Structure and Composition of Cereal Grains and Legumes

Abstract

Cereals are monocotyledonous plants that belong to the grass family. Based on botanists’ approximation, there are about 350,000 plant species, of which about 195,000 species are economically important flowering plants. Nearly 50 species are cultivated worldwide and as few as 17 species provide 90% of human food supply and occupy about 75% of the total tilled land on earth. They consist of wheat, rice, corn, potato, barley, sweet potato, cassava, soybean, oat, sorghum, millet, rye, peanut, field bean, pea, banana, and coconut. The cereal grains such as wheat, rice, corn, barley, oat, rye, sorghum, and millet provide 50% of the food energy and 50% of the protein consumed on earth. Wheat, rice, and corn together make up three-fourths of the world’s grain production. In general, cereal grains have been considered as the source of carbohydrates to supply food energy to the diet. Cereal grains, especially rice and wheat, provide the bulk of energy consumed on earth (Stoskopf, 1985). The cereal crops that are grown for their edible fruit are generally called grain, but botanically referred to as caryopsis. The cereal seed consists of two major components, the endosperm and embryo or germ. The endosperm encompass the bulk of the seed and is the energy source of stored food. An outer wall called the pericarp that develops from the ovary wall encases the endosperm. A semipermeable layer under the pericarp, which is called testa, surrounds the embryo and is derived from the inner ovary wall. The testa is permeable to water, but not to dissolved salts, and is important for germination. The third layer, which is called aleurone, contains thick-walled cells that are free of starch. The pericarp, testa, and aleurone layer are collectively called the bran. The legumes such as chickpea, black gram, mung bean, and pigeon pea, have an estimated 16,000–19,000 species in 750 genera. Asia ranks first both in area harvested