June 4, 2014
4. Recommended nutrient intakes RNIs are replaced by Dietary reference intakes DRIs
Nutrition Research
- Research begins with a question. Eg, what foods or nutrients might protect against the common
cold?
- In search of an answer, scientists make and educated guess called a “hypothesis”
- Then systematically conduct research studies to test each hypothesis
Research Studies (Designs)
1. Epidemiological studies: scientists observe how much and what kinds of foods a group of
people eat and how healthy those people are
Their findings identify factors that might influence the incidence of a disease in various
populations
Eg. The people of the Mediterranean region drink lots of wine, eat plenty of fat from olive oil
and have lower incidence of heart disease than northern European and North Americans
2. Case-control studies: Researchers compare people who have a given condition such as a disease
with other people who do not have the disease
They closely match them in age, gender and other key variables so that difference may account
for the condition in the group
Eg. People with goitre (enlarged thyroid gland) lack iodine in their diets.
3. Animal Studies: Researchers feed animals special diets that provide or omit specific nutrients
and then observe any changes in health. (can be more controlled than human diets)
Such studies test possible disease causes and treatments in a laboratory where all conditions
can be controlled
Eg. Mice fed a high fat diet eat less food than mice given a lower fat diet so that they receive the
same number of kcalories, however, the mice eating the fat rich diet become severely obese.
4. Human intervention (or clinical) trials: Scientists ask people to adopt a new behaviour (eg. Take
a vitamin C supplement) and compare their results to a control group taking a placebo. These
trials help determine the effectiveness of such interventions in the development of prevention
of disease
Eg. Heart disease risk factors improve when people receive fresh squeezed orange juice daily for
two months compared with those on a diet low in vitamin C, even when both groups follow a
diet high in saturated fat.
Blind experiment: an experiment in which the subjects do not know whether they are members
of the experimental group or the control group. (double blind = neither groups know)
Nutrition Assessment
-
A comprehensive evaluation of a person’s nutrition status, completed by a registered dietitian
or physician, using:
o Historical information (health, socioeconomic, drug and diet)
o Anthropometric data (physical measurements)
o Physical examinations
o Laboratory tests
Historical information:
- Personal medical records may reveal a disease that interferes with the person’s ability to eat, or
the body’s use of nutrients
- Person’s family history of major diseases that have a genetic tendency to run in families
- Economic circumstances may show a financial inability to buy foods, or inadequate kitchen
facilities in which to prepare them
- Social factors such as marital status, ethnic background and educational level also influence food
choices and nutritional status
- A drug history may highlight possible diet medication interactions that lead to nutrient
deficiencies
- A diet history can indicate whether the diet may be under-supplying or over supplying nutrients
or energy
Anthropometric Data:
- Measurement of the physical characteristics of the body such as height and weight
- The assessor compares measurements taken of an individual with standards specific for gender
and age or with previous measures of the same individual
Physical Examination:
- Looks for clues to poor nutrition status
- Every part of the body can be inspected for clues such as the hair, eyes, skin, posture, tongue,
fingernails, etc
Laboratory tests:
- Takes samples of blood and urine and analyzes them in the laboratory. The results are compared
with normal values for a similar population
Useful terms:
Malnutrition: any condition cause by excess or deficient food energy or nutrient intake, or by an
imbalance of nutrients, (ie, “mal” = bad).
Undernutrition: deficient energy or nutrients
Overnutrition: excess energy or nutrients
Nutrition Assessment of Populations
- Researchers conduct surveys similar to those used on individuals
- The data collected are then used by various agencies for numerous purposes, including the
development of national health goals
National nutrition surveys
1. Food consumption survey: measures the amounts and kinds of foods people consume (using
diet histories), estimates the nutrient intakes and compared them with a standard
2. Nutrition status survey: evaluates people’s nutrition status using diet histories, anthropometric
measures, physical examinations and laboratory tests
Definition of Chronic Diseases
Chronic diseases are long duration degenerative diseases characterized by deterioration of the body
organs. Examples include heart disease, cancer and diabetes.
List of leading causes of death (North America)
Disease type
1. Heart disease
2. Cancer
3. Stroke
4. Chronic lung disease
5. Accidents
6. Pneumonia and influenza
7. Diabetes mellitus (type 1&2)
8. Suicide
*Note that the top 3 diseases are diet related
Risk factors for chronic diseases
- A risk factor is a condition or behaviour associated with an elevated frequency of a disease, but
not proved to be causal
-
Risk factors for disease include overweight, cigarette smoking, alcohol abuse, high blood
pressure, high blood cholesterol, high fat diet and physical inactivity
Note that is does NOT mean that all people with the risk factor will develop the disease
However, a strong association between a risk factor and a disease means that when the factor is
present, the likelihood of developing the disease increases
Functional foods
Functional foods are products that may look like or be a conventional food and be consumed as
part of a usual diet, but have physiological benefits or can reduce the risk of chronic disease
beyond basic nutritional functions
Eg. Soy based foods. Regular consumption of foods containing soybean has been shown to
reduce the risk of developing hypertension.
Nutraceuticals
Nutraceuticals are products isolated or purified from food, generally sold in a medicinal form
not usually associated with food and have physiological benefits or provide protection against
chronic disease.
Eg. Isoflavones (phytochemical) from soybeans can be extracted and sold in pill form. Isoflavone
activities mimic those of hormones such as estrogens. (another example: fish oil extracted from
fish into pill form)
Environmental issues and nutrition
-
Ability of foods to provide a diet and a healthy environment
Environmentally friendly and green are used to describe foods that are produced with the least
amount of destruction to non-renewable resources
To be called “green”, a product must:
o be energy efficient
o be non-polluting
o make minimum use of packaging (biodegradable)
o contain no harmful substances
o where possible, be made from renewable resources
o packaging should be recyclable
o be capable of safe disposal
o not harm human health
o be made from locally obtained materials, to minimize transportation costs
o satisfy a genuine human need
Relationships among nutrition, food and the environment
1. Food and agricultural factors affecting nutrition and health:
a. Increased demand for food influenced by:
i. Population growth
ii. Urbanization (less people on farm growing food for more people on nonfarm)
iii. Food losses, wastage and spoilage
iv. Demand for high animal-protein diets
b. Increased food production is influenced by:
i. Productive land (with rich soil)
ii. Deforestation (loss of trees keep soil in place)
iii. Increased productivity
iv. Agricultural chemicals
v. Aquaculture (fish farming – growing fish on purpose as a food source)
vi. Biotechnology
vii. Animal health
viii. Animal wastes
ix. Irrigation (allow very dry unproductive land to become productive)
x. Fuel
xi. Increased exploitation of the seas
xii. Decreased food losses
c. Environmental changes that may have negative effects on food production:
i. Climate changes
ii. Ozone layer depletion
iii. Pest resistance to pesticides
iv. Resistance of pathogens to antibiotics and chemicals
v. Loss of genetic resources
vi. Soil erosion and salinization of soil and water (over irrigation)
vii. Inappropriate agricultural systems and/or technology
2. Environmental impact on nutrition and health
a. Potential health consequences of chemical contamination of food
b. Foodborne and waterborne disease from biological contamination and from irrigation
c. Non-communicable diseases associated with diet such as:
i. Malnutrition
ii. Deficiency diseases
iii. Coronary heart disease, diabetes, some cancers
June 5, 2014
TOPIC 2
FOOD PRODUCTION AND PRESERVATION
Food availability
Food security: Access by ALL people at ALL times to nutritionally adequate, safe, personally acceptable
foods from normal food channels
Food insecurity: Limited or uncertain access to foods of sufficient quality or quantity to sustain a healthy
and active life
- Risk factors for food insecurity: anything that limits resources available for food acquisition, such
as an increase in non-food expenditures, under employment and poverty
- Food insecurity leads to hunger
o Hunger is a major health issue
Food poverty: hunger occurring when enough food exists in an area, but some of the people cannot
obtain it because they lack money
- It could also be because the people are being deprived for political reasons, live in a country at
war, or suffer from other problems such as lack of transportation
In addition to hunger, other nutrition consequences of food insecurity are:
- Low birth-weight babies
- Iron deficiency
- Rickets from vitamin D deficiency (vitamin D is known as the anti-ricketic factor)
Programs aimed at preventing or relieving malnutrition
1. Food stamps (in the USA) (under nutrition)
o Provides assistance to over 17 million people at a cost over 15 billion per year
o More than half of the recipients are children
o Food stamps can be used like cash to purchase food and food-bearing plants and seeds
o Cannot be used to buy tobacco, cleaning items, alcohol or other non-food items
2. National food recovery: involves collection of wholesome foods for distribution to low-income
people who are hungry
Four common methods of food recovery are:
o Field gleaning: collecting crops from fields that either have already been harvested or
are not profitable to harvest
o Perishable food rescue or salvage: collecting perishable produce from wholesalers and
markets
o Prepared food rescue: collecting prepared foods from commercial kitchens
o
Non-perishable food collection: collecting processed foods from wholesaler and markets
(canned goods, etc)
3. Local efforts: food recovery programs depend on volunteers. Concerned citizens work through
local agencies and churches to feed the hungry
Community-based food pantries provide groceries, and soup kitchens serve prepared meals
The 4 Pillars of Food Security
1. Availability: Sufficient amount at all times, and variety at a reasonable cost
o This is affected by time of year/season, civil conflict/war, food preservation and supply
2. Accessibility: determined by entitlements (the bundle of resources needed to acquire food)
o Accessibility (access) is affected by:
i. Market prices
ii. Employment/funds ($)
iii. Production and marketing systems
iv. Gender and power relations within the household
v. Education
vi. Transportation
vii. Water
viii. Sanitation
3. Adequacy: provide nourishment
o Affected by: control over resources, nutrient content of the food/quality, information
about food/nutrition
4. Acceptability: refers to food that is:
o Personally palatable
o Acquired by a socially-acceptable means of obtaining food (not stealing the food)
o Culturally appropriate
Food Production
Methods of increasing food productivity
1. Agricultural Chemicals:
o Fertilizers and pesticides increase crop yield and quality when applied appropriately
2. Aquaculture: Practice of mass production of fish in ponds or in floating cages in rivers, lakes or
sea
With aquaculture, food safety concerns include:
o Exposure to chemical pollution and oil spills
o Residual levels of drugs and medications in the flesh of the fish. Drugs and medications
are required to prevent spread of diseases in such dense fish populations
3. Biotechnology
o Genetic engineering: manipulation of the genetic material of living organisms
o Biotechnology is the practice of genetic engineering to make useful biological products
o
Genetic engineering has been used to:
i. Improve resistance of food crops to pest infestation
ii. Increase crop yield
iii. Extend shelf life of some foods
iv. Improve food texture
Typical examples of genetic engineering:
o Delayed ripening in tomatoes
o Chymosin or rennin (an enzyme) used for cheese making
o Round-up technology that confers herbicide resistance on certain crops like canola and
soybean
o Bovine somatotropin hormone (BST). Also called bovine growth hormone. Improves milk
production in cows by 10-14%. BST is NOT approved for use in Canada
Plant and animals modified by genetic engineering are called transgenic.
