air cells incorporated into the fat phase during mixing are
surrounded by emulsified fat droplets. Although individual molecules of casein and lactose are too
small for detection, the microstructural elements of ice cream that can be seen with a microscope
include air cells, fat, and ice crystals.
Sensible heat is the heat energy in an airstream due to the temperature of the air.
Latent heat is the heat energy in an air stream due to the moisture of the air.
Part 2:
Chapter
pages
‐
13.6 Rheology – studying flow and deformation
What is rheology?
‐science that is concerned with the flow and deformation characteristics of food materials;
measurements include viscosity, fluidity, elasticity and plasticity of nonsolids.
Why is rheology important?
‐provides information about food s structure
‐aids in design of food processing equipment
‐provides vital information related to food s shelf life
‐data can be correlated to sensory data
‐helps in product development
Structured fluid – low modulus material having solid‐like and liquid‐like properties simultaneously
due to its three‐dimensional inner structure examples: suspensions, emulsions, gels, and foams .
Stress – force needed to cause the rupture
Strain – distance the gel will bend before it actually breaks
Low stress to strain (ratio) gel: a small force causes rupture after much movement by the gel
rubbery gel low modulus/structured fluid exhibits this
High stress to strain (ratio) gel: moves only a small distance before rupturing due to experiencing
a large force brittle gel .
Mushy gel – low stress and low strain
Tough gel – high stress and high strain
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Viscosity – friction within a fluid that prevents it from flowing freely type of rheological
measurement ; dependent on physical and chemical changes of food, pressure, temperature, sample
homogeneity and sample turbulence.
Absolute Viscosity = shear stress / shear rate
Surface tension – the force per unit length that acts across any surface; unrelated to viscosity.
Texture – represents both a physical property and a mechanical behavior of food that takes into
account a food s size and shape dimensions, its density and whether it has a porous or nonporous
surface
Plastic, fluid and elastic food materials respond differently to shear stress forces, see page
book for a diagram of this.
Plastics – material is ultimately deformed by stress
in
Elastics – material is stretched by stress but ultimately recovers
Fluids – material moves as a result of stress
Viscoelastic – have behavior of both viscous and elastic material example of bread dough ; if
stretched bread dough will spring back to its original shape.
Newtonian foods vs. non‐Newtonian foods
Newtonian foods are homogeneous mixtures that exhibit no change in viscosity as the rate of shear
is increased examples: water, honey, milk, juice, vegetable oils, etc. . Non‐Newtonian foods are
heterogeneous mixtures that exhibit a change in viscosity as the rate of shear is increased examples.
Tomato paste, mayonnaise, margarine, xanthan gum thickened products, cornstarch suspensions,
etc. . See page
in text for more examples .
Thinning pseudoplastic and thickening dilatant fluids cause viscosity of the fluid to
decrease and increase, respectably, as shear rate increases.
13.7 Extrusion Technology in the Food Industry
Extruders are used to shape foods. Types of extruders are single screw extruders, which are
widely used to produce cereals, pasta and pet foods; twin screw extruders, which are popular
with snake food manufacturers and works better with viscous or sticky foods than does the single
screw; single reciprocating screw extruders, which unlike the others create only minor elevations
of temperature and pressure due to screw and mixing actions.
Unit 10: Toxicology and Biotechnology
Part One:
Chapter
:
‐
Chapter Objectives:
. List the three types of food toxicants, citing specific examples
. Evaluate a dose‐response curve
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.
.
.
.
.
.
.
Explain the possibility of cyanide toxicity from eating certain vegetables
Describe the toxicity of domoic acid arising from shellfish consumption
Discuss the safety of herbal products
Explain the structure and mechanism of cholera toxin
Describe the problem of antibiotic resistance and how it relates to human health
Decide if growth promotants BST and DES are harmful and why
Explain how pesticides might be present in a fast food meal
. Discuss the distinction between a food allergy and a food intolerance
What is a Food Toxicant?
