By Harold McGee
Wheat grain and flour. Left: The wheat kernel before milling. Its actual length is about a quarter of an inch/6 mm. Upper right: Soft wheat flour. The protein in this kind of wheat comes in thin, weak sections interrupted by starch granules and air pockets. When milled, it produces small, fine particles. Soft flour makes a weak gluten and is preferred for tender pastries and cakes. Lower right: Hard wheat flour. The protein matrix in hard wheat endosperm is strong enough to break off in chunks during milling. Hard flours make strong gluten and are preferred for most bread making.