Food Processing

Individuals, companies, and corporations in the business of food processing have three basic responsibilities: (1) to ensure food safety, (2) to enhance food stability, and (3) to alter the form of feedstocks and ingredients to fit consumer demands. Food safety is paramount. The hazards associated with processed foods can be microbial, physical, or chemical. Microbial hazards are from pathogenic microorganisms or viruses that either invade the consumer or produce toxins in food during growth and dormancy phases. Examples of physical hazards are broken glass, rocks, or metal pieces, which can inflict serious harm if consumed inadvertently. Chemical hazards can come from cleaning compounds or other equipment maintenance fluids or can be associated with overuse of regulated food ingredients (such as sulfites in wine that control oxidative discoloration and growth of undesirable microorganisms but that can lead to bronchospasms in some individuals). Many of the processes used in food production are specifically used to ensure food safety.

Simply ensuring food safety does not, however, guarantee stability for the product shelf life desired by consumers. For example, retorting canned low-acid food through 12 decimal reductions for Clostridium botulinum to prevent botulism will only result in approximately a two-decimal reduction in Bacillus stearothermophilus, a thermophilic organism that causes flat sour spoilage if canned foods are stored above 38°C. Therefore, canned low-acid foods generally receive a more severe heat treatment than is required for ensuring food safety. In another example, refrigeration can prevent the growth of most pathogenic microorganisms but will not prevent enzyme activity or the growth of spoilage psychrophiles (some pathogens, such as Listeria monocytogenes or Yersinia entercolitica, are now being found to be psychrophilic). Food spoilage can result from nonpathogenic microorganisms, enzyme activity, chemical deterioration (eg, oxidation of lipids), contamination from pests, and mechanical damage.

In addition to safety and stability, much of modern food processing is designed to provide food to the consumer in a form convenient for use and desirable for taste. For example, while potatoes can be stored safely for long periods, precooking, mashing, and drum drying renders them in a form that can be consumed simply by adding hot water. Addition of dried spices or cheese flavoring may further enhance the appeal of the product. Ice cream can safely be packaged in one-gallon tubs and stored for months, but an individual serving on a stick with a chocolate coating will be much more convenient and appealing.

Conventional food processing, regardless of type of food, can be divided into three classes: separation, assembly, and preservation. These can occur at harvest, at the food-processing plant, or even at the point of retail sales. Increasing emphasis is being placed on field processing as exemplified by the widespread use of mechanical harvesters fitted with cleaning, sorting, color measurement, and size-grading systems. The known food-processing operations are grouped in Tables 1, 2, and 3.

Foods can be categorized as living tissue, or raw foods, and nonliving tissue. Living tissue foods include fresh fruits, vegetables, meats, and grains. Processes for preserving living tissue are considered separately from those used for the preservation of nonliving tissue, for example, canned, frozen, and dried foods.

FOOD COMPOSITION Chemical Composition

Virtually all foods are derived from living tissues, although individual nutrients and additives, including lipids, carbohydrates, amino acids, and vitamins, can be synthesized. A nutritionally adequate dietary regimen of pure nutrients would be neither economically nor aesthetically useful except for medical applications such as intravenous feeding. Foods consist of hundreds of compounds because they are derived from the life processes of living tissues. The components of food composition are the nutrients that are essential to sustain life processes. Information on specific compounds in foods can be obtained from the literature, as can tables listing the nutrient composition of commodities, refined food components (eg, sucrose and gelatin), and processed as well as standardized formulated foods (eg, bread and margarine). Tables of nutrient composition are available for most foods found worldwide and contain quantitative data on moisture and caloric value (kJ or kcal x 4.184) and on lipid, protein, carbohydrate, fiber, ash, mineral, and vitamin contents. Tables of food composition are useful only as a first approximation to the actual nutritive value and gross chemical composition of

Table 1. Separation Unit Operations of the Food Industry Arranged by Mode of Separation and Phases Being Separated

Phases to be separated

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