By Harold McGee
Tortillas, tamales, and corn chips are made from corn grains that are milled when wet, after they have undergone the preliminary cooking step called nixtamalization. The corn is first cooked in a solution (0.8–5%) of calcium hydroxide, or lime, for a few minutes to an hour, then is left to steep and slowly cool for 8 to 16 hours. During the steeping, the alkalinity softens the hull and cell walls throughout, causes the storage proteins to bond to each other, and breaks apart some of the corn oil into excellent emulsifiers (monoand diglycerides). After steeping, the soaking solution and softened hulls are washed away, and the kernels, including the germ, are then stone ground to produce the dough-like material called masa. Stone grinding cuts the kernels, mashes them, and kneads the mass, mixing together starch, protein, oils, emulsifiers, and cell wall materials, and the lime’s molecule-bridging calcium. With further kneading, this combination develops into a cohesive, plastic dough.