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A toxicant is a chemical substance that can elicit a detrimental effect to ta biological system
Endogenous
Produced by tissue cells in plants and raw materials
Protect plant from pests
Transmission to people can occur through consumption of animal that has ingested the toxic plants
Naturally occurring
Produced by organisms that contaminate the food products
Microorganisms fungi, bacteria, etc can produce these
Synthetic
Synthetically produced which enter food supply via contaminated food processing environment
Can include drug residues in foods of animal origins
Risk Assessment for Chemical Hazards
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Dose‐response assessment: determining the concentration of toxicant needed to cause unfavourable
effect on biological system
Exposure assessment‐determining the risk of exposure of a biological system to a toxicant
Acute effects: take place quickly
Chronic effects: appear slowly
Bioassays: animal studies used to predict the effects of toxicants on humans
Cell culture studies: observe the effects of toxicants on specific cells
Modes of action of toxicant:
Change certain body function e.g. respiratory rate or heart rate by increasing or decreasing speed
)nactivate enzyme activities
Can have wide spread effects or be localized to particular area or organ
Assessing dose response
Dose response: the relationship between a toxic reaction the response and the amount of toxicant
received the dose
Threshold level: dose above which adverse effects are produced
Effective dose ED : an adverse effect seen in % of animals tested
Legal dose LD : will kill % of animals tested
Large LD :
mg/kg
ug/kg
Small LD :
Carcinogens: chemical toxicants which cause cancer
Endogenous Toxicants
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Flavonoids: organic molecules that impart colour and flavour
)nclude: flavones, flavonols, flavanonols, flavanones, leucoanthocyanins, anthocyanins, catechins
Found in plant tissues, secretions and cells
Can impart pigmentation to foods and can promote or inhibit plant growth
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Some have antioxidant activity ability to inactivate toxic oxygen radiation
Absorbed in G) tract and excreted in bile or metabolized by liver
Goitrogens are responsible for producing goiter in humans and death in some farm animals
Found in cruciferour vegetables broccoli, cauliflower, brussel sprouts
Goiter is condition caused by the enlargement and atrophy of thyroid gland
Coumarins cause a pleasant citrus aroma
Found in peel of citrus fruit
Can cause dermatitis due to bergapten, psoralen, xanthotoxin and isopimpinellin which are
photosensitizing agents which cause oversensitivity to light
Cyanide compounds contain cyanogenic glycosides which are converted hydrogen cyanide, a
powerful toxicant, when ingested
)nhibit respiration of body cells
Cassava is vegetable crop containing linamarin, a cyanide based chemical
)s eaten daily by people in West Africa, who consume enough to have an average daily dose of the
dose required to kill a person each day
(erbal extracts are natural compounds often used as a substitute for synthetic medicines
Pyrrolizidine alkaloids are toxic compounds found in )ndian herbal teas, tomatoes, potatoes,
eggplants, etc
These inhibit the enzyme cholinesterase which breaks down acetylcholine which results in
overstimulation of cells
Can also cause stomach pain, nausea, vomiting, difficulty breathing and death
Sassafras root contains % safrole which is a known carcinogen
Sage has been used as abortifacient to induce abortions
% effective in women ‐ days after
drinking quart of tea made from it
Toxic Mushrooms: all mushrooms contain at least one toxicant hydrazine though in food
mushrooms these levels are low enough to avoid health effects
Protoplasmic poisoning affects the liver and kidneys
Amantin poisoning:
Occurs after period of ‐ hours
Symptoms of , persistent vomiting, and watery diarrhea, as well as thirst and lack of urine
)rreversible damage to liver, kidney, heart and muscle occurs, and death follows within a few days
due to necrosis of liver and kidneys
(ydrazine:
Produced by all mushrooms
Toxicant called gyromitrin is produced by G. gigas and Gyromitra esculenta
Symptoms include feeling of fullness, as well as vomiting and headache
Central nervous system and liver are affected, but death rate is low
Orellanine poisoning:
Long period with no symptoms days‐ weeks then nausea, headache, chills, muscle aches, and can
case kidney failure
Neurotoxin Poisoning affects the central nervous system
Muscarine poisoning is caused by )nocybe genera
Profuse sweating, increased salivation and lacrimation, nausea, diarrhea, blurred vision and
laboured breathing can occur
Psilocin and psilocybin toxins can produce symptoms that mimic drunkenness and hallucinations
Gastrointestinal poisoning causes G) irritation
Symptoms include nausea, diarrhea, and abdominal cramps
Naturally Occurring Toxins
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Marine toxins are often ingested via shellfish and finfish containing toxins
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dinflagellates are algae which are consumed by fish, which are then consumed by humans
ciguatera is caused by consumption of tropical herbivour fish red snapper, grouper and cause
diarrhea, vomiting, and abdominal pain with phenomena, muscle aches, tingling, dryness of the
mouth and chills all occurring
Paralytic shellfish poisoning is caused by consumption of mussels, clams, oysters and other shellfish,
and cause numbness, tingling, aphasia, and death due to respiratory paralysis
Saxitoxins cause these symptoms by binding to nerve cells and preventing adequate transmission of
signals from the brain to the muscles
Neurotoxic shellfish poisoning is caused by ingestion of oysters and clams, and symptoms include
tingling, muscle aches, vomiting, diarrhea and possible respiratory irritation
Diarrhetic shellfish poisoning is caused by the consumption of clams and mussels, and symptoms are
acute diarrhea within a couple minutes of ingestion
Amnesic shellfish poisoning is caused by mussels , and is due to a toxin called domoic acid which
causes short term memory loss, disorientation, vomiting and diarrhea
Scombroid poisoning can cause rash, hives, nausea, vomiting and diarrhea, as well as headache,
tingling, flushing, and itching
Microbial toxins are produced by microorganisms, either molds or bacteria
Staphylococcal enterotoxins affect the intestinal system
Cause fever, vomiting
Can only be killed by heating food to
C for at least
minutes
Chloera is an enterotoxin that involves the G) tract causes diarrhea
Verocytotoxins target the kidneys and block protein synthesis, causing kidney failure