4. Irrigation
o Involves providing water to crops
o Helps provide a wide variety of food that would otherwise be less available
o Adding moisture to soil to grow better quality and quantity crops
Food production and the environment
Producing food has always cost the earth dearly:
- Land clearly causes loss of wetlands, forests, wildlife and native ecosystems
- Use of fertilizers, herbicides and pesticides can pollute the water, kill plants and insects, and
cause resistant pests and weeds to evolve
- Irrigations adds salt to the soil and depletes ground water
- There is a continuous decline in species diversity. It is estimated that 140 species of plants and
animals go extinct per day
- Animal wastes from raising livestock in concentrated areas (feedlots or hog farms) adds to water
pollution
- The food industry has a high rate of energy consumption leading to increased burning of fossil
fuels
The alternative is sustainable agriculture which is defined as:
“The use of practices that minimize technological, fuel and chemical inputs and match the local
conditions or needs of an area.”
Examples of sustainable agricultural practices are:
o Integrated pest management – the use of two or more techniques such as crop rotation
and natural predators (rather than pesticides) to control pests
o Use of manure to decrease need for chemical fertilizers
o Plowing of compost back into the soil to increase its water holding capacity
o Open range grazing
Environmental problems limiting food production
1. Soil erosion and salinization (a by-product of irrigation), which result in excessive loss of
croplands
2. Deforestation which leads to soil erosion
3. Air pollution produced from burning of fossil fuels, which damages crops and depletes the ozone
(allows sun rays to come through and damage crops)
4. Ozone depletion, which allows harmful radiation from the sun to damage crops, especially
radiation-sensitive crops such as soybeans, the world’s leading protein crop
5. Overfishing and water pollution, which are destroying fisheries and diminishing the supply of
seafood
6. Climate changes, which are caused by increased atmospheric concentrations of heat-trapping
carbon dioxide produced by fossil fuels
7. Water scarcity. In some areas there is not enough fresh water to support survival of crops,
livestock and people
8. Extensive overgrazing, which is causing deterioration of the rangelands
Biodiversity
- Refers to the variety and variability of living organisms and their ecosystems
- Biodiversity includes diversity within species (genetic diversity), among species and among
ecosystems.
- Decrease in biodiversity began with the “Green Revolution” – the dramatic increase in food
production in the 1960’s due to new seeds developed from crossbreeding
o The new seeds were resistant to insects and disease and yielded millions of tons of extra
grain
o Insects and viruses were able to mutate, overcoming the protection of these plants
o Scientists were forced to search for new genetic codes, resulting in crops that are
genetically uniform
o Net result is the extinction of many plant species and decrease in biodiversity
Why plants disappear
1. Inability to adapt to climate changes
2. Loss of forests or harvesting of forest resources
3. Severe soil erosion by wind or heavy rains or soil pollution by repetitive use of chemical
fertilizers
4. Market pressure on farmers to switch to commercial production of single varieties
Why should we care?
- Plants provide the essentials of life: food, clothing and medicine
- Different plants have different characteristics which are determined by their genes. When a
plant species vanishes, so do its genes
- As the plant gene pool shrinks, so do our options for food and medicine
Eg. Of the 5,000 food plants grown throughout the world a few centuries ago, only 150 are
cultivated in commercial agriculture today
June 6, 2014
Food Preservation
- Foods spoil because of microbiological, chemical, physical or enzyme-induced decay.
- Decrease in food losses is achieved mainly by food preservation and food additives.
There are 3 main classes of food preservation:
1. Physical: drying, heating, cooling, irradiation and blanching
2. Chemical: addition of sugar, salt or chemical preservatives
3. Biological: fermentation (using living organisms to preserve food)
Drying: involves removal of water from foods
- The food is preserved because microorganisms cannot survive in a dry environment
- In ancient times drying was done predominantly by the sun
- Currently the food industry uses oven drying, spray drying and freeze-drying
- A problem with drying by heat is the loss of heat-sensitive nutrients such as vitamin C, riboflavin
and niacin
Canning
- Kills harmful or spoilage-causing microbes and their spores
- Heat must be controlled to kill harmful microbes without damage to nutrient quality
- Water-soluble vitamins may be lost when food is canned in water, especially if the water is
discarded before the food is consumed
- Low canning temperatures and improper seals on canning jars may allow growth of Clostridium
botulinum which causes deadly botulism poisoning
Refrigeration and freezing
- Involves cooling of food to temperature levels that prevent growth of microbes
- Excellent for maintaining the sensory qualities and nutritive value of foods
- When meat is thawed, some vitamins and minerals may be lost in the drippings
- Some microbes such as Listeria can grow at refrigeration temperatures. (Listeria is very
dangerous for pregnant women)
- Refrigeration does not prevent the growth of molds (fungi)
Pasteurization
- Heating foods to a specified high temperature (80-90C) for a short time kills most diseasecausing microbes and their spores
- Pasteurized food is not sterile, so it must be refrigerated or preserved by other means
- Pasteurization of milk and fruit juices results in considerable loss of vitamin C
- However, there are no adverse nutrition implications. Milk is low in vitamin C, while the amount
remaining in pasteurized orange juice will provide the recommended daily intake
Sterilization
- Complete destruction of microorganisms
- The food is exposed to wet heat for 15 mins at 121C
- In commercially-sterile foods all pathogenic and toxin-producing organisms, as well as spoilage
microorganisms, are destroyed
- Commercially-sterile foods have a shelf-life of 2 years
Irradiation
- Sterilization of foods by exposure to energy waves, similar to ultraviolet and microwaves
- Commonly used method involves ionizing radiation from radioisotopes
- Kills molds, insects and harmful bacteria
- All irradiated foods must carry an international symbol called the “radura”. The symbol must be
accompanied by the words “treated by irradiation” or “treated with irradiation”
- In Canada only 4 types of food products have been approved for irradiation: potatoes, onions,
wheat or whole wheat flour and spices/dehydrated seasoning preparations
Topic 3
FOOD SAFETY
- Greatest health risk from food is microbial contamination (bacteria, fungi (molds & yeasts),
parasites and viruses)
- Expert’s ranking of health hazards based on occurrences of death and illness (ranked):
1. Microbial food poisoning
2. Malnutrition
3. Environmental contaminants
4. Naturally-occurring contaminants
5. Pesticide residues
6. Intentional food additives
-
Ranking of food safety concerns:
Consumers
1. Pesticides
2. Pollutants
3. Feed ingredients
4. Veterinary drugs
5. Food additives
6. Foodborne diseases
7. Natural toxins
Scientists
1. Foodborne diseases
2. Natural toxins
3. Pollutants
4. Food additives
5. Feed ingredients
6. Veterinary drugs
7. Pesticides
Microbial food poisoning (foodborne diseases FBI)
- Approx. 11 to 13 million cases every year in Canada according to Health Canada estimates
- For every case that is reported, hundreds of cases go unreported
- Contradictory info exists on % of cases that occur in food service establishments vs. % of cases
which occur in the home; estimate only 3% of cases occur in food processing
- Canfightbac.org
Prevention of foodborne diseases:
- Use good quality ingredients and sanitary equipment or conditions
- Temperature control (keep hot foods hot and cold foods cold)
- Do not consume food that is suspicious
Foodborne illness can occur from:
1. Biological contaminants (pathogens like bacteria, viruses, parasites and fungi)
2. Chemical contaminants
3. Physical contaminants
4. Allergens
Of these, bacteria are associated with the greatest number of cases of foodborne illness and death.
6 Things Bacteria need in order to grow
Fat
Acidity or alkalinity (pH)
Time
Temperature
Oxygen (or NO oxygen)
Moisture
4 Safe Thawing Methods:
1. In refrigerator on bottom shelf
2. Under cold running water (or with ice chunks in water)
3. In microwave (cook immediately thereafter)
4. Cook from frozen (takes 50% longer)
Midterm 120 marks
45 MC – 1 mark
20 T/F
Terms and definitions – 18 marks in total
9 Long answers – 37 marks
June 9, 2014
Some of the bacteria responsible for foodborne illness:
1. Salmonella
o Found in human and animal feces
o Enters food via contaminated water, cutting boards, contaminated meat products
(usually poultry), cracked eggs and actual bits of feces on food
o Onset of symptoms = 5-72 hours, duration 1-4 days
o Typical symptoms include nausea, headache, diarrhea, abdominal pain, chills, fever,
vomiting and dehydration
o Can be fatal in infants, elderly and the sick
o Thorough cooking of foods kills salmonella
o Typical foods involved: raw or undercooked eggs, raw milk and poultry
o Prevention: cook eggs and poultry thoroughly, pasteurize milk, irradiate chicken, avoid
cross contamination
2. Staphylococcus aureus (staph aureus)
o Responsible for 20-40% of all cases of food poisoning
o Toxin the bacteria produce causes poisoning – indestructible
o Onset of symptoms = 20 mins – 6 hours, duration usually is 2-3 days
o Symptoms: nausea, vomiting, diarrhea, cramps
o Rarely fatal
o Susceptible foods: custard, ham, egg salad, potato salad, macaroni salad, seafood,
cheese, poultry, cream filled pastries, whipped butter
o
o
Contamination comes from people with colds, sore throats or infected skin cuts and
food slicers that are not thoroughly cleaned
Prevention: do not allow infected persons to prepare food; thorough heating and
cooling of food; good sanitation
3. Escherichia coli 0157:H7
o Relatively new strain of E. coli
o Onset is 12-60 hours, duration 2-9 days
o Symptoms = watery and bloody diarrhea. Can lead to kidney failure
o Mostly from raw or undercooked meat and raw milk. Also in unpasteurized fruit juices
o Known as “hamburger disease”
o Prevention = cook meat thoroughly, especially ground meat. Pasteurize milk and fruit
juices
4. Clostridium botulinum
o Anaerobic bacteria present In soil
o Produces a toxin that blocks nerve function
o It is the most powerful natural toxin
o Found in canned foods, especially low acid home canned foods (vegetables)
o Symptoms include double vision, inability to swallow, speech difficulty and progressive
paralysis resulting in death due to botulism poisoning
o Prevention – sterilize canned foods (use pressure canner); never use dented cans
Note;
-
Danger zone is 4 – 60 degree C (anything warmer than fridge temp)
Keep cold foods at or below 4C
Keep hot foods at or above 60C
Listeria monocytogenes can grow at refrigeration temps
Steps to food Safety:
1. Shopping
o Shop last during outing
o In the grocery store, buy perishable items last. Get perishable foods into the refrigerator
or freezer as soon as possible
o On a hot day, pack perishable foods in a cooler with ice packs
o Don’t buy it if you won’t use it before expiry date
o Buy foods in good condition
2. Storage
o Refrigerator temperature not higher than 4C
o Freezer temperature not higher then -18C
o Freeze meat if you can’t use it within a couple of days
o Prevent raw juices of meat from dripping on other food
3. Preparation
o Wash hands with soap and water before preparing food
o Replace dish cloths, towels and sponges often
o Avoid cross contamination
o
o
o
o
Use plastic cutting boards. Rinse cutting boards with dilute chlorine bleach and water
solution to prevent growth of food poisoning microorganisms
Thaw foods in refrigerator
Cook poultry and eggs thoroughly
When using microwave, cover, rotate, stir
4. Serving
o Use clean dishes
o Never leave perishable foods out of refrigerator for more than 2 hr
5. Handling of leftovers
o Refrigerate promptly (in small shallow dishes, using several if necessary)
o Remove stuffing from poultry, store separately
o Reheat foods adequately (at least to 74 C)
o Discard foods with past expiry dates
o If in doubt, throw it out!
