Nixtamal, the Chemistry That Made Mesoamerica

Dried maize is a difficult food. The kernel is armoured in a tough pericarp, its protein is short on lysine and tryptophan, and — the part that matters most — its niacin, vitamin B3, is chemically bound up in a form the human gut cannot release. Live on untreated corn and you will eventually get pellagra: dermatitis, diarrhoea, dementia, death.

Mesoamerican cooks solved this at least 3,500 years ago, and the solution is a pot of water, some maize, and a handful of wood ash or slaked lime.

What the alkali does

Simmer maize in an alkaline solution — calcium hydroxide from burnt limestone, or potash from hardwood ash — and let it steep overnight. Four things happen at once:

1. The hull comes off. The pericarp loosens and rubs away between your palms, which is why nixtamalised corn feels slippery.
2. The niacin is freed. The bound niacytin is hydrolysed into a form the body can absorb. This alone is the difference between a staple and a slow poison.
3. The protein improves. The amino-acid balance shifts, and calcium from the lime is absorbed into the grain — a maize tortilla is a meaningful source of dietary calcium, which raw maize is not.
4. The starch and protein reorganise. The kernel becomes grindable into a dough that coheres — masa — instead of a dry meal that falls apart. Corn has no gluten; nixtamalisation is what gives masa its plasticity.

The word is Nahuatl: nextli, ashes, and tamalli, dough. The technique travelled with maize into the American South, where hominy and grits are the same chemistry, and famously did not travel to Europe. Maize crossed the Atlantic in the sixteenth century as a crop; the processing stayed behind. Pellagra epidemics followed maize into northern Italy, Romania, Egypt and the American South, and were not correctly explained until Joseph Goldberger’s work in the 1910s and 1920s — four centuries of a preventable disease caused by importing an ingredient without its method.

What it tastes like

Anyone who has eaten a tortilla made from fresh masa next to one made from industrial masa harina knows the difference is not subtle. Fresh nixtamal is sweet, faintly limey, intensely corn — the flavour supermarket tortillas gesture at. The gap is time: masa harina is nixtamal that has been dried and milled, which costs it most of its aroma.

The family it holds up

Almost everything on a Mexican table descends from masa:

• Tortillas, pressed and cooked on a comal until they puff.
• Tamales, masa beaten with lard until a spoonful floats in water, then wrapped in corn husk or banana leaf and steamed.
• Pupusas in El Salvador, thicker and stuffed before cooking.
• Sopes, huaraches, tlacoyos, gorditas — the same dough, different geometry, different degree of enclosure.
• Pozole, where the nixtamal is never ground at all: the whole kernels are simmered until they burst open into flowers.

Whole nixtamal is also what “hominy” means, which makes grits, pozole and Southern hominy the same preparation with three names and three histories.

Doing it at home

Food-grade calcium hydroxide — cal, pickling lime — is cheap and widely sold. Use roughly 1% of the maize’s weight, simmer twenty minutes, steep overnight, rinse and rub. The corn matters more than the technique: field corn or heirloom landrace maize, not sweetcorn, which is bred for sugar and will give you nothing.

Grind it wet. A blender will not do it — you want a stone mill or a metate, or you buy the masa from someone who has one, which is what most Mexican cooks sensibly do.