FOOD PRESERVATION

any of a number of methods by which food is kept from spoilage after harvest or slaughter. The practice of preserving food can be traced to prehistory, when fruits and vegetables were dried, cereal grains were parched, and fish and game were salted and dried. These age-old methods developed very slowly and were purely empiricalfermentation, drying, smoking, and curing with salt being the principal techniques. As the biological causes of food spoilage became better understood, rapid advances followed, and appropriate methods were soon developed for dealing with the causative agents. Since most foods either carry or eventually acquire bacteria, molds, or yeasts, microorganisms are the major cause of food spoilage. Other factors leading to deterioration or spoilage are the natural enzymes present in some foods and various chemical reactions, particularly oxidation. Some factors that lead to spoilage in one food are regarded as desirable in another instance and may be, indeed, essential for the protection of certain foods. For example, yeasts are applied in making wine, bacteria in the manufacture of sour milk and pickled products, and molds in cheese making. Enzymes are used in both cheese production and in brewing, and the browning of roasts and bread crust is a type of chemical reaction that in many other foods leads to deterioration and spoilage. Among the major processes for food preservation are cooling or freezing, dehydration, canning, smoking, salting, candying, and the addition of chemical preservatives and inhibitors. Often several principles are applied in combination. For instance, cabbage is preserved as sauerkraut in the presence of salt and by the chemicals produced by the microorganisms during fermentation, and much of this product is later marketed in cans after heat sterilization. Some frozen food products are heated before freezing in order to deactivate the enzymes or to reduce the number of viable organisms present. A combination of dehydration and freezing is used in the process known as freeze-drying, whereby solid food remains frozen while its liquid escapes as a vapour. The modern objective of food preservation includes concern for food quality, for economy, and, especially, for convenience in addition to the prevention of spoilage. Colour or appearance, flavour, texture or consistency, and nutritive value are the major quality factors. Most countries have detailed and exacting requirements governing food processing from the standpoint of sanitation and quality, but the extent to which such regulations are enforced varies greatly. Naturally, the emphasis given to quality factors depends somewhat on the level of economic development. any of a number of methods by which food is kept from spoilage after harvest or slaughter. Such practices date to prehistoric times. Among the oldest methods of preservation are drying, refrigeration, and fermentation. Modern methods include canning, pasteurization, freezing, irradiation, and the addition of chemicals. Advances in packaging materials have played an important role in modern food preservation. Additional reading R. MacRae, R.K. Robinson, and M.J. Sadler (eds.), Encyclopaedia of Food Science, Food Technology, and Nutrition, 8 vol. (1993); and Y.H. Hui (ed.), Encyclopedia of Food Science and Technology, 4 vol. (1992), are general works that cover all aspects of the science of food. P. Fellows, Food Processing Technology: Principles and Practices (1988), is an introductory text.Marcus Karel, Owen R. Fennema, and Daryl B. Lund, Physical Principles of Food Preservation (1975), contains a quantitative description of commonly used food-processing operations. S.D. Holdsworth, Aseptic Processing and Packaging of Food Products (1992), is a comprehensive text. James M. Jay, Modern Food Microbiology, 4th ed. (1992), offers an introduction to the role of microorganisms in the food supply, covering the history of food microbiology as a science, the factors that affect microbial growth, the incidence and types of microorganisms found in foods, food preservation, and the part microorganisms play in food spoilage and related diseases. P.R. Hayes, Food Microbiology and Hygiene, 2nd ed. (1992), details the fundamentals of food microbiology and the hygienic aspects of the design and operation of food-processing equipment.C.M.D. Man and A.A. Jones (eds.), Shelf Life Evaluation of Foods (1994), examines various food commodities in terms of their shelf life and discusses methods used to study the shelf life of foods. Theodore P. LaBuza, The Shelf-Life Dating of Foods (1982), a reference book, contains information on the shelf life of numerous food products and provides approaches to mathematical prediction of the shelf life of foods. R. Paul Singh