o Trim at least 1 inch off surface of hard cheese where any mold has grown. Discard other
moldy foods
Traveler’s diarrhea: a type of FBI (nausea, vomiting and diarrhea) contracted while traveling
Caused by consuming food or water contaminated by any of several organisms most commonly E. coli,
shigella, campylobacter jejuni and salmonella
Why?
a) Other countries’ cleanliness standards for water and food may be lower than those in USA and
Canada
b) Traveler may not have immunity to microbes
Prevention (food safety when traveling):
1. Wash hands with soap and warm water before handling or eating food
2. Eat only cooked or canned foods. Avoid raw fruits and vegetables except if you have washed
them in boiled water or peeled them yourself
3. Skip salads, raw fish and shellfish
4. Do not use local ice or water supply, even to brush teeth
5. Drink only bottled, treated or canned beverages (without ice)
6. Take along medication based on the advice of your physician
Non Bacterial food contamination
1. Viruses
a. Hepatitis A
o Takes about 4 weeks to develop; disease lasts for 2 weeks to 6 months. May
cause jaundice
o Usual transmission is by decal-oral route with foods subject to decal
contamination due to a food handler, or contact with sewage
o Prevention:
1. Cook shellfish thoroughly
2. General sanitation
b. Norwalk virus
o First recognized in a school outbreak in Norwalk, Ohio in 1968 with water as the
suspected source
o Symptoms consist of gastroenteritis with vomiting and diarrhea
o Incubation of 1-2 days, followed by illness that lasts 12-48 hours. Often known
as the “stomach flu”
o The virus is shed in feces during the disease period
2. Mycotoxins – toxins produced by molds growing on foods
a. Best known are the ‘aflatoxins’, which can be found in nuts (especially peanuts), corn,
wheat and oil seeds
b. Prevention – difficult to avoid contamination. Therefore, health regulations permit
certain levels in foods
3. Mad cow disease (BSEinfo.ca)
a. Mad cow disease is actually Bovine spongiform encephalopathy (BSE)
b. Brain becomes riddled with holes, taking on a sponge-like consistency
c. Always leads to death of the animal
Naturally-occurring toxicants (toxins)
- Some food plants produce toxic chemicals as a form of natural defense against animals and
microbes
- No need to eliminate these foods from our diet because only small amounts are eaten in a
typical diet. Therefore, they do not present a serious health hazard
Examples of natural toxins:
1) Solanine
o Green layer that develops under the skin of potatoes
o Lethal levels can be reached when potatoes are diseased, bruised or exposed to light
o Cooking does not destroy solanine
2) Cyanogens
o Compounds that contain cyanide which can release a potent respiratory inhibitor
o Found in lima beans, fruit seeds such as apricot pits and tubers such as cassava
o Long-term consumption can lead to ataxic neuropathy, a group of nervous disorders
3) Goitrogens
o Compounds that inhibit proper utilization of iodine in the body
o Can cause enlargement of the thyroid gland (ie. Goitre, due to iodine deficiency)
o Found in cabbage and related species (broccoli, cauliflower)
4) Tannins
o Found in tea, seed coat of grains and legumes
o Form insoluble complexes with proteins resulting in inactivation of digestive enzymes
and protein insolubility
o May cause growth depression and decreased iron absorption (prevents o2 from getting
to cells)
o Other effects include increased excretion of minerals and proteins
5) Phytate
o Found in cereal grains, legumes (beans, peas, lentils), some roots and tubers
o Forms complexes with mineral ions and proteins, decreasing their bioavailability
(becomes unavailable to work in life processes)
o Forms complexes with digestive enzymes such as trypsin and pepsin, resulting in
decreased digestion of food
6) Oxalates
o Found in spinach
o Binds calcium so excessive levels of oxalic acid could lead to loss of calcium from bones
(bones become hallow, fragile and very weak)
o May result in chronic disease such as kidney damage and formation of kidney stones
7) Saponins
o Have similar properties to soaps
o Occur in a wide variety of legumes and cereals, particularly high content present in the
seed coat of quinoa
o Not destroyed by cooking, but can be hydrolyzed during fermentation
o Major effect is hemolysis of red blood cells; may cause growth inhibition (breaking down
red blood cells)
8) Lectins = proteins that are attracted to certain sugar molecules
o They are hemagglutinins, ie they cause agglutination (clumping) of red blood cells
o Lectins are highly toxic to humans animals, but are destroyed by heat used in traditional
cooking
o Binding of lectins reduces ability of cells to absorb nutrients from the GI tract, which
leads to growth retardation and in extreme cases, death
9) Enzyme inhibitors
o Certain compounds in plants inhibit activity of trypsin, chymotrypsin and amylase
o Cause growth inhibition by interfering with protein digestion (so used as a component
of some anti-AIDS drug cocktails)
o Other symptoms include excessive secretion of pancreatic enzymes leading to
pancreatic hypertrophy
o Can be destroyed by adequate heat and fermentation
10) Nitrates
o Found in spinach, lettuce and beets
o Can be converted into the carcinogen, nitrosamine
11) Marine toxins
o Paralytic shellfish poisoning (disease) caused by consumption of mussels, clams and
oysters, especially the dark meat
i. Caused by a toxin called saxitoxin
o
Ciguatera caused by consuming contaminated tropical herbivorous reef fish such as
grouper and red snapper
i. Causes hot/cold inversion
o
Neurotoxic shellfish poisoning
i. Caused by consumption of clams and oysters that contain brevitoxins
o
Amnesic shellfish poisoning
i. If mussels from the eastern shore of Canada are infected with a microorganism
called Nitschia, a toxin called domoic acid is produced
ii. Symptoms include irreversible short-term memory loss and disorientation
Toxicants produced during food processing
1) Browning products
o Found in roasted grains, baking bread
o Can cause DNA mutations which could lead to cancer formation
2) Ethyl Carbamate
o A recognized cancer-causing agent produced during fermentation of some foods like
Japanese soy sauces
Environmental Contaminants/Pollutants
- Include industrial pollutants, toxic metals and contaminants from packaging
- Routine monitoring of chemical contaminants is carried out and a ban is imposed if levels are
too high
1) Heavy metals
o Lead
o Mercury
o Cadmium
o Selenium
o Arsenic
-
Mercury
Naturally occurring element in soils, rocks, lakes, streams and oceans
High amounts of mercury can damage the nervous system of people and animals
Accumulates in the food chain so that predatory species have higher levels of = bioaccumulation
CFIA (Canadian food inspection agency) regularly tests commercial fish and shellfish to ensure
that the Canadian guideline for mercury in fish is not exceeded
Most marine fish are well below the limit, except swordfish, shark, or fresh and frozen tuna
Limit consumption of these to one meal per week (does no apply to canned tuna)
For young children and pregnant women this should be limited to one meal per month
2) Halogens and organic halogens
o Chlorine
o Iodine
o Vinyl chloride
o Ethylene dichloride
o Trichloroethylene
o Polybrominated biphenyl (PBB)
o Polychlorinated biphenyls (PCBs)
Food Packaging Materials
- Food manufacturer/seller bears a legal responsibility for safety of packaging materials used, due
to potential migration of chemicals from packaging materials to foods
- Manufacturers must submit data on: chemical composition, intended end use, extractability of
chemicals by food, toxicological data on residues
- Regulations exist for some packing materials with levels permitted and migration limits
Food Additives
Substances not normally consumed as foods but added to food either intentionally or by accident
Purpose:
- To provide leavening or control acidity/alkalinity
- To enhance flavour or impart desired colour
- To improve or maintain nutritional quality of foods
- To maintain product consistency
- To maintain palatability and wholesomeness
Food additives do not include:
- Agricultural chemical residues
- Food packaging materials
- Veterinary drugs
Regulations specify:
- Purpose
- Additives that can used for specific purposes
- The foods in which they are permitted
- The amount that is permitted
Criteria for food additives:
- Must be safe for continued use
- Must not lead to deception
- Must be an advantage to consumer
7 safety evaluation studies or food additives:
1) Acute studies (short term)
2) Sub chronic, dose range finding studies (medium)
3) Absorption, distribution, metabolism and elimination studies (digestion)
4) Chronic studies (long term)
5) Carcinogenic and mutagenic studies – ie. The Ames test
6) Reproductive and teratogenic studies
7) Neurotoxicity studies
Direct Food Additives
1) Anticaking agents
o Absorb moisture and in the process prevent foods from getting “wet”
o Used in table salt, baking powder and other powdered food products
o Ex. Calcium silicate, baking powder
2) Antioxidants
o Prevent discolouration of foods
o Prevent fats (eg. In salad dressings) from turning rancid
o Eg. Vitamin C, butylated hydroxyanisole (BHA) and butylated hydroxytoluene (BHT)
3) Emulsifiers
o Facilitate distribution and suspension of fat in water or vice versa
o Used in the manufacture of chocolates, margarine, cake mixes, potato chips, salad
dressings
o Eg. Lecithin (extracted from egg yolk), soy lecithin
4) Humectants
o Help retain proper moisture, flavour and texture of foods
o Used in candies, shredded coconut and marshmallows
o Eg. Glycerol
5) Antimicrobial agents
o Preservatives that prevent microorganisms from growing
i. Sugar (in jams and jellies) and salt are the most widely used to preserve meat
and fish
o Sugar and salt capture water in food, making it unavailable to microbes
ii. Potassium sorbate and sodium propionate are used to extend the shelf life of
baked goods, cheeses, beverages, mayonnaise, margarine
iii. Nitrates and nitrites are used to:
o Preserve colour, especially the pink colour of hot dogs
o Prevent the growth of bacteria, especially those that produce the
deadly botulism toxin
6) Flavour enhancers
o Used to enhance flavour of foods
o Eg. Monosodium glutamate (MSG) and hydrolyzed vegetable proteins
o In Canada, MSG is considered an ingredient (not an additive) and it must be declared on
the label. Not allowed in foods for infants
o Non-nutritive sweeteners (aspartame)
7) Nutrient additives
o Added to fortify or maintain nutritional quality of foods
o Eg. Iodine added to salt, vitamins A and D added to milk, folic acid and other B vitamins
added to breakfast cereals
8) Food colours
o Artificial colour additives include blue, green, red and yellow
o Natural colour additives include:
i. Caramel that tints the colour of cola beverages and baked goods
ii. Vegetable colours like (yellow) carotenoids that colour margarine, cheeses and
pastas
Indirect (incidental) food additives
Find their way into foods during harvesting, production, processing, storage or packaging
- Dioxins
o Found in coffee filters, milk cartons, paper plates and frozen food packages
o Contamination occurs only in trace quantities that appear to pose no health risk to
humans
- Methylene chloride
o Used to remove caffeine in the production of decaffeinated tea or coffee
o Traces are left in the decaffeinated product, but pose no significant health hazard
- Antibiotics (veterinary drugs)
o Animals raised with antibiotics could have residues in meats and milk. Sensitive people
could suffer allergic reactions
o Regulations specify withdrawal periods between day medication is used and slaughter
to allow for drug metabolism and excretion
Food Allergy = an immune response to a food substance
Food allergens (aka antigens) are proteins foreign to the body that elicit production of antibodies (large
immune cells that are produced to inactivate the antigens).
