Corn kernels that have been covered with a mixture of water and slaked lime (or wood ash), cooked, then removed from the heat and allowed to soak in the alkaline water. The corn is then thoroughly rinsed and rubbed to remove the lime and any remaining attached hulls. The end result is nixtamal or hominy which, when dried and ground, becomes masa. Nixtamalization dates as far back as 1500 b.c.e. and was used by the ancient Mayans and Aztecs. The process makes the corn easier to grind and enhances its protein and vitamin content, particularly that of niacin. Ground nixtamal is used to make tamale dough and corn tortillas; the whole kernels are used in posole.
From The Food Lover's Companion, Fourth edition by Sharon Tyler Herbst and Ron Herbst. Copyright © 2007, 2001, 1995, 1990 by Barron's Educational Series, Inc.