Traditional Tortilla Making

The mother is grinding the maize with a stone mano and metate as the elder daughter pats the dough into tortillas.
The traditional tortilla has been made of corn or maize since Pre-Columbian times. It is made by curing maize in lime water in a process known as nixtamalization which causes the skin of the corn kernels to peel off (the waste material is typically fed to poultry), then grinding and pre-cooking it, kneading it into a dough called masa nixtamalera, pressing it flat into thin patties, and cooking it on a very hot comal (originally a flat terra cotta griddle, now usually made instead of light sheet-metal).

Soaking the maize in lime water is important because it liberates the vitamin niacin and the amino acid tryptophan. When maize was brought back to Europe, Africa and Asia from the New World, people left out this crucial step. People whose diet consisted mostly of corn meal often became sick - because of the lack of niacin and tryptophan - with the disease pellagra, which was common in Spain, Northern Italy, and the southern United States.

In Mexico, particularly in the towns and cities, corn tortillas are often made nowadays by machine and are very thin and uniform, but in many places in the country they are still made by hand, even when the nixtamal is ground into masa by machine. In Belize, El Salvador, Guatemala, or Honduras they are still often made by hand and are thicker. Corn tortillas are customarily served and eaten warm; when cool, they often acquire a rubbery texture.