90% of food allergies are caused by nuts, eggs, milk, wheat and shell fish. Lab tests are required to
identify true allergies.
Breastfed babies are at lesser risk of developing allergies when compared to formula fed infants.
Food Allergies: Myth vs Fact
- Myth. Lots of people have food allergies
Fact. Surveys show that 1 in 3 people believe they are allergic to some foods, but in reality only 2-4%
of the US population and 7% of Canadians have allergies to foods
- Myth. Good allergy means runny nose
Fact. Allergic reactions can range from runny nose and asthma, to rash to anaphylactic shock
- Myth. People are allergic to food additives
Fact. Many additives such as aspartame and food dyes have been studied extensively and there is no
evidence of any true allergic reactions
However, sulfites have been shown to trigger asthma and hives
Food intolerance = an adverse reaction to a food that does not involve an immune response (or
production of antibodies)
Eg. Lactose intolerance = caused by insufficient amounts of the lactase enzyme needed to digest lactose
The undigested lactose is fermented by bacteria in the large intestine and triggers nausea, vomiting,
diarrhea when milk or milk products are consumed
June 11, 2014
Reactions often confused with food allergies:
1. Reactions to molds or other contaminants
2. Reactions to MSG (no scientific evidence of allergic effect)
3. Food poisoning
4. Reactions to natural chemicals
5. Symptoms of disease (eg. Ulcers)
6. Enzyme deficiencies (eg. Lactose intolerance)
7. Psychological reactions
Food Labelling
Health claims: any claim on a food label that relates a substance to a disease or health-related condition
(eg. Calcium and osteoporosis)
A food label must contain:
- Nutrition facts label including:
o Serving size
o Amount per serving of each nutrient (except vitamins and minerals)
o Amount of each nutrient (except sugars and protein) as a percent of Daily Value for a
2,000 kcal diet
-
General product labelling such as:
o Product name and place of business
o Product net weight
o Product ingredient contents (in decreasing order of amount by weight)
o Company name and address
o Product code (UPC bar code)
o Product date if applicable
o Religious symbols if applicable
o Safe food handling instructions if applicable
o Special warning instructions if applicable (eg. Aspartame is destroyed by heating)
Organically grown food
1. Organically grown crops are grown and processed without the use of synthetic fertilizers,
pesticides, preservatives and other chemical ingredients
2. Meat and dairy products may also be called organic if the livestock has been raised on organic
feed, without use of hormones and antibiotics
-
Producers may not claim products are organic if they have been irradiated, genetically
engineered or grown with fertilizer made from sewer sludge
Organic food products are usually more expensive, but offer no nutritional advantage
Not necessarily healthier (eg. Use of unprocessed manure may transmit bacteria such as E. coli
to organic foods)
A challenge in organic farming is “nutrient mining” (nutrients are removed from the soil in the
form of crops; impossible to replace all nutrients with livestock manure and compost)
Regulating Food Safety
1. Canadian Food Inspection Agency (CFIA)
o Reports to Minister of Agriculture
o Provides all inspection services related to: food safety, economic fraud, trade related
requirements, animal and health programs
CFIA responsibilities:
a. Control animal diseases and pests
i. Stop diseases/pests from entering Canada, control or eradicate diseases if they
do occur, quarantine animals and inspect farmers’ fields and imported plants
b. Inspect Foods – register and inspect all food processing plants, monitor imported foods
c. Prevent Fraud – enforce labelling laws, check quantities, verify composition and grade
d. Regulate seed, feed and fertilizers
e. Diagnose problems
i. Identify problems in food products
ii. Develop rapid methods for detecting food pathogens
f. Enforce safety standards
i. Work with provincial and municipal inspectors
2. Health Canada has responsibility for:
o Food safety policy
o Standards setting
o Risk assessment
o Analytical testing research audit
HACCP – Hazard Analysis Critical Control Points
- Initially developed in the USA to ensure safety of foods to be used in the space programs
- It is a preventive system that significantly reduces production of unsafe products
HACCP was designed for 3 reasons:
1. Identify hazards that could occur in foods during their preparation
2. Identify control points in food production that ensure a safe product
3. Monitor these points/steps to ensure they are being controlled
HACCP system consists of 7 principles:
1. Conduct a hazard analysis
2. Determine critical control points
3. Establish critical limits
4. Establish monitoring procedures
5. Establish corrective actions
6. Establish verification procedures
7. Establish record-keeping and documentation procedures
June 12, 2014
Topic 4 – FOOD CHOICES
Why do we choose foods?
- Personal preference
- Habit
- Ethnic heritage or tradition
- Social interactions
- Availability, convenience and economy
- Positive and negative associations
- Emotional comfort
- Values
- Body weight and image
- Nutrition
Food available for consumption – 2009
On a per capita basis, the Canadian diet in 2009 includes more fresh fruit and vegetables, cereals, coffee
and fish compared with 2008 (increase in consumption of fruits and veggies)
The total daily intake of calories per person fell to 2 357.8 calories, down 155.6 calories from the peak in
2001
Total fresh fruit intake, including citrus, reached a record 39.3 kg per person, up slightly from 2008
The total fresh vegetable intake, excluding potatoes, reached a record 40.7 kg per person in 2009,
slightly higher than the 5 year average of 38.6 kg per person. This was just above the previous record of
40.3 kg in 2001
Per capita red meat available for consumption continued to decline in 2009, falling by 0.7% to 23.4%...
In the past two decades, Canadians have shifted towards a diet which includes more fruits and veggies,
cereal products and nuts and beans
During this time, poultry consumption has increased while beef and pork consumption has continued to
decline
Oil and fat consumption increased through the 1990s to a peak in 1998, but has since fallen steadily
Sugar available for consumption has increased over the past two years from the record low set in 2007
Data on food availability have been adjusted to account for losses in cooking, storage and waste that
occur in homes, restaurants and institutions while preparing and processing food
Food Consumption trends:
(Courtesy: Dr. Diane Morris, Mainstream Nutrition)
1. Dichotomous dining
o Dual approach to eating
o Consumers demand low fat healthy foods but crave high fat sweets and treats
o Food industry has responded by increasing the number of products bearing a low fat
label in addition to increase in the number of new products developed in the dessert
category
2. Quilt cuisine
o Increase demand for unique tastes of ethnic foods and exotic spices/ingredients
3. Speed and feed (dashboard dining)
o Trend where consumers routinely circle through fast food restaurants for their meals
4. Speed scratch cooking
o Home-cooked meals put together with little time and effort, using premixed products
that can be cooked quickly
5. Five-a-day
o Most consumers eat several small meals throughout the day
o This has changed the concept of ‘meals’ and ‘snacks’
Types of eating styles:
1. Night eater
Eating style/attitude towards food (ES/ATF)
o Wakes up in the middle of night and raid refrigerator or eat just before going to bed
Other characteristics (OC)
o Usually don’t eat 3 balanced meals a day
o Often skip breakfast or lunch
o Have stressful lives
o May also be heavy smokers
o Big coffee drinkers
2. Compulsive eater/eating addict
ES/ATF
o Use food to block out dears or as substitute for love
o Eat constantly often until they are sick
o Some are closet eaters
o Rarely sit down to an entire meal
OC
o Children who are obese during development often become overeaters
3. Liquid drinker
ES/ATF
o Drinks lots of coffee, soft drinks and or alcohol
o Get most calories from liquids
o
Diets low in essential nutrients and fibre
o
o
o
Workaholics
Under stress
Can be addicted to some fluids
OC
4. Traditional overeater
ES/ATF
o Trained to eat 3 meals a day in addition to snacks
o Food represents security, family love
o May encounter opposition from family if they try to change eating habits
OC
o 15% of obese people are traditional overeaters
5. Environmental eater
ES/ATF
o Adverts, parties, luncheons, sight and smell of food trigger an eating episode
o Eat because the food is available
o Although impulse eater, they usually have regular meals
OC
o Tend to be executives, shift workers or working women
o Have active business, social and community schedules
6. Gastronomic overeater
ES/ATF
o Love to cook
o More concerned with food quality than calories
o Eat because food gives them pleasure
o Seldom eat large quantities or have food between meal snacks
OC
o High percentage is male
o Often professionals with middle to high income who are single or divorced
7. Snacker
ES/ATF
o Become overweight due to ignorance or indifference to nutrition
o Never eat real meals
o Prefer to snack on foods they enjoy
o Likely to try fad diets and pills
OC
o Anyone with a sedentary lifestyle
o Can happen to athletes once their career is over
8. Convalescent overeater
ES/ATF
o Sudden lack of exercise with no reduction in calories leads to weight gain
o Use food to relieve boredom, frustration and depression during convalescence
OC
o
Almost 2/3 of those recovering from accident, surgery or illness
9. Chronic dieter
ES/ATF
o Know everything about dieting but cannot lose weight
o Have tried it all
o Usually looking for instant results
OC
o Usually women in their late 30’s and early 40’s
Eating Disorders
- Three square meals a day, an occasional snack or missed meal, and caloric intakes that match
the body’s need for calories. This set of practices is considered “orderly” eating
- Self-imposed semi-starvation, feast and famine cycles, binge eating, purging, and regular
consumption of non-food substances such as paint chips and clay. These behaviours are
symptoms of disordered eating
- Eating disorders are much more common in females than males
1. Anorexia nervosa
o An eating disorder characterized by extreme weight loss, poor body image, and
irrational fears of weight gain and obesity
o Refusal to maintain weight that is over the lowest weight considered normal for age and
height. They starve themselves of food
o Intense fear of gaining weight or becoming fat, even though underweight
o They become cold easily and have unusually low heart rates, dry skin, low blood
pressure, absent or irregular menstrual cycles, infertility and poor pregnancy outcomes
o One out of ten anorexic people starve themselves to death
2. Bulimia nervosa
o An eating disorder characterized by recurrent episodes of rapid, uncontrolled eating of
large amounts of food in a short period of time (binge eating)
o Episodes of binge eating are often followed by purging. Minimum average of two binge
eating episodes a week for at least 3 months
o A feeling of lack of control over eating during the binges
o Regular use of one or more of the following to prevent weight gain:
 Self-induced vomiting, use of laxatives or diuretics, strict dieting or fasting, or
vigorous exercise persistent with over-concern with body weight and shape
3. Binge eating disorder
o An eating disorder characterized by periodic binge eating, which normally is not
followed by vomiting or the use of laxatives
o Must experience eating binges twice a week on average over a period of six months to
qualify for the diagnosis
o People with this condition tend to be overweight or obese, and one third are male
o Stress, depression, anger, anxiety, and other negative emotions appear to prompt binge
eating episodes
4. Pica = regular consumption of non-food substances such as clay or laundry starch. It is not clear
why pica exists
Young children and pregnant women are most likely to engage in the practice for unknown
reasons, it rarely occurs in men
Pica most commonly takes the form of:
a. Geophagia (clay or dirt eating)
b. Pagophagia (ice eating)
c. Amylophagia (laundry starch or common starch eating)
d. Plumbism (lead eating usually from paint flakes)
a. Clay and dirt consumption can block the intestinal tract and cause parasitic and bacterial
infections. Also associated with iron-deficiency anemia in some individual.