Clostridial Toxins affect the G) tract and result in diarrhea
days of ingestion
Produced by C. botulinum which causes death in as little as
Synthetic Toxicants
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Antimicrobial Agents are drugs used to prevent infections that affect the health of food animals, with
drug residues left in meat and milk
Therapeutic treatments are used to cure or treat a certain condition
Prophylactic treatment is a preventive measure
Modification of function drugs are used to promote growth of animal
Antiprotozoal drugs are used to eliminate protozoan infections
Dewormers are used to eliminate parasitic intestinal worms
Antibiotics are used to treat or eliminate bacterial infection
Antibiotic resistance is when microorganisms develop resistance to the antibiotics they are exposed
to
Without an effective means to control their growth, resistant pathogens could proliferate in the
human body causing serious illness
Growth promotants are hormones used to enhance or suppress the growth of specific body cells
Diethylstilbestrol DES is a hormone that promotes muscle build up, however was banned in
as it was classified as a carcinogen
Bovine somatotropin BST is a hormone given to cows to increase milk production
)t is structurally different from human growth hormone so that it does not effect human growth
)t is also % destroyed by pasteurization, and the remainder is broken down by the body s
digestive enzymes
Pesticides are used to prevent, control or eliminate insects or other pests
(erbicides are used in the same way to prevent unwanted plants such as weeds
Maximum residue levels are set as low as possible
Organochlorides are lipid‐soluble and highly stable
Can remain in soil for month, and can accumulate in root plants
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Not easily absorbed through skin
Organophosphates do not persist in the environment, but are easily absorbed through the skin
Prevent contamination of crops with soft bodied insects such as boll weevil
Can cause birth defects, and dermatitis
Carbamates have not been proven to be carcinogens to humans, though are highly toxic
Can cause spasms, low blood pressure and may lead to respiratory failure and cardiac arrest
Fumigants are used to eliminate insects from grain, soil and spices
Was banned due to carcinogenic properties
Plant hormones are used to reduced shoot formation and increase resistance to disease
Very low carcinogen levels
See Figure . for diagram on how pesticide residues end up in fast food meals
Essentially residues are concentrated and extracted, and come together in large doses in fast food
meals
Food Allergies vs. Intolerances
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Allergies are reactions of )mmune systems to component of food, usually a protein
Can cause skin irritation, diarrhea, vomiting, or anaphylaxis which is difficulty breathing and low
blood pressure, which can lead to death due to suffocation
Food intolerances are caused by sensitivities
Some substances include: aspartame which can cause brain damage , MSG, sulfites which can
cause lung irritation , Gluten those who have this suffer from celiac disease , dairy products
diarrhea or vomiting can occur
Challenge questions
What is the key feature of a true food allergy that distinguishes from other adverse reactions to food?
Antigen production by body
Which statement is correct?
Aspartame is not an allergen
Which is the correct sequence?
)gE binding, increased intracellular calcium, histamine release
Why must care be taken to find a nutritionally adequate replacement food when a particular item
like milk has to be excluded from a child s diet due to suspected intolerance?
a. Child is at risk of developing a nutrient deficiency
5. Which is not a reason why food allergies are thought to be common?
a. Foods or additives trigger antigen antigen‐antibody responses in about of adults
1.
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Part 2:
See attached file
Unit 11: Sensory Attributes of Food
Sensory Evaluation and Food Product Development 15.1 What is sensory evaluation?Sensory evaluation‐
the assessment of all the qualities of a food item as perceived by the human senses. )t can involve describing food
colour, texture, flavour, aftertaste, aroma, tactile response and even auditory response
‐ sensory analysis
used more correctly used interchangeably with sensory evaluation Institute of Food Technologist define sensory
evaluation as:
scientific discipline used to evoke, measure, analyze and interpret human reactions to
characteristics of foods and beverages as perceived by the senses of sight, smell, taste, touch and hearing Figure 15.1
(refer pg.421)
• Sight‐ colour, texture, size, shine, shape •
Odor‐ volatile flavour substances •
Taste‐ sweet, sour,
bitter, salty•
Touch‐ sensation of: warm, hot, cold, pain, texture, astringency
•
Sound‐ pop, crackle,
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pouring, fizz, bubbling
A Quantitative Science
• sensory evaluation is a quantitative science where numerical data collected to establish relationships between
product characteristics and human perception •
in sensory studies human stimuli are quantified
•
sensory science in conjunction with product development determines individual preferences of one product over
another
•
sensory specialist define precisely what is to be studied and measured
฀
must choose correct null hypothesis and alternative hypothesis
฀
test design must leave no room
for subjectively and take account known bias sources ฀
must minimize amount of testing to produce accuracy
฀
nature of test subject must be determined ฀
only draw conclusions unambiguously
supported by results
Sensory Science in the Food Industry
• main application for sensory science is quality assurance and product development
•
for max. benefit
sensory evaluation department interacts with other departments sensory specialist interact with packaging and
design, quality assurance, marketing research, legal services
•
primary interaction is in support of
product development and research
15.2 Sensory Odor, Flavour, and Mouthfeel Perception
• types of senses involved in sensory perception: chemical taste and door and physical sight, sound, touch
•
Character notes: sensory attributes of a food that define its appearance, flavour, texture and aroma differ
in meaning from top notes‐ most immediate, prominent sensory flavours in particular food or drinks
Taste
• organ of human taste gustation is the tongue
•
Taste‐ the sensation derived from food as interepreted
through tongue‐to‐brain sensory system •
four primary taste sensations of sweet, salty, sour, and bitter and a
fifth umami delicious trigger brain response •
receptor of tongue pg
fig .
