On Food and Cooking

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.