Modern milling of wheat into flour is accomplished by a fairly complex and highly refined system that uses grooved steel rollers. In what is called the break system, the rollers are set so the space between them is slightly smaller than the width of the kernels, and the rollers rotate at different speeds. When the wheat is fed between them, the rollers flake off the bran layers and germ and crack the endosperm into coarse pieces. By sifting the broken grains, the parts can be separated. Approximately 72% of the wheat kernel can be separated as endosperm and milled into flour. The remaining 28% consists of bran (about 14%), germ (about 3%), and other outer portions called shorts (about 11%).