•
taste is thought
as a chemical sense
฀
)nvolves detection by taste buds located on surface of tongue of various food stimuli molecules that are
perceived to have taste, called tastants ฀
contact between stimulus and taste bud is critical for taste
sensation
฀ taste sensation result of a swarm of chemical signals inside the taste buds that culminates in
release of neurotransmitter molecules
• Taste buds‐ epithelial receptor cells organized in clusters of ‐
and embedded into structures called papillae
฀
human possess different types: foliate, circumvallate, fungiform, filiform ฀
taste receptor cells
detect taste stimuli and transfer taste information to brain ฀
newborns have
to
taste receptors
adults:
to
declines with age
• PROP, ‐n‐propylthiouracil ‐ a chemical substance to identify detection threshold people differ in sensitivity to
this chemical
•
categories of tasters in response to PROP
฀
Supertasters: have strong food dislikes, talk about hating a food, can detect specific ingredients in food
samples ฀
Medium tasters: tend to like all foods, fussy about preparation, think about food in an eager, positive
way
฀
Non‐tasters of PROP: can taste other flavours, difficulty distinguishing different ingredients in food,
think food in terms of healthfulness rather than taste, attentive to presentation of food and environment they eat,
more dependant on smell, prefer higher sweetness
Transduction and Sensitivity
• tongue linked with brain through CNS central nervous system •
Taste transduction‐ brains response to
taste stimuli
•
Depolarization‐ when a positive charge accumulates in cell making membrane potential
less negative than normal and more positive •
neuron signalling‐ release of neurotransmitter to brain
฀
salt and sour taste involve similar mechanism of depolarization and release of neurotransmitters
Odor (fragrance, aroma)
• Odor‐ sensation derived from food as interpreted through olfaction sense of smell or door perception
mechanism
•
components of aroma can be either olfactory sensations rancid or fruity perceived by
olfactory nerves or nasal feelings pungent perceived by nose's tactile nerves
•
Olfaction‐ refers to the
perception of odours by nerve cells in the nasal area •
Air‐bourne odourants molecules that possess door
sensed by the olfactory epithelium •
Olfactory epithelium‐ outer layer of receptor cells located on the roof of
the nasal cavity •
Odorant molecules sensed by million of tiny, hairlike cilia that cover this epithelium
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•
optimal contact time between odourant and nasal receptors occur within to to seconds •
exposure beyond this requires receptors to readjust for about
seconds before a new full‐strength sensation
can occur •
sensitivity of olfactory receptors greater than taste
•
sensitivities involved: being able to
detect something at a lower threshold of concentration and being able to differentiate one odour from another
•
humans‐ low threshold of detection compared to animals but ability to discriminate different odours is
equivalent
฀
distinguish several thousand of odours but only couple hundred taste variations
Flavor
• result from chemical stimulation of tongue taste buds, olfactory apparatus, and organ of feeling present within
mouth throat and nose •
Flavour‐ overall impression combining taste, odour, mouthfeel factors, trigeminal
perception
•
trigeminal nerve important neural region that runs through entire facial area
฀
located in the nasal and oral cavities and responsible for trigeminal/ somatosensory perception ฀
such perception refer to sensation of astringency, burning, cooling and warmth
• researchers perceived food flavour is at all areas of the tongue despite each four primary areas •
sensitivity to each taste varies, it is never zero at any area of this taste organ
•
flavours can be
influenced through use of flavour enhancers or potentiators MSG, isotonic acid, maltol
•
Aftertaste‐
distinct from taste sensations are perceived after the initial primary taste response and should be viewed as
residual sensations thats linger on the tongue after swallowing •
Retro‐inhalation‐ major role in flavour
perception refers to the passage of flavour stimuli from mouth through pharynx up to the nose
Mouthfeel
• Mouthfeel‐ perceived sensation of food by epithelial lining within the oral cavity that includes tactile sensation
as well thermal response
•
manner which small movements of tongue press food against gum and palate
perform evaluation of viscosity and texture
•
Example of thermal mouthfeel sensation include coolness
and heat menthol and capsicum in cayenne , metallic mouthfeel food with iron and copper and astringent
mouthfeel tannins in tea
•
Gravy an example of how taste, aroma, mouthfeel, and aftertaste all contribute
to flavour perception
•
•
15.3 Sensory Texture and Color Perception
Sensory Texture
·
Structure and composition of food involves food molecules, perception and measurement
·
•
·
•
·
•
•
Texture perception occurs when food is chewed or beverages are swallowed
Texture measurement involves physical characteristics of food
·
Sensory cells in mouth, tongue, and throat perceive food particle shapes sizes, thickness and hardness, and
transmit information to the brain in a manner analogous to taste and odour systems
