CEREAL PROCESSING

treatment of cereals and other plants to prepare their starch for human food, animal feed, or industrial use. Cereals, or grains, are members of the grass family cultivated primarily for their starchy seeds (technically, dry fruits). Wheat, rice, corn (maize), rye, oats, barley, sorghum, and some of the millets are common cereals; their composition is shown in the Table. Starch, a carbohydrate stored in most plants, is a major constituent of the average human diet, providing a low-cost energy source with good keeping qualities. Cereals are high in starch, which may be used in pure or flour form. Starches are also obtained from such root sources as potatoes and from the pith of tropical palm trees. Various starches are used commercially in food processing and in the manufacture of laundering preparations, paper, textiles, adhesives, explosives, and cosmetics. This article treats the processing and utilization of the major cerealswheat, rice, barley, rye, oats, corn, sorghum, millet, and buckwheat; of important starchy foods consumed in certain countries instead of cereals, including potatoes and cassava; and of soybeans, legumes widely used in the bakery industry. Wheat species are treated in detail, other cereals in a more general way. 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 SinghThe composition, processing, and uses of cereals and other starch products are discussed in Giuseppe Fabriani and Claudia Lintas (eds.), Durum Wheat: Chemistry and Technology (1988); Y. Pomeranz (ed.), Wheat: Chemistry and Technology, 3rd ed., 2 vol. (1988), and Wheat Is Unique: Structure, Composition, Processing, End-Use Properties, and Products (1989); Y. Pomeranz, Industrial Uses of Cereals (1973), and Modern Cereal Science and Technology (1987); Advances in Cereal Science and Technology (biennial); Stanley A. Watson and Paul E. Ramstad (eds.), Corn: Chemistry and Technology (1987); Bienvenido O. Juliano (ed.), Rice: Chemistry and Technology, 2nd ed. (1985); Ruth H. Matthews (ed.), Legumes: Chemistry, Technology, and Human Nutrition (1989); Allan K. Smith and Sidney J. Circle (eds.), Soybeans: Chemistry and Technology, vol. 1, Proteins, rev. ed. (1978); Harry E. Snyder and T.W. Kwon, Soybean Utilization (1987); and Soy Protein Council, Soy Protein Products: Characteristics, Nutritional Aspects, and Utilization (1987).Some starch products are treated in R. Gordon Booth (ed.), Snack Food (1990), discussing the snack food industry in the United States and Great Britain; and Robert B. Fast and Elwood F. Caldwell (eds.), Breakfast Cereals, and How They Are Made (1990). The Editors of the Encyclopdia Britannica Nonwheat cereals Barley Most of the barley grown in the world is used for animal feed, but a special pure barley is the source of malt for beer production. Barley is also used in the manufacture of vinegar, malt extract, some milk-type beverages, and certain breakfast foods. In addition, in flaked form it is employed in some sections of the brewing industry, and pearl barley (skins removed by emery friction) is used in various cooked foods. Figure 4: (Left) The barley spike, with rows of barley florets. (Right) Cross section of the Barley (see Figure 4) can be cultivated on poorer soil and at lower temperatures than wheat. An important characteristic in barley is winterhardiness, which involves the ability to modify or withstand many types of stresses, particularly that of frost. However, barley is subject to many of the diseases and pests that affect wheat. The use of barley in animal feed is increasing; it has been a basic ingredient of pig foods for years and is increasingly used for cattle feed. Its use in poultry foods has decreased because it has a lower starch equivalent when compared with wheat or corn and thus provides a lower-energy ration, unsuitable in modern poultry production. Barley vitamin content is similar to that of wheat. Corn Figure 5: The outer layers and internal structures of a kernel of corn. Corn, or maize, a cereal cultivated in most warm areas of the world, has many varieties. The United States, the principal producer of corn, cultivates two main commercial types, Zea indurata (flint corn) and Z. indentata (dent corn). The plant grows to a height of about three metres or more. The corn kernel (shown in Figure 5) is large for a cereal, with a high embryo content, and corn oil extracted from the germ is commercially valuable. The microscopic appearance of the starch is distinctive, and the principal protein in ordinary corn is the prolamin zein, constituting half of the total protein. On hydrolysis zein yields only very small amounts of tryptophan or lysine, making it low in biological value. The proteins of corn, like those of most cereals other than wheat, do not provide an elastic gluten. Much of the corn is wet-processed to produce corn flour, widely used in cooking (see below Starch products: Cornstarch). Corn, dry-milled as grits or as meal or turned into flaked corn with some of its starch partially gelatinized, is a popular component in compounded animal feedstuffs. In dry-milled form it is also the basis of human food throughout large areas of Africa and South America. Its nutritive value is limited by its low lysine content. Much recent research has involved development of a corn with higher lysine content. Mutants have been produced containing much less zein but possessing protein with higher than normal lysine and tryptophan contents, sometimes increased as high as 50 percent. These corns, called Opaque-2 and Floury-2, possess certain drawbacks. They are generally lower in yield than dent hybrids, are subject to more kernel damage when combine-harvested, and may be more difficult to process. Nevertheless, these new hybrid corns are expected to become widely cultivated, and the principles involved in their production may also be applied to sorghum, wheat, and rice. Corn is popular for use in breakfast foods.