A vast majority, if not all, of the food you have consumed in your life has been processed. Everything that is sold at a grocery store has been canned, waxed, frozen, dried, bottled, wrapped, baked, packaged, or in some way altered. Food processing is the set of methods used to transform fresh food items into retail food products and how they are stored, packaged, and delivered. It encompasses the vast range of procedures involved in turning grapes to bottles of wine, wheat kernels to pre-sliced loaves of bread, and live animals to the cuts of meat available for purchase.
The primary purpose of most food processing is to prevent spoilage. Fresh produce that would spoil in days if unpreserved can be made to last weeks if refrigerated, months if dried or frozen, and years if canned. Food processing also reduces the risk of food-borne diseases since fresh materials are more likely to carry harmful pathogens.
The most common methods of food processing involve preservation through chemical alterations such as dehydration, temperature adjustment, and the use of additives.
Freezing, canning, pasteurizing, and drying all function by destroying or impeding the microorganisms that cause spoilage and food-borne illness. Freezing or drying food prevents the survival of bacteria through depriving them of heat or water; and cooking or pasteurization destroys them through heat.
Freezing allows for the preservation of perishable food products with minimal to no loss of flavor, color, and nutritional value. However, some food items are unsuitable for freezing due to an undesired change in texture – tomatoes, for instance, become extremely soft when unfrozen.
Many liquid products such as milk, eggs, and juice are pasteurized – a process involving brief, mild heating to destroy bacteria and deactivate enzymes so that the product can retain its flavor and color.
Canned food products, present in 98% of American households, can remain unspoiled for decades through pasteurization and sealing to prevent further contamination.
Fruits and vegetables frequently undergo sulfiting – exposure to sulfur dioxide gas or similar chemicals to preserve color and flavor. Most vegetables are also blanched (precooked in water or steam).
Concentration involves evaporation of water in liquid products. The liquids are sealed in a vacuum so that they can boil at low temperatures to minimize heating of the product. Soups, milk, fruit juice, and other liquids are frequently concentrated before they are canned or frozen to reduce packaging, shipment, and storage costs.
Food processing also utilizes chemical additives such as food coloring, artificial flavors, sweeteners, flavor enhancers such as monosodium glutamate (MSG), thickening agents such as xanthan gum, and chemical preservatives such as sodium nitrite and sodium benzoate. Propionates are added to bread to prevent mold, antioxidants are added to meat to prevent rancidity, and emulsifiers are added to French dressing to prevent separation.
Processing allows for more efficient distribution of food through a significant reduction in storage and transportation costs. Drying and freezing fruits and vegetables reduces their weight by half, cut sweet corn is a third the weight of corn on the husk, and a can of frozen orange juice concentrate represents the equivalent of four cans of juice.
The shipment and distribution of raw material in fresh form results in considerable waste and spoilage. Processing allows for the total utilization of the crop or animal. Apples that are rejected from fresh-market packinghouses can be made into juice, the peel can be processed for pectin, and the remainder can be made into cattle feed. The extreme variance of the modern human diet is only possible through advanced methods of food processing and preservation.