Nixtamalization is a process discovered by the Aztec and Maya civilizations of Mesoamerica (see central America), but not by the Inca in S. America, which transformed the maize which they had already domesticated into a truly superior foodstuff.
It is a complex process that starts with soaking the ripe maize grains and then cooking them with lime or wood ashes. This enables the transparent skin on the grain, the pericarp, to be removed, and of course makes the grain easier to grind. But the major contribution of nixtamalization is that it much enhances the protein value of the maize for human beings. So superior is nixtamalized maize to the unprocessed kind that it is tempting to see the rise of Mesoamerican civilization as a consequence of this invention, without which the peoples of Mexico and their southern neighbours would have remained forever on the village level. When and where this discovery was made is unknown, but typical household equipment for making nixtamal out of maize is known on the south coast of Guatemala at dates between 1500 and