Sight and sound create expectation regarding how texture will feel inside mouth upon chewing
·
Cues received by tactile cells in fingers and transmitted to brain via CNS
·
(ardness: described by amount of force required to compress food between teeth
·
Cohesiveness: described by degree to which food will deform or compress between teeth before it breaks
•
Mechanical Sensory Characteristics
·
Due to attractive forces between molecules in food and opposing force of disintegration
•
o
•
•
•
o
)ntensities range from soft through firm and hard carrots, peanuts, hard candy
)ntensities range from easy to disintegrate through difficult to disintegrate celery, grapes, toast, chips
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•
·
•
·
Food chewiness: length of time in seconds required to chew food sample at steady rate one chew per
second with a constant force applied that results in a food consistency that is just ready to be swallowed
•
•
o
Sensory viscosity: related to force required to draw fluid food from spoon across tongue at steady read
)ntensities range from thin to thick through viscous honey, water, ketchup, juice
o
)ntensities range from tender to chewy through tough meats, licorice, cheese, gum
o
)ntensities range from sticky to tacky through gooey broccoli, peanut butter, cream cheese, bread
·
Viscosity
•
·
Related to size and shape range from chalky to gritty to grainy and coarse
•
o
Coarse indicates large particle size, seen in cooked oatmeal
•
•
·
Food adhesiveness: mechanical parameter because it is related to surface properties rather than forces of
attraction and breakage forces required to remove food material that attaches to the mouth upper palate during
normal chewing
•
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•
•
•
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•
•
•
Factors which contribute to a food's sensory texture:
·
Adhesiveness
·
Afterfeel
·
Chewiness
·
Cohesiveness
·
Fat
·
(ardness
·
Moisture
·
Particle shape
·
Particle size
•
Geometrical Food Characteristics
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Related to size of discrete food particles present in food, shape and orientation
•
•
o
Grainy indicate food‐containing grains of specified size wheat germ, farina
•
·
Particle shape and orientation vary from fibrous to cellular and crystalline
•
o
Crystalline indicates foods composed of crystals granulated sugar
•
•
•
•
o
Fibrous indicates foods composed of fibers meat fibers of cooked chicken , steak
·
Afterfeel: analogous to aftertaste in terms of food texture indicates that after certain foods are chewed and
eaten or beverages sipped
o
a texture sensation residue persists microscopic amounts of matter continue interacting with sensory
receptors and oral lining, providing ongoing stimulation and sensation of texture
·
Fat and moisture content: fat absorbed into food during preparation and processing and released into
mouth upon consumption
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•
•
•
•
•
•
o
Due to chemical differences, fats vary with respect to melting behaviours
o
Moisture can vary from dry cereal grains to moist cake to wet tomato slice and watery canned fruit
o
Ex. salt sodium chloride diminishes perceived sourness of food acids and enhances sweetness or sucrose
o
Eggs rolls, chicken tenders, doughnuts, onion runs oily and greasy
Sensory Interactions
·
Foods, being complex systems, exhibit interactions in terms of taste, odor, texture and flavour
o
Sucrose counteracts saltiness of salty foods
•
·
Sensory overload: results when saturation of sensory system occurs excessive sensory stimulation occurs
•
·
Colour: pigment molecules as chemical basis of colour
•
•
•
•
•
•
•
o
o
Wavelengths rage of
‐
nm acts as stimulus to sensory cells in eye, which communicate signals to
brain, enabling us to see colours of foods and beverages
o
Colour used as indicator of economic value of products recognized as quality parameter that standardizes
product
o
§
(unter colour difference:
§
L measures lightness or darkness values range from
·
Red +a
•
§
•
•
•
components of tristimulus: shade of darkness of a sample plus hue components
·
o
•
Measurement of color accomplished through analytical technique of tristimulus colorimetry
§
(unter tristimulus data used for food analysis useful and correlates well to visual colour because it is
patterned after light‐sensing principle of eye retinal receptors
•
•
Sensory fatigue: occur when excessive number of samples are presented to panelists for evaluation
ΔE : ΔE = ΔL + Δa + Δb
(ue is measured by the (unter a and b scales
·
Green –a
·
Blue –b
·
white to
black
Yellow +b
15.4 Responses Contributing to Sensory Perception
Sequence of events in sensory perception:
.
Stimulus interacts with sense organ tongue, nose, eye and converted into nerve signals to travel to brain
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.
.
•
•
Brain interprets incoming signals and organizes them into perceptions
Response elicited from subject based upon perceptions
Objectivity and Subjectivity
·
Difference between sensation and perception can be viewed as difference between regarding brain as
machine objective brain function vs. regarding brain as thinking mental process subjective brain function
subject to conditioning, preconceptions, natural ability etc.
