The main components of cereal grains are the hull, pericarp, testa, aleuron, endosperm and germ. The starchy endosperm constitutes about 80-85% of the weight of the whole kernel, the germ 2-3% and the outer layers about 10-15%. Dietary fibre is located mainly in the outer layers of the kernel, especially in the bran.
Before rye grains can be used in food production, the outer part of the grain, the hull, must be removed. After hulling, which generally occurs during threshing, the grains are used as whole, cracked or flaked, or they are ground to produce flour. In bread making, rye protein do not form gluten, and the cell wall polysaccharides in rye have a profound effect on the rheological properties of dough and bread.
Microscopic picture of Rye Kernel