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grain, in agriculture
See N. L. Kent, Technology of Cereals (1983); Y. Pomerantz, Modern Cereal Science and Technology (1987).
grain, in weights and measures
an obsolete unit of weight used in Russian pharmaceutical practice before the introduction of metric units of measure; one grain equaled 62.2 mg. In the British system the grain—commercial, apothecaries’ and troy (used in weighing precious metals)—is equal to 64.8 mg.
(1) The fruit of cereal grasses and the seed of legumes.
(2) The product of grain production. Grain is one of the principal human food products, a raw material for the flour, groats, beer, starch, alcohol, and mixed feed industries, and a concentrated feed for farm animals. The products of grain processing are used in the baking, macaroni, and confectionery industries. Grain is the most important part of the state food reserves and an export.
The grain of cereal grasses is a dry, monospermous fruit (caryopsis) that is glabrous in wheat, rye, corn, and the naked forms of barley and oats and tunicate (covered with flowering husks) in oats, barley, rice, and millet. The heaviest part of the grain is the endosperm, from which the most valuable part of flour is obtained during milling. Most of the cells of the grain are filled with starch and protein. The outermost layer of the endosperm—the aleurone layer—is rich in proteins and fat. The layer next to the aleurone contains the most protein. During graded milling the aleurone layer is separated from the grain and discarded, because the human organism does not digest it well. Depending on the dimensions, shape, and location of the starch grains and on the properties and distribution of proteins, the grain may be vitreous, semivitreous, or mealy.
In the lower part of the grain is the seed, the embryo of the future plant. It contains a great deal of protein, fat, sugars, vitamins, and enzymes. During graded milling the seed is removed because it is difficult to crush and because the fat contained in it turns rancid easily and ruins the flour during storage. The exterior of the grain is covered with the fruit and seed shells, which are generally discarded during graded milling. In wheat grain, the weight ratio of the endosperm (in percentages) is 81.1–84.2, of the aleurone layer, 6.8–8.6, of the seed, 1.4–3.2, and of the shells, 3.1–5.6. In oats, the endosperm is 51–61 percent of the total weight of the grain, the aleurone layer, 4–6 percent, the seed, 3–4 percent, the shells, 2–4 percent, and the flowering husks, 20–40 percent.
The mature grain of legumes has no endosperm. It is covered with a seed membrane (skin), under which lies the seed, which consists of meaty cotyledons and the embryonic stock, root, and plumule. In the most common legumes, the shell is 6.4–11 percent of the total weight of the grain, the cotyledons, 87.2–92.5 percent, and the root, stock, and plumule, 1.1–2.5 percent. (See Table 1 for the average chemical composition of grains, given a moisture level of 14 percent.)
|Table 1. Chemical composition of grains (in percent)|
|soft||120||1 7||687||20||1 6|
|Peas||23 4||2 4||53.1||4.7||2.4|
The basic component of grain carbohydrates is starch, whose hydrolysis is very important in the preparation of dough. Cellulose and hemicellulose are part of the composition of the cell walls. Maltose, glucose, and fructose are among the sugars found in grains. The proteins in cereal grass grains are primarily prolamins and glutelins. The principal proteins in wheat are gliadin and glutenin, which form gluten, whose quantity and quality determine the elasticity of the dough and the porosity and volume of the bread. The gluten in rye (which is separated out under special conditions) and of barley (which is not contained in all grades of grain) does not have the valuable physical properties of wheat gluten. The proteins in legumes consist primarily of globulins and a small number of albumins. They are richer than the proteins of the cereal grasses. In most grains, the largest quantity of fats (primarily unsaturated fatty acids) is contained in the seed, but in peanuts and soybeans the fats are concentrated in the cotyledons. Grain ash contains phosphorus, potassium, magnesium, calcium, silicon, and other elements (in the form of oxides).
Enzymes are concentrated primarily in the embryo. The most important of them are α-amylase, β-amylase, orglucosidase (maltase), β-fructofuranosidase (invertase), lipase, protease, and catalase. Grain contains numerous vitamins, which are concentrated in the seed and the peripheral layers. Among them are thiamine (B1), riboflavin (B2), pyridoxine (B6), nicotinamide (PP), ascorbic acid (C), and, in germinated grain only, pantothenic acid and the pigment carotene, the source of retinol (vitamin A).
The quality of grain is evaluated on the basis of its freshness, color, odor, taste, acidity, weediness, moisture, character (weight of 1 liter), weight of 1,000 grains, and the cleanliness of the grain stores, which should be free of pests and diseases. In production evaluation (flour milling and baking), vitreousness, ash content, and protein content are often determined. Experimental bread is baked from flour and evaluated (volume of bread produced per 100 g flour and stability of the shape of bread). In the USSR the quality of grain is evaluated according to state standards, and standardized conditions have been established for processing grain. The quality of export grain is graded according to technical specifications.
REFERENCESKretovich, V. L. Biokhimiia Zerna i Khleba. Moscow, 1958.
Koz’mina, N. P.Zerno i produkty ego pererabotki. Moscow, 1961.
Kazakov, E. D.Zernovedenie s osnovamirastenievodstva. Moscow, 1965.
Spravochnik po kachestvu zerna i produktov ego pererabotki. [Compiled by V. T. Tevosian, B. M. Mashkov, and F. I. Biriukov.] Moscow, 1965.
Koz’mina, N. P. Zerno. Moscow, 1969.
E. D. KAZAKOV
a pattern on leather. In manufacturing leather, irregularities remain on the surface of the corium after the removal of the epidermis (which extends somewhat into the corium). These irregularities, together with pores, form the grain. The skin of each species of animal has its characteristic grain, making it possible to distinguish leathers. An artificial grain can be given by embossing a pattern on the leather.
What does it mean when you dream about grain?
Grain represents an opulent harvest and is often symbolic of a good life.
["Pictorial Information Systems", S.K. Chang et al eds, Springer 1980].