·
Sensations correspond to objective functioning, while perceptions are subjective
•
Objective procedures:
·
Flavour, texture, colour, odor can be measured using test equipment
•
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o
Can measure amount of force needed to shear food sample into pieces, which might then be used as an
index to tenderness, or a colour meter can be used to determine product s colour
Eliminates bias not sufficient indicators of product quality because it doesn t measure subjective response
)ntensity: product stimulus, while sensitivity has to do with panelist ability to sense degree to which character
note is present, as determined by its product concentration and perception by a person intensity of stimulus refers
to its perceived strength
·
Measurement of sensory attributes evaluated over period of time following initial exposure is time‐intensity
measurement
o
time‐intensity curve shows the total duration of a taste, the maximum intensity, the time required to
achieve maximum, and the rate of intensity decline to a minimum value
Threshold: sensitivity refers to distinct points of transition for sensory judgments corresponding to concentrations
of stimuli
·
each person has lower limit at which he or she first begins to respond to stimulus and extended range for
ability to differentiate low, medium, high levels of stimulus
·
detection threshold: point at which person initially responds to stimulus, the dividing line between lack of
sensation to sensation
·
recognition threshold: point at which identity of stimulus is made
·
difference threshold: refers to minimum amount of stimulus change that results in change of sensation
·
terminal threshold: amount of stimulus above which any increase in intensity can t be detected without use
of reference standards
Section 15.5: Sensory Tests
·
Specific tests cannot provide definite answers part of larger info gathering
·
Sensory specialist has expert knowledge of available sensory tests applies correct test to solve given
problem
·
Sensory research: main guiding principle = project objective determines sensory technique and test chosen
·
Other Principles:
o
No trained panellists for acceptability judgment
o
No consumer panels for descriptive info
o
No individuals involved with R&D product aspects on panel
o
Samples label with random ‐digit code = min bias
o
Samples orders randomized avoids artifacts due to order of presentation
o
No panelist interaction in sensory evaluation so no data bias
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Classification of test methods:
• ·
Sensory tests classified by primary purpose and most valid use
• ·
test most used:
a.
.
Affective
b. .
Discrimination
c.
.
Descriptive
• ·
Each have different goal and selection criteria for panellists
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Affective Test Method:
·
Affective tests = quantify degree of liking/disliking a product from another include preference, hedonic,
consumer acceptance tests
·
approaches in sensory evaluations by consumers = measuring . preference and . acceptance
·
Preference: consumer choice between products of hedonic like/dislike basis
·
Ranking: form of preference testing with more than samples NOT rating
o
Panellists order products by either degree of liking or perceived intensity of sensory attribute
·
Rating: meaning panelists assigns numbers to characterize products by categories sensory attributes
type of acceptance test
·
Consumer acceptance testing:
o
Consumer rates liking/disliking on scale
o
Generates average value from all data linked to food s acceptability
o
Scale may be implied ie. Specialists convert like extremely to score of or dislike extremely score of .
o
Large panelist number
‐
or greater to represent typical end user
Discrimination Test Method:
·
Discrimination Tests: answer whether difference exists between products
·
Test between control and test sample
·
Data analysis based on stats of frequency and proportion
·
Critical # of consistent correct judgments made above level expected by chance guessing shows ability of
panelist to discriminate.
·
Examples: difference‐from‐control, duo‐trio, paired comparison, triangle test used to determine if
panellists can discriminate between treatments table . – sensory test overview
·
Sensory specialist determines which test to use from diff. criteria ie. )f chemical difference then paired
comparison test used ie. Quantitative difference, then triangle test.
·
Triangle Test: products, samples, of product, and of other product presented in specific order if A
= product and B = product – possible presentation = AAB, ABA, BAA, BAB, ABB. )f panellist consistently picks
out odd sample = statistically significant/ true sensory difference
·
AAA and BBB never used
Descriptive Test Methods:
·
Descriptive test: describes product attributes flavour, texture, mouthfeel, etc. by quantifying perceived
sensory characteristic intensities
·
Descriptive analysis = most comprehensive/info‐sensitive evaluation tool requires trained panellists
familiar w/ attribute scale
·
Words used = precise and careful so not ambiguous
·
Scorecards used include info on specific characteristics evaluated
·
Quantitative descriptive analysis (QDA): developed by Stanford research test uses line scales, replicated
sxperimental design, descriptive terminology, and analysis of variance
o
Data in spiderweb/ radar plot form intensity of each sensory attribute increases outward radially from
centre point
·
Flavour + texture profiling use descriptive analysis detailed product description developed by trained
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•
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a.
b.
c.
d.
e.
f.
g.
•
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•
•
•
•
specialists.
·
Flavour profile method: odor, taste, flavour, mouthfeel notes determined by panellist
·
Sensations quantified in terms of intensity, order of perception, duration, from initial sensation through
sensation lingering after swallowing.
·
Texture profiling: mechanical, geometrical, fat & moisture, and afterfeel described and quantified in
similar manner.
Selection of Test Method:
·
Sensory test selection involves large number of decisions.
·
Decisions apply to nature of food product and project objective, panellist selection/training, experimental
design, and statistical analysis.
