FAT AND OIL PROCESSING

method by which animal and plant substances are prepared for eating by humans. The oil and fat products used for edible purposes can be divided into two distinct classes: liquid oils, such as olive oil, peanut oil, soybean oil, or sunflower oil; and plastic fats, such as lard, shortening, butter, and margarine. The physical nature of the fatty material is unimportant for some uses, but the consistency is a matter of consequence for other products. As a dressing on green salads, for example, a liquid oil is used to provide a coating on the ingredients; a plastic fat such as lard or butter would be unsuitable. Spreads for bread, foods that require a highly developed dough structure, or icings and fillings with a plastic structure require plastic fats rather than liquid oils. For reasons related to both history and climate, there are pronounced geographic patterns of consumption of fats and oils. The ancestors of the present inhabitants of central and northern Europe obtained their edible fats almost exclusively from domestic animals. The food habits and the cuisine depended on the availability of plastic fats; and butter, lard, margarine, and shortening continue to be their primary fatty food materials. In contrast, population pressures in the older civilizations of the Orient and the Mediterranean countries of southern Europe, northern Africa, and the Middle East have long since made extensive raising of livestock impractical, necessitating that the edible oils of these regions be derived primarily from intensively cultivated vegetable crops. In the tropics, conditions are relatively unfavourable for livestock but are well suited to culture of a variety of oil-bearing plants, many of which flourish in the wild state. In contrast to most high-population-density tropical areas, cattle abound in India. Clarified butter or ghee is an important item of Indian cookery, and a hydrogenated shortening called vanaspati is designed to reproduce the coarsely crystalline plastic texture of ghee. More than 90 percent of the world production of fats and oils is used in edible products, and the objective of most processing steps is to convert crude fats of low palatability or undesirable physical form into refined products that meet the regional requirements for food fats. The annual consumption of visible fatssuch as lard, butter, shortening, or salad oils that have been separated from the original animal or plant sourceranges from 18 to 25 kilograms (40 to 55 pounds) per person in various highly industrialized European countries to 23 kilograms per person in the United States. For the world as a whole, the average available supply is 10 kilograms per person; and in many areas of South America, Africa, and Southeast Asia, the annual consumption is 5 kilograms or less per person. About 40 percent of the dietary fat in the developed countries comes from isolated fats and oils, with 60 percent obtained from basic foods, whereas in the less developed countries most of the dietary fat is obtained from fruits, cereals, vegetables, dairy products, and meats, and relatively little is consumed in the form of isolated fat products. The quantities of fats and oils in conventional food supplies vary over wide ranges. Most fruits and vegetables have from 0.1 to 2.0 percent fat, with the exception of avocados and olives, which are exceptional in their high fat content. Cereals range from 1 to 7 percent, and nuts may contain as much as 70 percent fat. 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. R. Paul SinghD.K. Salunkhe et al., World Oilseeds: Chemistry, Technology, and Utilization (1992), provides an overview of fat and oil processing. Nuts are treated in Jasper Guy Woodroof, Tree Nuts: Production, Processing, Products, 2nd ed. (1979); and Frederic Rosengarten, Jr., The Book of Edible Nuts (1984). The Editors of the Encyclopdia Britannica