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 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

• 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