Section 15.6: The role of the sensory evaluation specialist in product development
·
Sensory program useful in helping in food industry:
o
To meet consumer expectations
o
Enhance potential for product s market success
·
Role/importance of sensory defined by correct application of tests coupled to proper panellist training &
use, and awareness of factors ie. interactions
The Sensory Specialist:
·
Sensory specialist plays imp. role in developing project objectives, and enables product development by
collaborating in development of experimental design.
·
key roles of sensory specialist in product development:
1.
Determine project objective by understanding needs of project leader to apply sensory test and analyze
data. Define treatments & variables, and if it is new product or product modification
2.
Determine test objective deciding to determine difference/preference/acceptability. Before starting
study record project objective, test objective, and brief statement of how test results obtained/analyzed/applied
3.
Screen samples in st discussion phase. Sensory specialist examines all sensory properties of samples to be
tested for any biases ie. colour, thickness differences
4.
Design test by test technique selection, score sheet design, panelist selection & training, sample
preparation/presentation criteria, and data analysis type
5.
Conduct test sensory specialist ensures design requirements met by sensory staff
6.
Data analysis using analysis determined in final design stage data analyzed for main treatment effect test
objective and other variable ie. presentation order, day effects, subject variables
7.
Interpret & report results review results and express them in terms of objectives. Written sensory report
summarizes data, describes samples, provides panelist info., identifies key test findings, and make informed
recommendations.
The Sensory Environment:
·
Layout & environment of sensory testing area carefully planned to minimize distractions so panelists focus
on sample evaluations
·
Accomplished by individual sensory booth, seating, partitioning.
·
Booth colour = neutral shade
·
Temp. control
·
Two‐way hatches/sliding doors between scientists and panelists to pass samples and retrieve score sheets
·
Separate panelists from sample prep area and have ventilation in testing room to keep out competing
odours.
·
No communication between panelists so no biases and distraction
·
Computer terminals in booths so panelists can input data as they perform evaluation easier for sensory
scientists.
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Unit :
15.7 PRODUCT DEVELOPMENT
 ‐ Product development: process in which new food product ideas are generated and
the products themselves are created and marketed. )t involves the conceptualization,
formulation, processing, testing, and marketing of food products
o ‐ The product may be novel, or an improved existing product
o ‐ New product ideas present challenges to the manufacturer in terms of
development cost, formulation, testing, and marketing strategies
o ‐ Thousands of new product ideas are generated annually, but most fail.
o ‐ The scientific method is used in product development to keep it organized
and
effective. They follow a defined sequence of steps to introduce the new
product
to the customers
 ‐ product development team: all of the individuals employed by a food
manufacturer who play a role in the product development process
‐ All technical, marketing, financial, production, and quality assurance personnel.
The Scientific Method in Product Development
 ‐ Scientific method used to develop ideas and solve problems
‐ Define a problem/ask a question
‐ Solve the problem/answer the question by forming a hypothesis ‐ Test the
hypothesis through experiments
‐ Accept or reject the hypothesis based on data analysis
 ‐ Value‐added food products: products that offer the consumer some improvement
in terms of quality or convenience over the traditional or previously available foods
‐ Eg. )nstant pudding‐ value added since you donʼt need to prepare it
The Stages of Product Development
 ‐ A number of stages are needed to develop a product. They involve creativity,
expertise, and cooperation to get from initial product to marketing
 ‐ Corporate mission: statement that embodies the foundational aspects of any
corporation: who it is, what are its products, and who are its customers
‐ This is the starting point. Form this mission a number of objectives are generated
 ‐ Product strategy: plan that is established to accomplish a companyʼs mission and
objectives
‐ eg. Market many forms under the same brand name steak fries, crinkle‐cut fries,
etc
 ‐ Product line: similar products that differ according to some characteristic but that
serve in the same market
‐ Eg. The above examples
 ‐ Feasibility: determination of whether a new product can be developed in terms of
formulation, equipment and costs
‐ Could you have a microwaveable french fry product?
 ‐ Line extension: new form of an established product or family of products ‐ eg. New
flavour, low‐fat version, etc
‐ The more creativity, innovation, and technical complexity required, the more
developmental time and cost required. But a line extension is relatively inexpensive to
create compared to those from scratch
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‐ The three general stages of of product development under which specific activities fall are:
idea stage, development stage, commercial stage
‐ Idea stage: initial stage of product development
 ‐ )dentify the idea, concept, problem, or special challenge which the
development team works with.
 ‐ The problem should be framed to meet corporate objectives and should
be feasible
 ‐ Requires input from food scientists, engineers, marketing and
management individuals of a food company
‐ Development stage: the second stage in product development involved in creating
the design and nature of the product, from a compositional standpoint as well as a
processing, packaging, and marketing one
 ‐ The majority of the activities in product development occur in this stage.
