All cereal grains comprise three parts: the bran (a layered protective outer coat), the germ (the embryonic part of the plant), and the endosperm (the large starchy part, containing some protein). Except for two amino acids, lysine and tryptophan, most cereals contain the essential amino acids required by humans, as well as vitamins and minerals.
When they are consumed with other foods that can supplement the nutritional elements that are low in cereals, the minimum dietary requirements may be met or nearly met. Research in cereal genetics may be expected to produce hybrid cereals that will be complete or nearly complete foods, containing more of the nutritional elements required by humans. A composite proximate analysis of cereal grains indicates that they have a protein content about 11%, fat about 3%, moisture about 12%, carbohydrate about 68%, and fiber about 6%.
On a world basis, rice is the most important cereal, being produced for human food in the largest amount, while in the United States, corn is produced in the largest amount, although it is for animal food and other products as well as for human food. The grain grown in the largest quantity for human food use in the United States is wheat.
For most food uses of cereals, the bran and the germ are removed: the bran, because it is indigestible by humans and because of its adverse effect on the appearance and on some functional properties if flour, and some germ, because of its high content, which may subsequently become rancid. The germ is used to produce oil (e.g., corn oil). The bran goes mainly to feed animals. However, with dietary guidelines recommending more fiber, a growing amount of bran is being used in the production of breakfast cereals, bakery products, and other human foods.
