Tortillas are unleavened flat breads made with corn or wheat flour, water, and salt. They are widely used throughout Latin America, but are most closely associated with Mexican cuisine, where they make up the bulk of nutritional intake for impoverished Mexicans. Tortillas are used in dishes like tacos, burritos, or quesadillas, and when they get stale they are fried and used for chips, in chilaquiles or in tortilla soup, also known as Sopa Azteca. The term is also used in Spain to refer to a type of flat omelet, and the root for both words is the same: torta, or little cake.
The Amerindians were the first people to work with corn, and they have been making tortillas for centuries in the traditional way. Flour tortillas were a later invention, and are not widespread in Mexico, because corn is more nutritious and usually cheaper to obtain. Although tortilla making machines are used for commercial production, homemade tortillas are widely available in Mexico and in other parts of the world with large immigrant communities. Homemade tortillas tend to be more flexible, with a more intense corn flavor that some people find preferable.
To make tortillas, a cook starts with whole dried corn and boils it in a pot with water and calcium hydroxide, colloquially called slaked lime or tequesquite in Mexico. Calcium hydroxide is an alkaline mineral that loosens the skins of the corn and releases nutrients held inside. This is one of the reasons that the tortilla is so nutritious: the slaked lime releases bound nutrients so that the consumer can benefit from them. Then, the cook grinds the mixture with a stone, periodically adding water so that the mixture turns into a smooth paste which can be formed into balls. Traditionally, the balls are hand formed into perfectly even tortillas, which are ready to cook on the griddle.
Many home cooks making tortillas use a tortilla press, a device which is designed to produce even, round tortillas by compressing them between two heavy metal dies. Commercially manufactured tortillas are often made on huge assembly lines with cutters and rollers, which can produce tortillas even more quickly than a tortilla press. When packaging tortillas for shipping, they are usually frozen so that they stay fresh. Mexico exports tortillas all over the world, but the market within Mexico for packaged tortillas is actually relatively small, because cooks find it cheaper to make tortillas at home and they prefer the home made flavor.
In 2006, concerns were raised about a nutritional crisis in Mexico due to climbing corn prices, which were in turn affecting impoverished Mexican families. In early 2007, the Mexican government began to think about ways to avert it, including government subsidies for corn. The loss of traditional tortillas would be devastating to impoverished Mexican families who rely on them for nutrition, but also to Mexican culture in general, because the tortilla is an essential component of Mexican cuisine.