effects of food processing on the nutrients in foods
TRANSCRIPT
• 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 FoodsLose 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 FoodsLose 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 AntioxidantsProtect 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
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