A whole grain consists of 4 main parts, which include the husk (hull), bran, germ (embryo), and endosperm. The husk or hull is the outer covering that millers remove before processing grain into foods or food ingredients. All types of grains with the husk removed are referred to as whole grains.
The bran consists of the layers under the husk that protect the inner substance of the grain kernel. Bran layers contain high levels of nutrients, such as fiber, vitamins and minerals.
The germ, which is also referred to as the embryo, is the material located at the bottom center of the kernel just above the stalk and is surrounded by the layers of bran wrapped around it. Since the germ is very perishable, turning rancid if the kernel is broken open, it is quickly removed and not ground into flour as the meal is processed.
Endosperm makes up the majority of the substance in a kernel of grain and consists primarily of starchy carbohydrates. It surrounds the germ and provides nourishment to the germ as the kernel grows.