Effects of Food Processing
on the Nutrients in Foods
• Many consumers rely on packaged
and processed foods for convenience
and speed
– Lose control over what foods contain
– Food processing involves trade-offs
• Makes food safer, or gives food a longer
useable lifetime, or cuts preparation time
• At cost of some vitamin and mineral losses
• Most forms of processing aim to
extend the usable life of a food
– To preserve a food, a process must
prevent three kinds of events
• Microbial growth
• Oxidative changes
• Enzymatic destruction
Canning
– A method of preserving food by killing
all microorganisms present in the food
and then sealing out air
– The food, container, and lid are heated
until sterile
• As the food cools, the lid makes an airtight
seal, preventing contamination
Do Canned Foods
Lose Nutrients?
• Fat-soluble vitamins and most minerals
are relatively stable
– Not affected much by canning
• Three vulnerable water-soluble vitamins
– Thiamin
– Riboflavin
– Vitamin C
Do Canned Foods
Lose Nutrients?
• Some minerals are added when
foods are canned
– Important in this respect is sodium
chloride, salt, which is added for
flavoring
Freezing
• A method of preserving food by
lowering the food’s temperature to a
point that halts life processes
– Microorganisms do not die but remain
dormant until the food is thawed
– Dramatically slows enzymatic reactions
Freezing
• Frozen foods may have a nutrient
advantage over fresh
– Fresh foods are often harvested unripe
– Frozen foods are first allowed to ripen
in the field
• Allows the food to develop nutrients to their
fullest potential
Drying
• A method of preserving food by
removing sufficient water from the
food to inhibit microbial growth
• Eliminates microbial spoilage
• Microbes need water to grow
• Reduces the weight and volume of
foods
• Foods are mostly water
Drying
• Commercial drying does not cause
major nutrient losses
– Foods dried in heated oven at home
may sustain dramatic nutrient losses
– Vacuum puff drying and freeze drying
• Take place at cold temperatures
• Conserve nutrients especially well
Extrusion
• A process by which the form of a
food is changed
• Such as changing corn to corn chips
• Not a preservation measure
• In this process, the food is heated,
ground, and pushed through various
kinds of screens to yield different
shapes
• Results in considerable nutrient
losses
– Nutrients are usually added to
compensate
• Foods this far removed from the original
state are still lacking significant nutrients
(notably vitamin E) and fiber
Food Additives
• Substances that are added to foods
but are normally not consumed by
themselves as foods
Food Additives
• Compared with unregulated and
untested “dietary supplements” sold
directly to consumers, the 3,000
food additives in the U.S. are strictly
controlled and pose little cause for
concern
• Manufacturers use food additives to
give foods desirable characteristics
– Color
– Flavor
– Texture
– Stability
– Enhanced
nutrient
composition
– Resistance to
spoilage
Regulations Governing
Additives
• The FDA has the responsibility for
deciding what additives shall be in foods
– To obtain permission to use a new additive
in food products, a manufacturer must test
the additive and satisfy the FDA that
• It is effective
• It can be detected and measured in the final
food product
• It Is safe for consumption
The GRAS List
• Many substances were exempted
from complying with the FDA
procedure when it was first instituted
because they had been used for a
long time and their use entailed no
known hazards
– Some 700 substances were all put on
the generally recognized as safe
(GRAS) list
Additives must not be used
– In quantities larger than those
necessary to achieve the needed
effects
– To disguise faulty or inferior products
– To deceive the consumer
– Where they significantly destroy
nutrients
– Where their effects can be achieved by
economical, sound manufacturing
processes
Antimicrobial Agents
• Preservatives that protect food from
the growth of microbes that can spoil
the food and cause foodborne
illnesses
Antimicrobial Agents
• Salt and Sugar
– The best-known and most widely used
antimicrobial substances
– Salt is used to preserve meat and fish
– Sugar preserves jams, jellies, ad
canned and frozen fruits
– Both work by withdrawing water from
the food
• Microbes cannot grow without water
Antimicrobial Agents
• Nitrites
– Added to meats and meat products to
• Preserve their color
• Enhance their flavor
• Protect against bacterial growth
How Do Antioxidants
Protect Food?
• Food can go bad when it undergoes
changes in color and flavor caused
by exposure to oxygen in the air
(oxidation)
– Often these changes involve little
hazard to health
• But they damage the food’s appearance,
taste, and nutritional quality
– Antioxidant preservatives protect food
from this kind of spoilage
• Examples of common antioxidant
additives
– Vitamin C
– Vitamin E
(tocopherol)
– Sulfites
– BHA and
BHT
• Sulfites
– Prevent oxidation in many processed
foods, alcoholic beverages, and drugs
– Were used to keep raw fruits and
vegetables in salad bars looking fresh
• Practice was banned after a few people
experienced dangerous allergic reactions
to the sulfites
• FDA now prohibits sulfite use on food
meant to be eaten raw
– With the exception of grapes
• BHA and BHT
– Prevent rancidity in baked goods and
snack foods
Artificial Colors
• Only about 10 of an original 80
synthetic color additives are still on
the GRAS list
– Among the most intensively
investigated of all additives, artificial
colors are much better known than the
natural pigments of plants
• Food colorants only make foods
pretty
– Other additives, such as preservatives,
make foods safe
– With food colors we can afford to
require that their use entail no risk
• With other food additives, we must weigh
the risks of using them against the risks of
not using them
• Close to 2,000 artificial flavors and
enhancers are approved
– Safety evaluation of flavoring agents is
problematic because so many are
already in use
– The flavors are strong and are used in
tiny amounts unlikely to impose risks
• And they occur naturally in a wide variety
of foods
Incidental Food Additives
• Are really contaminants from some
phase of production, processing,
packaging, or consumer preparation
– Include tiny bits of plastic, glass, paper,
tin and the like from packages and
chemicals from processing, such as
solvents used to decaffeinate some
coffees
Nutrient Additives
• Include
– Enrichment nutrients added to refined
grains
– Iodine added to salt
– Vitamins A and D added to dairy
products
– Nutrients used to fortify breakfast
cereals
REMEMBER…
The more heavily processed foods are
the less nutritious they become