To understand how processing affects the nutritional value of grains, an understanding of where nutrients are located in the grain kernel is required. Although there are slight differences between grains, the distribution of nutrients in the grain kernel is essentially the same for all grains.

The seed coat, consists of a layer of epidermis and several thin inner layers, which together are a few cells thick. Underneath the seed coat, one to four cells thick, is the aleurone layer. Loaded with fibres, minerals, oil, protein and vitamins, these layers are collectively referred to as bran.

Bran surrounds the endosperm, which stores most of the protein and carbohydrate, and makes up most of the kernel’s volume. Against the endosperm is the scutellum, which absorbs, digests and transfers food from the endosperm to the embryo, or germ, found at the base of the grain. The germ, the grain’s smallest part, is the most nutritious part of the grain, as it concentrates the B vitamins, minerals, and vitamin E.