b. Ice eating may be common during pregnancy. In a study of women from low-income
households in Texas, 54% of pregnant women reported eating large amounts of ice
regularly
The ice eaters had poorer iron status than other pregnant women who did not eat ice
c. The sweet taste and crunchy texture of flaked laundry starch are attractive to a small
number or women, especially during pregnancy
Cornstarch may be used if the preferred laundry starch is not available. The starch may
contain contaminants because it is not intended for consumption
d. The regular consumption of sweet tasting lead-based paint chips from old houses is a
major cause of lead poisoning in young children
June 16, 2014
Sensory Factors
- Taste is determined by both taste buds and smell receptors
- Taste buds are tiny receptor organs buried in the surface of the tongue, or in the lining of the
mouth and back of throat
- Taste buds only recognize 5 sensations: sweet, salty, sour,bitter and umami. All other ‘tastes’
are really smelled
- Smell receptors in the nose are attached to nerves that enter the brain and report on the
aromas and odours of food
- Aromas are a combination of a number of smell sensations, and the brain assembles the
combination of scent signals and refers to the memory bank for interpretation
- Temperature can also influence taste and aroma and many tastes can be interactive
- Texture also enters in the perception of “taste”
- How food looks (colour), feels (mouth feel) and even sound (crunchy) can be a part of the taste
sensation
- Tastes are perceived only when the ‘taste’ chemicals are dissolved in liquids (ie saliva)
- Taste and perception of texture may cause the release of more saliva (dry food or acid that
needs to be diluted)
Sensory evaluation of foods
- Sensory properties often determine the acceptance of rejection of foods
- There are 5 classes of stimuli related to food:
o Appearance (colour, shape, form, texture)
o Odour (smell)
o Taste (sweet, sour, salty, bitter, umami)
o Sound (crackling, fizzing, bubbling, popping)
o Texture (or touch):
 Temperature (hot, cold, warm)
 Mechanical – firmness, viscosity, hardness, chewiness
 Geometrical – particle size and shape (smooth, gritty, chalky, grainy, lumpy) and
particle size and orientation (flaky, pulpy, etc)
 Mouth feel – juiciness, greasy, oiliness
Sensory evaluation: a multidisciplinary science that uses humans to measure the acceptability
and sensory properties of food and other materials
Why use sensory evaluation?
o To determine consumer acceptability
o To determine if product reformation results in a perceived difference
o To identify taint contamination and determine source of contamination
o Necessary to determine end-product quality
o Necessary to establish product specifications for quality assurance programs
o Necessary to establish shelf-life of products
Sensory evaluation techniques
a) Subjective test methods
o Uses humans to measure opinion about or an ‘emotional’ reaction to a product
o Measure how much you like a product (its acceptability_ or your preference for one
product over another
o Less reproducible
Examples of subjective test methods:
1. Triangle test: participants are given 3 coded samples and told to choose the sample that is most
different. 2 of the samples are usually the same (only researcher knows)
A or B or A’
311/565/971
2. Duo-trio test: 1 reference sample and 2 test samples. Choose the test sample that matches the
reference sample
A
B or A
Ref
565/971
3. Paired comparison: participants are given 2 samples and have to choose one that has the
highest attribute. Eg. Which of the 2 samples is sweeter
B or A
565/971
All sensory tests require controlled conditions:
o Standardized samples (size, quantity must be the same)
o Minimized distractions
o Air conditioning
o Comfortable seating
o Proper lighting
b) Objective test methods
o Measure the presence and/or intensity of specific attributes in the product using a test
equipment
o These tests are free of personal bias and are reproducible
o Eg. A colour meter can be used to determine colour of a food product
June 17, 2014
TOPIC 5 – CHEMISTRY OF FOODS
Water
- Water is an essential nutrient. We can survive for 60 days without food, but without water
death occurs within 4 days
- In the body, water becomes the fluid in which all life processes occur
- Every cell contains fluid of the exact composition that is best for that cell (intracellular fluid) and
is bathed externally in another such fluid (interstitial fluid)
- Water constitutes about 60% of an adults body weight and a higher percentage of a child’s
- Water makes up 75% of the weight of lean tissue and less than 25% of the weight of fat
- Therefore, proportion of water is generally smaller in females, obese people and the elderly
because of their smaller proportion of lean tissue
Functions of water in the body
1. Carries nutrients and waste product throughout the body
2. Maintains the structure of large molecules such as proteins and glycogen
3. Participates in metabolic reactions
4. Serves as the solvent for minerals, vitamins, amino acids, glucose and many other small
molecules
5. Acts as a lubricant and cushion around joints and inside the eye, the spinal cord and, in
pregnancy, the amniotic sac surrounding the fetus in the womb
6. Aids in the regulation of body temperature
7. Maintains blood volume
Role of water in foods
- Found in high levels in some foods, eg. Lettuce (98%), celery (95%), carrots (88%), whole milk
(88%), ice cream (61%), ham (53%)
- Moderate to low levels, eg. French fries (38%), white bread (37%), popcorn (4%), peanuts (2%)
- Much of the water in plant and animal tissues is held inside the cells (intracellular)
- In many cases water is held within the cell as a hydrate which means it does not flow from the
cell when the tissue is cut or torn
- Ability of food to hold water in this way is called its “water holding capacity”
- Some water in foods is held extremely tightly and is called “bound water”
-
-
Bound water becomes part of the structure of large molecules such as proteins and
carbohydrates and no longer has the same properties as free water
The more water that is bound, the less activity of the water. “Water activity” (Aw) is the amount
of free water available in a food
The perishability of a food is related to its water activity
Water activity is reported on a scale of – to 1. Fresh meat, fruit and vegetables have Aw of 0.951. Dried meat and vegetables have Aw of 0.2-0.4
Most bacteria cannot grow below Aw of 0.9, yeast – 0.85, molds – 0.7
Decreasing the Aw to increase shelf life of a food can be done by physically removing the water
(dehydration), addition of solutes (sugar, salt) which tie up water (eg. In jam) or by adding
humectants to absorb excess moisture
Water is also critical in microwave heating of food. It is the water molecules that respond to the
microwave energy
The energy causes water molecules to oscillate, thereby causing friction which creates heat
Microwaves penetrate the first 2-3 cm of the food. The remainder of the food is heated by
conduction (molecule to molecule). Microwaves do not heat foods from the inside out
Role of water in food preparation
1. Water is an important solvent
o Many flavour molecules are dissolved in water, eg. Coffee, tea
o Sugars are dissolved in water, eg. Fruit juices, syrups
o Starch granules are first dispersed in water and then the mixture is heated. The starch
granules absorb water to produce a thickened pudding or sauce
2. Water is used as a cooking medium (boiling and steaming)
3. Water is used as a cleaning agent for food and equipment. Removes soil, residues and
microorganisms depending on the rigour used in washing
4. Water promotes certain chemical changes, eg. Activation of chemical leavening agents (baking
powder, baking soda). Left dry these agents do not react. When water is added, carbon dioxide
is released which leavens products such as cakes, muffins
5. Water is part of the chemical reaction known as hydrolysis
o This refers to breaking of chemical linkages between units of large or complex molecules
to yield smaller molecules
o During hydrolysis, water becomes part of these smaller molecules
o Eg. When starch undergoes hydrolysis to form simple sugars such as glucose
Water in food processing
Concerned with 3 aspects of water technology:
1. Microbiological and chemical purity
2. Impurities that affect suitability for use
3. Contamination load after use (cost and difficulty of disposing of waste water)
-
Water entering a food plant must meet same health standards as for drinking water (potable)
Water may receive in-plant treatment to deal with off-flavours and odours
If contamination loads exceed regulated levels, then food processing plants are required to
adopt their own waste treatment systems
Chemicals found in water (depends on source):
1. Calcium and other minerals from rocks and soil – provides a dietary source of minerals, but may
make water “hard”
2. Fluoride may be added. Important in teeth and bone formation
3. Chlorine is often added to kill harmful microorganisms
4. Nitrates may be present – from fertilizers, manure and sewage
5. Lead may be found – from old lead pipes (no longer permitted)
6. Organic chemicals, eg. Pesticide contamination
7. High levels of microorganisms from animal or human waste resulting in cholera, dysentery,
typhoid
Is bottled water safer than tap water?
