玉米粉（Masa）

No. Masa is made from maize cooked in lime water (nixtamalized); cornmeal is simply ground raw maize. Only masa can form a tortilla dough.

Yes, pure masa harina made only from maize and lime is naturally gluten-free. People with coeliac disease should still choose products labelled gluten-free (in the US and EU this means under 20 parts per million of gluten), because of possible cross-contact in mills.

Lime (calcium hydroxide) loosens the hull, softens the kernel, lets the dough hold together, adds calcium, releases niacin and gives masa its typical flavour.

About one to three days in the refrigerator, or a few months frozen. Dry masa harina lasts several months in a cool, dry place.

Mexico is by far the largest producer and consumer, followed by the United States and Central America. Europe and Asia-Oceania are the fastest-growing new markets.

Mexico's Gruma, owner of Maseca and Mission, is the largest producer of corn flour and tortillas globally.

Nejayote is the alkaline cooking liquor drained off after nixtamalization. It has a pH of about 11–12 and a very high organic load, so it must be treated, reused or turned into by-products rather than discharged.

Dent and floury field corn work best. Flint corn can be used with longer cooking, while sweet corn and popcorn are poorly suited.

Maseca is a brand. It is Gruma's masa harina, the best-known nixtamalized corn flour in the world.

Tortilla chips are cut from sheeted masa, usually toasted and then fried. Corn chips are made from a coarser masa extruded straight into hot oil, so they are thicker and crunchier.

About 1 to 1.3 parts warm water for every part of masa harina by weight, which gives a dough of 50–60% moisture. Brands differ, so follow the pack and adjust until the dough feels soft but not sticky.

Traditional lime cooking yields about 87–89 kg of masa harina from 100 kg of maize. The rest is lost as hull, starch and germ solids in the cooking and wash water.

Plain masa and corn tortillas are a whole-grain-based, gluten-free food with useful fibre, and lime cooking gives them far more calcium and usable niacin than plain maize. Fried products such as tortilla chips are much higher in fat and salt.

Maize travelled around the world after 1492, but the lime-cooking method did not. People who lived mainly on untreated maize lacked usable niacin and developed pellagra, which stayed common in parts of southern Europe and the US South until well into the 20^th century.