Starch content in cereal grains

Cereal grains have been the principal component of human diet for thousands of years and have played a major role in shaping human civilization. Around the world, rice, wheat, and maize, and to a lesser extent, sorghum and millets are important staples critical to daily survival of billions of people. The chemical composition of cereal grains (moisture 11–14%) is characterized by the high content of carbohydrates.

The major carbohydrate is starch (55–70%) followed by minor constituents such as arabinoxylans (1.5–8%), b -glucans (0.5–7%), sugars (~3%), cellulose (~2.5%), and glucofructans (~1%).

Cereal grains supply most of their food energy as starch. Cereal and grain legumes together may contribute 70% to 90% of the calories in the daily diet and a almost similar of dietary protein.

Starch occurs only in the endosperm and is present in granular form. Endosperm is the largest part of grain. It composed mainly of starch. Outer layer of endosperm is called the aleurone layer. Starch consists of the two water-insoluble homoglucans amylose and amylopectin. Cereal starches are typically composed of 25–28% amylose and 72–75% amylopectin.

Mutant genotypes may have an altered amylose/amylopectin ratio. Amylose is a predominantly linear molecule linked by α-1, 4 bonds and amylopectin is a highly branched polymer with branch points linked by α-1, 6 bonds. It is the ratio of amylose to amylopectin and fine structure of these polymers that give native starch its distinctive properties

Wheat has the larger, lenticular shaped A-starch granules and the smaller, spherical B-starch granules. A-starch granule type makes up 90% of the weight but less than 20% of the number of starch granules in wheat and some other cereals such as maize, and sorghum.
Starch content in cereal grains