The bran consist of several different layers. It acts as a barrier to protect the grain. The outer layers, or pericarp are fibrous and waxy and create a protective barrier against water and mould penetration.
The aleurone layer lies between the bran and the floury part of the grain. The layer encases the endosperm and part of the embryo. The bran, outer portion of grain contains a small amount of protein, large quantities of the three major B-vitamins, trace minerals and dietary fiber – primarily insoluble.
In some milling processes the aleurone layer is removed as part of the bran while in others it is retained by the endosperm.
In order to protect the grain and endosperm, the bran comprises water-insoluble fiber. Its chemical composition is complex, but it contains essentially, cellulose - a polymer based on glucose – and pentosans, polymers based on xylose and arabinose, which are tightly bound to protein.
Bran component of grain
