In almost every country of the world cereal grains form a very important item of food. Rice is the chief dietary staple for almost half of the world’s population and constitutes almost as much as 80% of the calories for most of Asia’s people. Wheat ranks second to rice in worldwide use, and is the principal cereal grain used in European countries. Corn is widely used in Central and South America.
The main cereals consumed in India are rice, wheat and millets (jowar, bajra, ragi, etc.). They are the cheapest sources of calories. In view of the large amounts in which cereals are included in the diet, they form important sources of nutrients in an average Indian diet.
The seed or the kernel of the cereal grain is divided into three parts, the bran, the germ and the endosperm. Cereal grains vary somewhat in composition, the average percentage composition of the whole grain is:
Protein 12%, Fat 2%; Carbohydrates 75%, Water 10%; Minerals and vitamins (especially iron, phosphorus, thiamine) 1%.
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The quality of the protein of cereal grains is somewhat inferior to that of animal sources because some of the essential amino acids are present in less than the needed amounts. Lysine is a limiting amino acid in wheat, rice and corn, while tryptophan and threonine are also present in very small amounts in corn and rice respectively. Rice protein is, however, richer in lysine compared to other cereal proteins-thus rice protein is of a better quality.
The greater part of the minerals, iron and phosphorus and the B-complex vitamins are in the bran and germ of the grain. Consequently, most of the nutrients are lost when cereals are highly milled. Thus the vitamin content of the finished product depends upon the degree of the milling and polishing given to the grain. Highly polished raw rice has very poor content of vitamins. Parboiling rice, on the other hand, contains significant amounts of thiamine.
During the course of parboiling, in which the rice is subjected to steaming in water, the vitamin seeps into the inner portions of the grain so that even on being milled and polished, the grain retains significant amounts of vitamins.
Except yellow maize, which contains some carotene, cereal grains in general do not contain much of Vitamins A and C. Cereal grains themselves are poor sources of calcium and iron. However, ragi is rich in these minerals, especially calcium; and bajra is a good source of iron. Thus the inclusion of these cereals as breakfast cereals may serve as a means by which calcium is included in the diet.