Wheat grain
Bread wheat species are derived from a hermaphroditic annual grass in the Gramineae (also known as the Poaceae) family, and in the genus Triticum. They are native to the Middle East but adapted to temperate climates. The most common species used in agriculture is T. aestivum (formerly known as T. vulgare).

The wheat berry, normally referred to as the grain or kernel, is quite a complex entity. It has three main parts, each having further discrete features:

Bran
The term bran refers to the woody materials which make up the protective husk of the grain. These comprise the 5 layers which surround the whole grain plus 2 layers which only partially cover the germ. Bran constitutes about 13% of the dry weight of the grain, and is rich in protein.

The beard or 'awn' consists of hairs of varying sizes (only just discernible to the naked eye) emerging from the upper part of the kernel.

Germ
The germ or embryo plant constitutes about 2% of the grain. It includes the scutellum (L. scutum ‘shield’) layers (covering the plumule and radicle (rudimentary leaves and root)) which contain most of the vitamins found in the grain. It is rich in certain vitamins, protein and oil, and is a source of enzymes including α-amylase and β-amylase.

Endosperm
This forms about 85% of the grain. It consists mainly of cells packed with grains of starch (formed from the polysaccharides amylopectin and amylose). The cell walls are made up from cellulose microfibrils bonded by pentosans (non-starch polysaccharides). The proteins required for gluten formation in dough, glutenin and gliadin, are deposited in protein storage bodies found in the spaces between the cells of the developing endosperm.

Grain constituents

The exact constituents of a sample of grain are dependent on the variety concerned and the growing conditions. Characteristics which distinguish the different varieties include amylase activity (see under Diastasis), protein quality and quantity, hardness and moisture content. Prior to use, the level of enzyme activity associated with germination may be determined, and its physical condition checked.

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