- Depends what tap water and what bottled water you are talking about
- 25% of bottled water in the USA is processed tap water which does not make it safer, healthier
or purer than tap water
- Some bottled water has high levels of sodium and does not have fluoride. Read the label
Brita filtration system:
- Reduces lead, copper, zinc, chlorine
- Has bacteriostatic effects
- Does not remove fluoride
Water Hardness:
- Presence of mineral salts determines water hardness
- Temporarily hard water – can be softened by boiling during which minerals such as calcium,
magnesium and iron precipitate out
- Permanently hard water – cannot be softened by boiling because the minerals are not
precipitated by heat
- Permanently hard water can be softened by exchanging sodium ions for the calcium and
magnesium ions (results in very high levels of sodium)
- Hardness causes scale build up on equipment and pipes
- Hard water is usually alkaline – can affect plant pigments when cooking vegetables (eg. Red
cabbage can turn green when boiled in hard water)
Carbohydrates (CHO)
- Includes sugars, starches and fibres
- Consists of carbon (C), hydrogen (H), and oxygen (O)
- Formed in green plants through photosynthesis whereby the sun’s energy converts carbon
dioxide from the atmosphere and water from the soil into glucose – simplest form of sugar
(C6H1206)
- Oxygen is given off by the plant during this process
Carbohydrate foods include:
1. Cereal grains and flours, eg. Wheat, rye, corn, rice
2. Legumes, eg. Peas, beans and lentils
3. Starchy roots or tubers, eg. Potatoes, yams, cassava
4. Fruits, eg. Oranges, apple, bananas
5. Sugars, honey, jams, molasses
Carbohydrates are classified according to the number of basic sugar (saccharide) units:
1. Monosaccharides – simple sugars, 1 unit
2. Disaccharides – simple sugars, 2 units
3. Oligosaccharides – simple sugars, 3-10 units
4. Polysaccharides – complex sugars, many units
Monosaccharides
- Includes 6 carbon hexoses and 5 carbon pentoses
- Hexose sugars such as glucose, mannose, fructose(fruit sugar) and galactose are building blocks
of starches
- Pentose sugars such as ribose, xylose and arabinose are the building blocks of fibres and gums
GLUCOSE:
- Glucose is the most abundant sugar in the world
- Found in fruits, plant juices and honey
- Often present with other sugars, eg. In honey with fructose
- Glucose is the form of sugar that circulates in the bloodstream. It is broken down in the body to
give 3 products: energy, water and carbon dioxide
- Many complex carbohydrates such as starch and cellulose have glucose as the basic unit
- Major component of corn syrup which is formed by hydrolysis of starch
- Corn syrup and crystalline glucose are widely used in the baking industry
FRUCTOSE:
- Found in fruits, plant juices and honey
- Sweetest of all common sugars
- Very soluble and does not crystallize easily
- In the food industry, glucose is changed to fructose by addition of the enzyme called glucose
isomerase. The product is called high fructose corn syrup which is a sweetener used in soft
drinks
GALACTOSE:
- Not normally found in its free form in foods
- Forms a bond with glucose to produce lactose (milk sugar)
- Some galactose is found in free form in fermented milk products (eg. Yogurt) where hydrolysis
of lactose has occurred
- Galactose is the basic unit of some complex carbohydrates such as vegetable gums
June 18, 2014
Disaccharides
- Consists of 2 monosaccharides linked together
- Common disaccharides in foods are sucrose (cane or beet sugar(, maltose (from corn syrup) and
lactose (milk sugar)
- Disaccharides are not absorbed into the bloodstream from the small intestine and hence are not
available as energy sources to the human body
- They must first be hydrolyzed to monosaccharides, which can then be absorbed into the
bloodstream
- Non-hydrolyzed disaccharides pass through the small intestine to the large intestine where they
are hydrolyzed by bacteria to produce acetic and lactic acids or gases
-
When produced in sufficient quantities these acids have a laxative effect or even cause diarrhea
Gas production can cause flatulence and abdominal cramps for discomfort
SUCROSE:
- Table sugar
- Extracted from sugar cane and sugar beets
- Consists of glucose and fructose chemically bonded to each other
- Present with other sugars in fruits, honey and vegetables
MALTOSE:
- Found in germinating grain and corn syrup. A product of starch hydrolysis
- Important for production of malted beverages such as beer
- Consists of 2 glucose molecules chemically bonded to each other
LACTOSE:
- Milk sugar
- Consists of glucose and galactose chemically bonded to each other
- Only found in milk and milk products
Oligosaccharides
- Carbohydrate molecules that contain 10 or fewer monosaccharides
- Includes raffinose and stachyose commonly found in dried beans
- Not digested by humans but broken down by bacteria in intestinal tract resulting in gas
formation
Polysaccharides
- Complex carbohydrates
- Up to several hundred thousand monosaccharides joined together
- Homoglucans are composed of the same type of monosaccharide
- Heteroglucans are composed of at least 2 types of monosaccharides
- May be straight chains or highly branched chains
1. STARCH (homoglucan)
o Basic storage form of carbohydrates in plants – found in abundance in seeds, roots and
tubers. Consists of only glucose molecules
o Two kinds of starch molecules: amylose and amylopectin
o Amylose has a linear chain structure
o Amylopectin has a highly branched structure
o Most natural starches consist of mictures of amylose and amylopectin
o Normal starch consists of 25% amylose and 75% amylopectin
o Starch granules swell when heated in water – a process called gelatinization
o Gelatinization is responsible for the thickening that occurs when a starch pudding or
sauce is cooked
2. DEXTRINS (homoglucans)
o Produced when starch molecules are partially broken down by enzymes, acid or dry heat
o Formed from cornstarch when corn syrup is made, when bread is toasted or when flour
is heated/browned
o
Dextrins have less thickening power than starch and are brown in colour
3. GLYCOGEN (homoglucan)
o Storage form of glucose in animals
o During digestion, carbohydrates (Eg. Starch) are hydrolyzed to glucose which is
absorbed into the blood
o Surplus glucose is converted into either fat or glycogen
o Glycogen is store in the liver and muscles temporarily until hydrolyzed to help maintain
blood glucose levels or used as fuel by muscles
PLANT FIBRES: Dietary fibre is a complex mixture of cellulose, hemicellulose, beta-glucans, pectins and
gums
FIBRE: WHY THE CONCERN?
1. Bowel health
2. Healthy weight
3. Heart health
4. Blood sugar levels
CHOOSE: 1 or 2 high fibre sources and 5 to 7 moderate fibre sources EACH DAY
Fibre in health
- Insoluble fibres (eg. Hemicellulose/cellulose) provide body with roughage
- Soluble fibres (eg. pectins and gums) are best for inhibiting cholesterol absorption
- A high fibre diet require a high water intake
- Large amount of fibre can bind minerals
- Most Canadians do not consume enough fibre
- Recommended daily intake :21-38 grams/day
- Canadians actually consume approximately 12-18 grams/day
Types of fibres
a) Cellulose (homoglucan)
o Consists of many glucose molecules linked together by beta bonds to form a linear chain
b) Hemicellulose (heteroglucan)
o Also found in plant cell walls
o Contain a variety of different monosaccharide building blocks, eg. Pentoses and hexoses
o Greatest effect is in baked goods where they improve the water binding of flour
o In bread dough they improve mixing quality, reduce mixing energy, aid incorporation of
protein and improve load volume
o Greatly retards staling of bread as compared to bread with no hemicellulose
c) Beta-glucans (homoglucan)
o Composed of glucose units that are linked together by beta bonds
o Less linear than cellulose and more soluble in water
o Oats and barley are rich sources
o In the gastrointestinal tract, it forms a viscous hydrated mass that traps bile acids and
reduces the amount of cholesterol absorbed into the body
o
o
Also decreases the rate of digestion of starch into glucose and the rate of absorption of
glucose from the gastrointestinal tract into the bloodstream
Therefore, beta-glucan may be good for diabetics as a means of controlling blood sugar
levels
d) Pectic substances (homoglucans)
o Found I both cell walls and in space between plant cells. Aid in cementing plant cells
together
o Galacturonic acid (a derivative of galactose) is the basic building block of pectic
substances
o Pectin is a pectic molecule common in fruits and is responsible for forming gels in
various jams, jellies and preserves
o Commercially, pectin is produced from apple cores or citrus peel
e) Vegetable gums/hydrocolloids (heteroglucans)
o Long chain polysaccharides
o Various hexose and pentose sugars are the basic building blocks
o Dissolved in water, they produce a thickening or texture building effect
o Gums can help to retain water, reduce evaporation rates and modify ice crystal
formation
o Widely used in the food industry: ice cream, low calorie salad dressings, low fat foods
Examples of gums/hydrocolloids
o Seaweed extracts: agar, alginate, carrageenan
o Plant seed gums: locust bean gum, guar gum
o Plant exudates: gum Arabic (used to stabilize carbonated drinks), gum
tragacanth
o Microbial gums: xanthan gum (used for cloud stabilization in orange juice),
dextran
o Modified cellulose:
1. Carboxymethylcellulose, which is used as a bulking agent in low calorie
foods and in fruit fillings
2. Methyl cellulose is used in reformed potato products and in coating and
batters to reduce oil absorption
High carbohydrate foods are often processed into more convenient forms:
CORN
- Ground to make cereals and tortillas
- Extracted cornstarch
- Cornstarch can be hydrolyzed to produce corn syrup (glucose +dextrin)
DURUM WHEAT: milled to form “semolina” (coarse flour) used to make pasta (gluten protein is what
gives pasta dough its elasticity)
WHEAT
- Wheat kernel is composed of bran (outer layer, high in vitamins, minerals and fibre), germ (the
sprouting part high in vitamins and fat) and endosperm (high in carbohydrates)
-
The bran and germ are removed during milling and the endosperm is made into flour
Wheat is also made into cereals
Note: plant carbohydrates, especially corn starch are also being used in the production of ethanol – a
more environmentally friendly fuel additive used in gasoline to reduce sulphur dioxide emissions
BREWING OF BEER
- Brewing of beer goes back over 6000 years and the methods have mostly stayed the same
Raw materials for beer manufacture include:
a) Cereal grains such as malted barley, rice, and corn which supply the carbohydrates (maltose and
glucose) for fermentation
b) Saccharomyces yeast to ferment the carbohydrates into ethyl alcohol;
c) Carbon dioxide (to purge oxygen from beer and enhance foaming);
d) Hops (to intensify flavour and colour); and
e) Water
-
-
Malted barley and other cereals are mixed with water cooked to produce a MASH. This process
gelatinizes the starches and makes them more susceptible to fermentation
The liquid portion of the mash is high in fermentable sugars and is known as WORT
The wort is transferred into a brew kettle and hops added. the mixture is brewed and the hops
residue is allowed to settle
The wort is drawn from the kettle through the bed of hops, which partially filters the wort
The wort is then cooled and inoculated with yeast for fermentation
Fermentation takes about 9 days and produces an alcohol content of approx. 4.6% as well as
some amounts of carbon dioxide
After fermentation is complete the beer is quickly chilled and passed through filters to remove
the yeast and any suspended materials
This green beer is then stored in tanks for several months, which allows further settling of finely
suspended materials and development of flavour compounds
Additional carbon dioxide is added during storage, which also helps purge the beer of any
oxygen that may be present. This is necessary because the presence of oxygen in the beer can
destroy flavour and reduce shelf life
After storage the beer is given a last fine filtration to yield a sparkling clear beverage
The beer is then bottled (known as racking) under pressure and pasteurized to prolong shelf life
June 19, 2014
Browning Reactions
1. Caramelization
o A series of chemical reactions occur when sugars are heated to temperatures greater
than their melting point
o Begins with dehydration and edns with polymerization that yields brown colours
o When the reactions are not too extensive, a desirable caramel flavour and light brown
colour results
o When the reactions are too extensive (beyond caramel formation), bitter dark coloured
compounds are formed
o Caramel is widely used in the food industry both for flavour and colour properties
o
Caramel consists of 50% digestible CHO, 25% non-digestible CHO, and 35% polycyclic
aromatic hydrocarbons
2. Maillard reaction
o Reaction between the carbonyl group (CO) of carbohydrates and amine group (NH2) of
an amino acid or protein
o A series of reactions such as fragmentation and polymerization eventually lead to the
formation of brown pigments
o In most cases this is a highly desirable reaction such as in baking and roasting
o It can be undesirable, eg. Browning and off-flavour development of skim milk powder
stored over a long period of time
CHO’s as functional foods and nutraceuticals
PREBIOTICS: dietary carbohydrates which are able to stimulate, specifically the growth of potentially
beneficial bacteria, eg. Bifidobacteria at the expense of the more harmful pathogenic microorganisms
(Group of carbohydrates that are going to stimulate the growth of very health giving organisms)
Examples of carbohydrate prebiotics
a. Oligofructose – oligosaccharide containing fructose, eg. RAFTILOSE
b. Inulin (raftiline) – polysaccharide containing fructose
c. Lactulose (disaccharide consisting of fructose chemically bonded to galactose)
d. Oligosaccharides that contain xylose, mannose, galactose and maltose
Inulin: A natural plant extract composed of linear fructose chains with mostly one terminal glucose unit
Functional Food Sources
Jerusalem Artichoke
Chicory (white carrot)
Garlic
Leek
Onion
Wheat
Insulin Content
16-20%
15-20%
9-11%
3-10%
2-6%
1-6%
Nutraceutical sources = Benefibre (containing inulin from chicory)
Metabolic summary:
o Inulin is not hydrolyzed in the mouth, stomach and small intestine
o In the large intestine, inulin undergoes complete anaerobic fermentation by bacteria
o Does not contribute any calories
o No inulin is excreted in the stool
Health benefits of Inulin
o Increases bioavailability of minerals such as calcium, magnesium and iron
o Reduces the risk of colon cancer
o Reduction in cholesterol and blood lipids
o Prevention of gastrointestinal tract infections
o Increased growth of bifidobacteria, which has the following beneficial effects:
 Produces nutrients such as B-group vitamins folic acid
 Produces digestive enzymes




Reduces food intolerance
Improves nutrient management
Reduces liver toxins, ie. Blood amines and ammonia
Competitive elimination of pathogenic microorganisms
Fats, Oils and fat substitutes
- Includes a broad group of substances that have similar properties such as insolubility in water
- Oils are liquid at room temperatures
- Fats are solid at room temperatures
There are 3 major groups of fats and oils:
A. Triacylglycerol (triglycerides)
B. Phospholipids
C. Sterols
What are the different kinds of fats (oils)?
