The chemical composition of the cereals varies widely and depends on the environmental conditions, soil, variety and fertilizer.
Wheat has a higher protein content than other cereals: The protein content varies from 7 to 22% depending on the variety. However, because of low availability of some essential amino acids in wheat, its biological value requires addition or supplementation with other amino acids.
Several research efforts have focused in producing different wheat varieties with higher protein and essential fatty acids content.
Carbohydrates are the major chemical composition of the corn. However, the maize corn kernel is more than a rich source of carbohydrate, it is a source of enzymes for the study of biosynthesis and genetic markers for genetic, biochemical, and genetic engineering studies.
The starch granule is formed inside an amyloplast and arranged in an insoluble granule. Starch is the major carbohydrate in the kernel and comprises close to 72% of its dry weight.
Starch also is found in the embryo, bran, and tip cap. Amylose makes up 25-30% of the starch whereas amylopectin composes 70-75% of the starch.
Monosaccharides , such as fructose and glucose are found in equal proportions in the endosperm. Among the disaccharides sucrose is the major sugar in kernels that comprise only 4-8% of kernel dry weight: maltose is also found at less than 0.4% of the kernel dry weight.
The corn bran consists of 70% hemicellulose, 23% cellulose and 0.1% lignin on a dry weight basis.
The protein content of the corn shows that it is poor in essential amino acids such as tryptophan, lysine and threonine, valine and sulfur amino acids.
The corn has only 4.4% oil (dry basis), but the amount of corn oil production is enormous, even though it is not considered as an oil seeds crop.
Triglycerides are the major composition (98.8%) of the refined commercial corn oil.
Corn oil is very stable compared with other seed oils owing to its flow level of linolenic acid and the presence of natural antioxidant.
The composition of rice and its fraction depends on the cultivars, environmental conditions and processing. The rice components distributes differently in aleurone, embryo and other parts of the grain.
The average brown rice protein content ranges from 4.3 to 18.3% with a mean value of 9.2%.
Protein is the second most important rice component after carbohydrates.
The ouster tissue of the rice grain are rich in water soluble proteins (albumin) and also salt soluble proteins (globulin), but the endosperm is rich in glutelin.
The milling fraction of the rice grain has a limited prolamin (alcohol free proteins), and the non-protein nitrogen (NPN) of the rice is about 2 -4%.
Rice starch is composed of linear fraction - amylose and branched fraction -amylopectin – that is a major factor in the eating and cooking quality of the rice.
Chemical Composition of Cereals
