In the production of refined flour, in which both bran and endosperm are lost, the starchy endosperm is separated from the other parts of the kernel by milling through rollers. Following milling, the particles of endosperm (called semolina) are ground to flour and often bleached to imitate natural aging.
The wheat germ, an important part of the grain containing oils and the nutrients in the grain that are responsible for the potential for life and growth in the grain, is removed also. The remaining white starch is relatively devoid of nutritional variety. Any added nutrients, supplied to replace those that are removed during processing, may be unnatural proportions.