General References

G. V. Barbosa-Cánovas and H. Vega-Mercado, Dehydration of Foods, Chapman and Hall, New York, 1996.

D. A. Corlett, HACCP User's Manual, Aspen Publishers, Gaithers-burg, Md., 1998.

J. F. Diehl, Safety of Irradiated Foods, 2nd ed., Marcel Dekker, New York, 1995.

W. A. Gould, CGMP's /Food Plant Sanitation, CTI Publications, Baltimore, Md., 1994.

W. A. Gould, Unit Operations for the Food Industries, CTI Publications, Baltimore, Md., 1996.

D. R. Heldman and D. B. Lund, Handbook of Food Engineering, Marcel Dekker, New York, 1992.

S.D. Holdsworth, Aseptic Processing and Packaging of Food Products, Elsevier, New York, 1992.

P. Jelen, Introduction to Food Processing, Prentice-Hall, Engle-wood Cliffs, N.J., 1989.

N. G. Marriott, Essentials of Food Sanitation, Chapman and Hall, New York, 1997.

N. N. Potter and J. H. Hotchkiss, Food Science, 5th ed., Chapman and Hall, New York, 1995.

G. L. Robertson, Food Packaging: Principles and Practice, Marcel Dekker, New York, 1993.

R. P. Singh and D. R. Heldman, Introduction to Food Engineering, 2nd ed., Academic Press, New York, 1993.

K. J. Valentas, E. Rotstein, and R. P. Singh, Handbook of Food Engineering Practice, CRC Press, New York, 1997.

R. C. Wiley, Minimally Processed Refrigerated Fruits and Vegetables, Chapman and Hall, New York, 1994.

James Faller University of Illinois Urbana, Illinois

FOOD PROCESSING: EFFECT ON NUTRITIONAL QUALITY

The definition of processing is "a natural phenomenon marked by gradual changes that lead toward a particular result"; "a series of actions or operations conducing to an end"; or "a continuous operation or treatment especially in manufacture" (1). Food processing, therefore, refers to the series of actions involved in order to prepare and preserve a food supply by some continuous operation or treatment to achieve as a goal a safe, high-quality product with extended shelf life.

Changes that occur to food quality may be thought of as two types: deterioration and spoilage. Deterioration involves changes in quality induced by physicochemical and/ or biochemical reactions taking place with or without the intervention of a physical environment (such as oxygen, carbon dioxide, water, light, heat, etc). Spoilage, on the other hand, generally refers to changes in quality due to action of biological agents such as bacteria, molds, or insects. Effects of deteriorative reactions and spoilage agents on food quality result in changes in both sensory properties (ie, appearance, flavor, texture) and nutritive value (vitamin content, protein value, etc). The extent to which these reactions can occur depends on the sensitivities and types of food products considered. For example, certain fruits such as strawberries or raspberries may be readily spoiled by the presence of molds. Green peas or beans, on the other hand, lose flavor and result in undesirable textures due to enzyme-induced reactions.

Through various types of food processing, quality factors can be maintained or extended, the extent of which depends on the food product to be considered. By canning fruits and vegetables (eg, pears, peaches, peas, beets) with proper heat sterilization and packaging, these products will not suffer spoilage, although they may deteriorate to some extent in terms of color, flavor, and texture. The extent of these changes depends on a wide array of factors, including storage conditions after packaging. Factors affecting quality of food products include: (1) initial quality of the raw materials and handling from harvesting to the manufacturing plant; (2) pretreatment (including cleaning, sanitizing, washing, aspiration, screening, filtration, chlorination, fumigation, etc); (3) sorting (removal of extraneous materials); (4) peeling, coring, dehairing, de-feathering, husking, stemming, and so on; (5) disintegration/physical separation in cases where grinding, pulping, pressing, or expelling are needed, generally followed by screening, filtering, or centrifugation; and finally, of course (6) the final finished food manufacturing step. These final manufacturing steps comprise a myriad of different types of food processes including clarification/filtration; crystallization; curing/smoking; dehydration; evapo-

only 3 cm by conduction versus about 8 cm in the conventional #10 can. Shorter heat treatments allow the preservation of a greater variety of specialty products. The half-steam-table size eliminates cleaning of pans, because the opened unit serves as a serving tray. Other semirigid systems have been developed to replace the steel can for single-portion service. These containers generally use a heat-sealed or glued paper-foil-plastic laminated closure.

Aerosol containers have played a specialized role in the food industry as dispensers for such foods as whipped toppings (using nitrous oxide as a propellant), cake frosting, and barbecue sauces. Special filling techniques and product formulations are required because the aerosol package cannot be heat sterilized once it has been sealed.

Packaging forms an integral part of most food processing. For this reason, studies of storage conditions over a range of temperatures, relative humidities, and handling conditions must be made to determine the suitability of a package. Packaging in contact with foods must be tested for migration of packaging components under actual conditions of use, and pickup of off-flavor must be evaluated on a product-by-product basis. Because of potential migration of packaging materials into foods, current food and drug regulations should be consulted prior to marketing foods packaged in nonstandard materials.

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