Nixtamalization — cal treatment of dried maize

Pre-Columbian Mesoamerica; earliest evidence circa 1500–1200 BCE in the Soconusco region of southern Mexico and Guatemala. The Aztec (Mexica) term is nextamalli (from nextli, lime ashes, and tamalli, unformed corn dough).

Nixtamalization is the pre-Columbian process of cooking dried maize kernels in an alkaline solution of water and calcium hydroxide (cal, slaked lime — not citrus) to transform the grain chemically, nutritionally, and structurally. The process liberates niacin (vitamin B3) bound in the maize pericarp, making it bioavailable and preventing pellagra. Without nixtamalization, populations eating maize as a staple suffer niacin deficiency; this is why non-nixtamalized maize diets in colonial Europe caused epidemic pellagra. The chemistry: cal raises the pH of the cooking water to approximately 11–12, breaking the hemicellulose bonds in the pericarp (outer skin), gelatinising the starch partially, and cross-linking proteins to create a pliable, extensible masa. The distinctive flavour — earthy, mineral, complex — comes from the Maillard products of partially gelatinised starch interacting with the alkaline minerals. Masa Harina (Maseca brand) is pre-nixtamalized dried masa flour; fresh nixtamal ground on a stone metate or electric mill produces a masa of categorically superior flavour and texture.

Properly nixtamalized masa has a complex minerality, faint earthiness, and a sweetness from partially gelatinised starch that is entirely absent from non-nixtamalized maize flour. This flavour is the foundation of all Mexican corn-based cuisine.