Milling: Conventional and Stone Grinding

Milling is the process of breaking the wheat kernel down into small particles, and sifting the particles to make a flour of the desired qualities. Most flours are refined: that is, they have been sieved to remove the germ and bran layers from the particles of protein- and starch-rich endosperm. Bran and germ are rich in nutrients and flavor, but they go rancid in a few weeks, and interfere physically and chemically with the formation of a continuous, strong gluten; so whole-grain flours make denser, darker breads and pastries. In conventional milling, grooved metal rollers shear open the grain, squeeze out the germ, and scrape the endosperm away to be ground, sieved, and reground until the particles reach the desired size. Stone grinding, which is much rarer, crushes the whole grain more thoroughly before sieving, so that some of the germ and bran end up in even the refined flours. Stone-ground flour is therefore more flavorful than conventionally milled flour, but also has a shorter shelf-life.