 ‐ From formulation to process fine‐tuning, to use of sensory and analytic
testing
 ‐ Bench‐top prototype: product made in the laboratory as a small scale
a few pounds in weight batch that can be easily and reproducibly formulated for
repeated testing without too much expense
o ‐ One of the first accomplishments of this stage is to form this prototype
o ‐ These are made in facilities called pilot plants scaled down versions of
actual commercial production facilities
‐ Commercial stage: the third stage in product development ‐ production
scale‐up from pilot plant to commercial plant, plus market testing and the
subsequent introduction of the new product to a national market
 ‐ Product development scientists interact with manufacturing and operations
personnel in the actual commercial production plant
 ‐ The consumer also plays a part in this stage by providing information through
market testing and market research. Market testing and market research are
distinct processes
o ‐ Market testing occurs after the production of the product in a commercial
production plant. )t involves a Test market: location where the new product
is sold to consumers . Feedback is obtained through surveys after the product
has been used in their own homes
o ‐ Market research: organized inquiry that seeks to identify and measure the
factors that influence the consumer marketplace, so as to guide marketing
professionals in decision making regarding new products
15.8 THE ROLE OF MARKETING IN FOOD PRODUCT
DEVELOPMENT
 ‐ The difficulties related to new product development can be envisioned as a three‐
dimensional challenge.
‐ Technical expertise required of product development scientists
‐ The complexity of the marketplace, influenced by competitors and the economy ‐
difficult to predict consumer factors changing needs and wants
 ‐ the marketing department must be paying attention to the needs of the consumer
and communicate these to upper management
 ‐ Brainstorming: in marketing, examining consumer trends to speculate on what
new products would meet those trends.
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‐ This is important in identifying new products that the consumer really needs. Thus,
new product development is market‐driven
Marketing Steps
Market trends ‐> ideas: brainstorm ‐> focus group ‐> in‐house testing ‐> consumer
testing ‐> test market
 ‐ To determine the productʼs marketing potential it is necessary to discover which
factors
ingredients and processes have the greatest impact on consumer response
 ‐ Focus groups: interactive panel composed of about
consumers plus a trained
moderator to obtain detailed attitudes regarding the concept of a processed new
product
‐ This process speeds up product development, reduces biases, and determines how well the
product fits with the original concept. This group can also identify further potential product
functionalities health benefits, convenience, sensory pleasure
 ‐ After the focus group, the next step is to actually evaluate or test the concept. A
prototype is made, and in‐house sensory testing guides further prototypes and testing
until the product matches the original concept and satisfies consumers.
 ‐ Consumer response testing: asking consumers questions regarding the likelihood
they would purchase a product, how much they would pay for it, and how frequently
they anticipate using the product. Affective testing is also a component of consumer
response testing
‐ This information is brought to corporate management who will decide whether to
proceed with the product or not
 ‐ The next step is test marketing, which was discussed earlier. This stage involves the
operations end of the company engineering . This stage is very expensive millions
of dollars but the cost is lower the debt from just sending the product out nationally
and having it fail.
‐ Success at this level suggests success in the national market, but there is still only a or %
chance of success. Which is crazy since the company has probably spent about $ million
plus on the product to get it to the national market
Meeting Market Need and Product Marketability
 ‐ Market need = the need by the consumer for the product. Thus it is important to
identify the targeted user in terms of demographics.
 ‐ Demographics: information such as age, gender, income and geographical location
of consumers and factors such as shopping habits, level of education, and motivation
to buy
 ‐ Consumer habits change with time and trends
 ‐ Marketingʼs primary role is to monitor the marketplace for changes that might
influence
the course of new product development. Value‐added products can be developed to
meet particular market needs.
15.9 PRODUCT PROBABILITY, LIFE CYCLE, AND ANN
Product Probability
o ‐ Probability: ratio of the number of favorable outcomes to the number of
total possible outcomes both favorable and unfavorable . range = ‐
 ‐ probability means that there is no possibility of a favorable outcome
 ‐ .
means the favorable outcome is certain
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‐ Therefore, probability is used to predict the information such as a
products
likelihood of success
‐ the overall probability of success in going from the starting product, to the
final product
is calculated by multiplying all the individual probabilities from each
intermediate stage.
‐ The total time and cost required in producing the final product can also be
determined from the intermediate steps. This data is important when judging
whether the produsct
should be continued or not
Product Life Cycle
‐ Product life cycle: birth of a new product, its duration as a good selling item,
and the time required to see sales decline and the productʼs removal from the
marketplace
‐ There are distinct phases of this life cycle
 ‐ )nitial period/lag phase: low sales, but high advertising and
promotional costs
 ‐ Growth phase: indicative of successful promotion and consumer
acceptance.
New and repeat purchases drive sales
 ‐ Static phase: sales peak but no longer increase over time
 ‐ Sales decline: can accelerate rapidly especially if competitors
anticipate and
capitalize on the new market trends
‐ this cyclic characteristic of products suggests a need for ongoing product
development
programs
‐ A successful company will have a new replacement product ready before a
product life
cycle decline is seen for each of its product lines
Artificial neural network
‐ Artificial neural network (ANN): form of computer intelligence that uses
electronic sensors for instant pattern recognition and product information
processing.
‐ This will supplement human sensory testing, and would be beneficial since
unlike humans, it is not subject to fatigue or emotion

o
o
o
o
o
o
o
o
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