STRUCTURE OF RICE AND WHEAT
The overall structure of all cereal grains is basically similar. Rice grains resemble wheat but is smaller than that of wheat. It is flattened laterally and has no ventral furrow.
Wheat cereal grains are composed of an outer bran coat, a germ and a starchy endosperm.
Source: Sumati Mudambi, R and Shalini, M. Rao 1989 Food Science. New Age International (P) Publishers Ltd, Chennai.
The longitudinal structure of wheat grain depicting the various layers is represented diagrammatically in fig.
Bran is the outer layer of the kernel and constitutes 5 percent of the kernel. During milling the bran is discarded. Bran is rich in fibre and minerals. It is also a good source of thiamine and riboflavin.
This is located just under the bran, which is rich in protein, phosphorus and thiamin and contains moderate amounts of fat. The aleurone layer makes up about 8 percent of the whole kernel. This layer is lost in the milling process along with bran.
This is the large central part of the kernel and constitutes 84 - 85 percent of the kernel. The endosperm cell consists mainly of starch and protein and little mineral matter and fibre and only half a trace of fat. The vitamin content of the endosperm is low.
This is a small structure at the lower end of the kernel and is separated from the endosperm by the scutellum. It makes up 2 - 3 percent of the whole kernel. It is rich in protein, fat, vitamins and minerals.The germ serves as a store of nutrients for the seed when it germinates. During milling some of the germ is lost along with the bran and aleurone layer.