- Saturated
- Monounsaturated
- Polyunsaturated
- Cholesterol
How fat becomes part of our food
- Added during food processing
- Added during food preparation
- Added at the table
- Found naturally in foods
Triglycerides
- Approximately 95% of the fatty substances in foods fall into this group
- Composed of three fatty acids combined with one molecule of an alcohol called glycerol
- Most fatty acids in foods don’t exist in a free form but are combined in triglycerides
- Many triglycerides have different fatty acids attached to the glycerol molecule
- The fatty acids have carbon chains as short as 4 carbons and as long as 24 (or more)
- Generally most of the fatty acids in foods have an even number of carbon atoms
- The number of hydrogen (H) atoms attached to the carbons in the chain can vary: some have all
the H atoms that the carbon can bond to – this result in no double bonds between carbon
atoms. These types of fats are called SATURATED
- Other fatty acids contain double bonds between some of the carbon atoms and do not have all
the H atoms that the carbon atom could bond – this type of fats are called UNSATURATED
Examples of fatty acids:
a. Butyric acid – found in butter has 4 carbon atoms, single bonds and is saturated
b. Stearic acid (c18) – found in seed has 18 carbon atoms, single bonds and is saturated
c. Palmitic acid (c16) – found in palm oil and cocoa butter has 16 atoms, single bonds and
is saturated
d. Oleic acid (C18:1) – found I olive oil and canola oil has 18 carbon atoms, one double
bond and is unsaturated (monounsaturated); aka omega-9
e. Polyunsaturated fatty acids contain more than 1 double bond for example:
i. Linoleic acid (C18:2) has 18 carbon atoms and 2 double bonds. It is found in
most foods especially oilseeds such as canola and soybean; aka omega-6
ii. Linolenic acid (C18:3) also has 18 carbon atoms but contains 3 double bonds
and is found mostly in soybean and hempseed; aka omega-3
Linoleic and linolenic acids are essential fatty acids
The cis-trans configuration
In the cis configuration the H atoms are on the same side of the double bond
In the trans configuration the H atoms are on the opposite sides of the double bond
Trans fatty acids have a higher melting point than the cis fatty acids
-
Trans fatty acids are formed mostly during the process of hydrogenation
Hydrogenation of oils is carried out to:
o Make the oil more solid at room temperature (eg. Margarine and shortening)
o Increase the stability (ie. Smoke point) of these oils to thermal temperatures (frying oils)
o Prevent or slow rancidity
o The amount of hydrogenation will affect the amount of trans fatty acids produced:
 Shortening (medium level hydrogenation)
 Contains 10-20% trans fatty acids
 Soft tub margarine (medium level hydrogenation)
 Contains 13-20% trans fatty acids
 Hard margarine (high level hydrogenation)
 Contains 25-28% trans fatty acids
o Many specialty soft tub margarines (eg. Becel, fleischmann’s) that are currently solf are
not hydrogenated, but consist of careful blend of different oils and fats
o Therefore consumption of non-hydrogenated margarine is recommended over
hydrogenated type for maintaining a heart healthy status
Phospholipids
Present in foods in relatively small amounts but play important roles as emulsifying agents, ie.
Substances that facilitate emulsion formation
- Lecithin is a phospholipid used in various foods including margarine
-
Egg yolk and soybean oil are good sources of phospholipids
Sterols
- Cholesterol is probably the best known sterol found in animal foods
- Vitamin D is also a sterol
- Plants do not manufacture cholesterol but they do manufacture other sterols called
phytosterols
- Phytosterols are not well absorbed from the gastrointestinal tract and may actually interfere
with absorption of cholesterol
- Therefore, some types of foods such as margarine (eg. Benecol) are fortified with phytosterols
to help reduce the amount of cholesterol absorbed into the blood stream
Winterization of oils
- A process to produce salad oils that do not crystallize (ie. Become cloudy) at refrigerator
temperatures
- Oils can become cloudy at lower temperatures because some of the triglyceride molecules
crystallize or become solid
- Involves lowering the temperature of oil to a point at which the triglycerides with high melting
points crystallize
- The oil is filtered to remove the crystals and the remaining oil has a lower melting point and
does not crystallize at refrigerator temperatures
Deterioration of fat
- The chemical spoilage that commonly occurs with fats and fatty foods is called rancidity
- Highly unsaturated fats/oils such as polyunsaturated fats are much more susceptible than
saturated or monounsaturated fats
- Foods that easily go rancid are nuts, wheat germ and whole wheat flour
There are two types of rancidity:
1. Oxidative rancidity
o Occurs primarily with the unsaturated fatty acid portions of triglycerides
o Reaction begins with the addition of oxygen to carbon atoms next to a double bond in a
fatty acid. The reaction results in formation of hydroperoxide
o Hydroperoxide molecules readily breakdown into volatile products that have off odours
and flavours characteristic of rancid fat
o Oxidative damage can be prevented or slowed down through the use antioxidants such
as BHT or vitamin E (or BHA)
2. Hydrolytic rancidity
o Hydrolysis involves breaking of chemical bonds and in the process the addition of water
o Hydrolytic rancidity is the result of the breaking of triglyceride structure composed of
short chain fatty acids
o Results in the production of glycerol and free short chain fatty acids such as butyric acid
ad caproic acid (found in butter)
o The short chain fatty acids are volatile and produce off flavours and odours
June 20, 2014
Final exam
Friday 9am – 11am
120 marks
50 MC
20 T/F
20 terms
30 marks long answer
Fat Replacers
- Products or ingredients that can replace part or all of the fat in foods
- It is difficult to find a fat substitute that will perform well in all food products
Carbohydrate-based replacers
- Includes derivatives of cellulose, maltodextrins, gums, modified starches and polydextrose
- They produce a mouth feel that is similar to that associated with fat but they do not taste like
fat and do not function like fat in cooking
Protein-based replacements
- “simplesse” is a microparticulated protein, which is produced by reshaping milk and egg white
protein into tiny round particles
- The process produces protein particles so small that they are perceived as fluid by the mouth
- Used to manufacture low-fat frozen and refrigerated products such as ice cream and other dairy
products, but cannot be used for frying
Fat-based replacements
- Long chain fatty acids can be combined with sucrose to produce a compound known as sucrose
polyester
- This product is neither digested nor absorbed from the gastrointestinal tract (ie. Has no caloric
value), but has characteristics similar to triglycerides in food preparation
- One of such compound approved for use in USA is known as OLESTRA and foes by the brand
name of OLEAN
- Olestra is not approved for use in Canada
- Olestra has a core molecule of sucrose to which 8 fatty acids are chemically bonded. The
digestive enzymes do not recognize this structure and olestra passes through the digestive
system undigested
- It is the most successful of the fat substitutes because it can be used in cooking or frying and it
tastes like fat
Safety Concerns
A. The presence of olestra in the large intestine causes diarrhea, gas and cramping in some people
(anal leakage)
B. Olestra can prevent absorption of fat soluble vitamins
C. May cause the loss of essential phytochemicals such as carotenes from the body
Fats/Oils as functional foods and nutraceuticals
1. Conjugated linoleic acid (CLA)
o In linoleic acid, the two double bonds are separated by two single bonds
 -CH = CH-CH2-CH = CHo In conjugated linoleic acid, the two double bonds are separated by one single bond
 -CH = CH-CH = CHo CLA is an essential fatty acid found mostly In animal products such as milk and meat
o Meat of ruminants – cows, sheep and other animals that chew their cud contains CLA,
while non-ruminant meats such as turkey, chicken and pork do NOT contain CLA
o This is because bacteria in the stomach of ruminants convert linoleic acid to CLA, which
is absorbed into the animal tissue
o Non-ruminants do not have this type of bacteria, so they cannot produce CLA
o CLA is available in pills sold as over the counter products in grocery and drug stores
o Has been found to suppress atherosclerosis (plaque formation that leads to heart
attack) in blood vessels
o Potential anti-carcinogenic effect has been show in rats
o A year 2000 survey determined that women with the most CLA in their diets had 60%
reduction in the risk of breast cancer
o Has been shown to reduce fat mass and preserve muscle tissue in rats. Human benefit
for weight loss has not been completely demonstrated
o Lowes insulin resistance which may help prevent adult-onset of diabetes
o Enhances immunity and resistance to infections
Important: please consult your doctor before you take CLA
2. Omega-3 and omega-6 fatty acids
o Linoleic acid (C18:2) is called omega 6
o Linolenic acid (C18:3) is called omega 3
o Both fatty acids have been reported to protect against cardiovascular and inflammatory
diseases
o It is the ratio of omega 3 (n-3) to omega 6 (n-6) that is important. The higher the ratio
the better the benefits
o The low incidence of cardiovascular disease in Inuit population has been attributed to
the high n-3:n-6 ratio in their diet which is based principally on fish products
o Fish oil contains a high n-3:n-6 ratio and has been shown to decrease serum triglyceride
and cholesterol levels
o Fish oil also lowered blood pressure in hypertensive patients
Proteins
- A protein is a chain of amino acids joined together by a peptide bond
- Proteins contain carbon, hydrogen, oxygen, nitrogen an sulfur
- Specialized protein molecules called ENZYMES catalyze a number of important reactions in
foods
Protein structure
- Amino acids are joined by peptide bonds to produce long chains that constitute the primary
structure of proteins
- Coiling of the long chain is the secondary structure
- Folding of the coil is the tertiary structure
-
20 different amino acids are used as building blocks to form proteins
9 amino acids are considered essential in human nutrition
Balance of amino acids in a protein determine its biological value and nutritional quality
Proteins with high biological value, ie. Complete proteins contain adequate amounts of essential
amino acids
Foods with high biological value proteins include milk, eggs, cheese, meat, fish and poultry
Different plant proteins can be combined to provide diets with high biological value. Eg. A
mixture of legume (beans or peas) and cereal (wheat, rice or corn)
This is important in vegetarian lifestyle
Essential and nonessential amino acids:
Essential
Nonessential
Lysine
Alanine
Tryptophan
Arginine
Phenylalanine
Aspartic Acid
Methionine
Cysteine
Leucine
Glutamic acid
Isoleucine
Glycine
Threonine
Proline
Valine
Serine
Histidine*
Tyrosine
Asparagine
Glutamine
*histidine is essential only in infants
There are 2 characteristics of high quality proteins (eg. Egg white):
1. Contain the essential amino acids proportional to the body’s need for them
2. Are digestible so that sufficient numbers of the amino acids reach the body’s cells
Properties of proteins
1. Buffering
o The amine group acts as a base (alkaline) whereas the carboxyl group acts as an acid
o Because of this property proteins can resist changes in pH and are called buffers
o Important in food preparation since the degree of acidity or alkalinity can affect the
quality of a food
2. Denaturation and Coagulation
o Denaturation involves unfolding of protein structure without breakage of peptide bonds
o Denaturation is caused by cooking, freezing, changes in pH, salts and mechanical action
o In most cases denatured proteins are less soluble and if it is an enzyme, it will lose its
functional ability
o Continuous denaturation (unfolding) can lead to recombination of the protein molecules
in different ways to produce a new molecular shape
o The newly shaped molecules may bond together to form a continuous network referred
to as coagulation. Eg. Coagulation of egg white when heated
3. Enzymes
o Act as catalysts that speed up chemical reactions without being used up in the reaction
itself
o Enzymes do not stop functioning when an animal is slaughtered or when a plant is
harvested, therefore, we must consider enzyme activity when dealing with foods
o Names of enzymes often include the substrate of substance on which they act, and have
an “ase” ending. Eg. Lactase (acts on lactose), protease (acts on proteins), lipase (acts on
lipids)
o The name of an enzymes may also describe the reaction that is catalyzed. Eg. Oxidase
(catalyzes oxidation reactions)
o Enzymes are used in foods such as meat tenderizers (bromelain, papain), clotting of milk
(renning or chrymosin)
o Enzymatic browning is an undesirable browning reaction that occurs when some fruits
and vegetables such as banana, apple, potato are cut and exposed to oxygen
o The most commong enzyme responsible for browning is called polyphenol oxidase
o The browning reaction can be blocked by denaturing the enzyme by using heat, by
excluding oxygen by covering the surface of the food or by adding ascorbic acid (vitamin
C)
June 23, 2014
Functions of proteins in FOODS
1. Absorb and bind water
Food system – sausages, cakes and breads
2. Thicken and increase viscosity
Food system – soups and dairy products
3. Emulsify fats
Food system – bologna, ice cream, soups, cheese and doughnuts
4. Binding flavour
Food system – simulated meats
5. Production of foams
Food system – sponge cakes and whipped toppings
6. Dough formation
Food system – wheat (gluten) proteins are responsible for the unique baking properties of
wheat flour
Uses of Proteins
1. Bacterial enzymes can be used as dough conditioners in place of chemicals such as potassium
bromate
2. Soybean and pea proteins can be textured into fibers to fabricate meat analogs. This is known as
‘texturized vegetable protein (TVP)’
3. Soluble proteins are used in infant formulas, meal replacement drinks and sport drinks
4. Gelatin (collagen protein) is used in candies, jello powder and pharmaceutical capsules
Gelatin is a protein obtained from the extract of cattle hooves and bones
Have excellent gelling properties but low biological value
5. As a sweetener – aspartame (nutrasweet) is composed of 2 amino acids (aspartic acid and
phenylalanine with a methyl group) bonded together
o Aspartame is 180-200 times sweeter than sucrose (table sugar) and is used in diet drinks
o Because of the intense sweetness, aspartame is used at very low levels that provide few
calories
Animal Proteins
1. Meat
o Broadly defined, meat includes muscle tissue and organs of beef, veal, lamb, pork,
poultry and fish
o Red meat has negligible carbohydrate content as the glycogen is used up in the
continuing metabolic processes after slaughter
o Major components of red meat are water, protein and fat
o High water content and neutral pH makes meat susceptible to spoilage – this can be
reduced by curing (salt addition) or drying
o Meat usually has some visible fat called marbling. Presence of fat increases juiciness and
gives better eating quality
Due to consumer health concerns, some animals are bred to have leaner meat (less
marbling)
There are 3 different types of proteins in muscle tissue: a. actinomyosin, b. collagen and
c. elastin
o
o
o
o
o
o
o
The toughness of meat is directly related to the amount of collagen it contains
That is why older animals which have accumulated high levels of collagen yield tougher
meat than young animals
The colour of meat is often used to judge freshness and it is usually wrapped in material
that is permeable to oxygen to preserve the red colour
Without oxygen, beef is normally blueish-puple. When meat is not fresh it turns brown
Fish flesh is highly perishable because of the high levels of unsaturated fatty acids which
can be readily oxidized
Fish flesh is rich in a chemical calls trimethylamine oxide (TMAO)
After capture the TMAO is converted to trimethylamine (TMA) that is responsible for
the ‘fishy’ odour
2. Milk and dairy products
o Milk is the near perfect food – it is an important source of high quality protein, minerals,
B vitamins and energy
o Milk is composed of two protein fractions:
 Casein (80%) and whey (20%)
o During the manufacture of cheese, acid or rennin (an enzyme) is added to coagulate
most of the casein proteins while the whey proteins remain in solution
o
o
o
Whey proteins are composed mostly of beta-lactoglobulin, alpha-lactalbumin
During processing, fluid milk and yogurt are pasteurized
In another product called ultra-high temperature (UHT) milk, the milk is treated to
remove all viable microorganisms, ie. The product is sterile
3. Eggs
o
o
o
Eggs have 2 major parts – the egg white and the egg yolk
Major protein of the egg white is ovalbumin
Major proteins of the yolk are the lipoproteins – high density lipoproteins and low
density lipoproteins
Functional characteristics of eggs
1. Emulsification: lipoproteins and phospholipids present in the egg yolk help to keep fat dispersed
in water
2. Foaming: proteins in the egg white have a high capacity to form strong protein films that
surrounds air bubbles to produce stable foams
3. Coagulation: egg white proteins can set and form a gel during heating
Plant Proteins
- Plant proteins can be divided into four broad groups based on solubility properties
a. Albumins – soluble in water
b. Globulins – soluble in salt solutions, but insoluble in water
c. Gliadins – soluble in 70-90% alcohol
d. Glutelins – insoluble in neutral aqueous solutions, saline solutions or alcohol. Can only
be dissolved in dilute alkaline solution
Plant protein crops
1. Cereals
o Have protein contents not greater than 15-17% (eg. Wheat, corn, rye, rice, oats, barley)
o In wheat, the principal proteins are the gliadin and glutelin fractions, which represent
about 80% of the endosperm protein
o Gluten is a complex formed from gliadins and glutelins following hydration and mixing of
wheat flour
o The hydrated gluten complex forms a 3 dimensional viscoelastic network that gives
wheat flour its valued dough and bread making characteristics
2. Pulse and oilseed (legume) storage proteins
o Contain higher protein contents, ranging from 18-45% (eg. Peas, soybean, canola,
mustard)
o Contain very little amounts of gliadin and glutelin. Majority of the proteins are soluble in
water or salt solutions
Single-cell proteins
- Involves production of proteins from microorganisms such as yeasts, bacteria and fungi
- Commercial production of edible single cell proteins uses the fungi called Fusarium venenatum
- The protein from fungi is called mycoprotein
- Mycoprotein from F. venenatum has been approved for human consumption in parts of Europe
and as well as in the USA
- On the basis of dry cell weight, the mycoprotein supplies 50% protein, 13% lipids and 25% fibre
- The mycoprotein contains no cholesterol
- It is sold under the trade name “Quorn”
Food uses of mycoproteins (Quorn):
1. As a muscle fibre replacer in the manufacture of simulated meats like vegetarian burger
2. As a fat replacer in foods
3. As a cereal replacer in the manufacture of breakfast cereals
Proteins as functional foods and nutraceuticals
1. Soybean protein
o Lowers cholesterol content in the body
o May also be used in the management and prevention of cancer
o Reduces bone loss
o Reduces menopausal symptoms
o Enhances immune system
o In sports nutrition to improve recovery
o Protease inhibitors from soybean have potential anti-viral activity. Some current antiHIV cocktails contain soybean protease inhibitors
2. Biologically active (bioactive) peptides and amino acids
o Enzymatic hydrolysis of proteins yields peptides, which are smaller forms of proteins
o Bioactive peptides and amino acids provide physiological benefits such as disease
prevention or treatment
a. Antihypertensive peptides
 Inhibit the activity of angiotensin converting enzyme (ACE), the principal
causative agent of hypertension. The peptides are called ACE inhibitors
 ACE catalyzes the conversion of angiotensin 1 (Ang1) to angiotensin 2 (Ang 2)
 Ang 2 causes constriction of blood vessels resulting in development of high
blood pressure
 Peptide inhibitors bind to ACE and prevent formation of ang 2, thereby
preventing rise in blood pressure
 A commercial product called “BIOZATE” contains peptide ACE inhibitors from
dairy whey protein hydrolysate
b. Opioid peptides
 Have morphine like properties and increase analgesic behaviour
 Modulate social behaviour
 Prolong gastrointestinal transient time by inhibiting intestinal peristalsis and
motility
 Stimulate endocrine responses such as secretion of insulin and somatostatin
 Stimulate uptake of high fat diet
c. Caseinophosphopeptides
 Obtained from enzymatic hydrolysis of casein (milk protein). Present in a
complex with calcium phosphate
 This complex formation provides enhanced absorption of calcium in the small
intestine
 The peptides also inhibit caries lesions through re-calcification of the dental
enamel. Hence, their application in treatment of dental disease has been
proposed
d. Immnomodulatory peptides
 Increase phagocytotic activity of human macrophages. Macrophages are cells
that destroy foreign bodies that enter our body
 Increase proliferation of white blood cells
 Some peptides present in yogurt may suppress development of colon cancer
e. Branched-chain amino acids (BCAA)
 BCAA are valine, leucine and isoleucine. They are preferentially incorporated
into proteins by the muscles
 Therefore, they are used to reduce the muscle wastage that occurs in people
with liver diseases
 They are also used as body building agents especially in athletes that need
increased muscle mass
f.
Arginine-enriched foods
 Arginine is the precursor of nitric oxide (NO) in the body. Discovery of NO was
the basis of a Nobel prize in medicine
 NO enhances communications between cells and is very important in
neurotransmissions, ie, the ability of nerve cells to function properly
 NO is also involved in maintaining normal blood flow in blood vessels by
increasing the ability of the vessels to dilate
 Therefore, increased arginine consumption may be used to reduce high blood
pressure
 Arginine is also a major component of some natural health products that are
sold to treat erectile dysfunction in men