How to Nixtamalize Corn at Home, and Where to Buy Cal in the US

Nixtamalization is the single process that separates Mexican corn cooking from everything else done with corn. You simmer dried field corn in water with calcium hydroxide, let it rest, rinse it, and grind it. What comes out is masa: a dough that holds together without gluten, smells of cooked corn rather than cornmeal, and makes a tortilla that puffs. Skip the alkali and you get polenta. There is no way around it.

The chemistry is worth one paragraph because it explains the timings. The alkaline bath dissolves the pericarp — the tough outer skin of the kernel — and rearranges the corn protein so the ground dough becomes cohesive. It also frees the niacin bound up in the grain, which is why a corn-based diet in Mesoamerica never produced the deficiency diseases that corn-based diets elsewhere did. That is a thousand-year-old piece of food technology, and it happens in your pot in about an hour of simmering plus an overnight rest.

The one ingredient you cannot improvise: cal

Cal is calcium hydroxide, also sold as slaked lime, hydrated lime, pickling lime or cal mexicana. It is not the same thing as quicklime (calcium oxide), not the same as agricultural lime (calcium carbonate), and emphatically not the same as the fruit. Buying the wrong one is the most common failure, and the label is how you tell: you want "calcium hydroxide" in the ingredient line and food grade on the package.

Where to buy it: a Mexican grocery store is the reliable answer, and it is usually shelved near the dried corn and the masa harina rather than with the spices. Our directory lists 536 active Mexican and Latin stores in the US, of which 195 are neighborhood groceries and 42 are mercados or meat markets — those are the two formats where cal is nearly always in stock. A full-line Hispanic supermarket will have it too. A conventional American supermarket usually will not, except in canning season, when pickling lime shows up next to the jars.

The ratio and the method

The working ratio is 1 percent cal by weight of dry corn, which is about one teaspoon per pound. More than that and the masa turns slippery and tastes soapy; less and the skins do not let go. Weigh it if you can. This is the step where cooks improvise and then wonder why the tortillas taste of chalk.

Start with two pounds of dried field corn — cacahuazintle for pozole, or a dent corn for tortillas. Rinse it. Bring four quarts of water to a simmer, stir in the cal until the water goes cloudy, add the corn, and hold it at a bare simmer for 45 to 60 minutes. You are not cooking the corn through: you want the kernel still firm at the center, with the skin rubbing off between your fingers. Then take it off the heat and let it stand, covered, 8 to 14 hours. The overnight rest does as much work as the simmer.

Next morning, drain and rinse hard, rubbing handfuls between your palms until the water runs clear and most of the skins are gone. Leave the tip caps on if you are making pozole; take them off for tortillas. What you have now is nixtamal. Ground wet it becomes masa, and masa does not keep: refrigerate it and use it inside two days, or freeze it in flattened portions.

What goes wrong, and what it looks like

Corn that stays hard after the rest was almost certainly old. Dried field corn keeps for years as a grain but nixtamalizes unevenly once it has dried out past a certain point, and no extra simmering fixes it — it just blows the kernels apart at the edges while the center stays chalky. Buy corn from a store that moves it.

Skins that will not release mean either too little cal or too short a rest. Give it the full overnight before you decide anything. Masa that tastes soapy or feels slick means too much cal, and you can wash some of it out with two or three extra rinses, though the flavor never fully comes back. Tortillas that refuse to puff usually mean the masa is too dry or the comal is not hot enough; a drop of water should skitter and vanish, not sit and steam.

Scale matters too. Two pounds of corn yields roughly three pounds of nixtamal and enough masa for about forty tortillas, which is more than a household eats in two days. Halve it the first time. The process does not change, and you will learn more from two careful batches than one large one.

Grinding without a molino

A hand-crank corn mill clamped to a table works and costs less than a stand mixer. A food processor gets you a coarse, slightly gritty masa that is fine for thick antojitos — sopes, gorditas, tlacoyos — and frustrating for thin tortillas. A high-powered blender works in small batches with a splash of the soaking water. What does not work is a dry spice grinder.

If the dough cracks at the edge when you press it, it needs water, a tablespoon at a time. If it sticks to the plastic, it needs a rest, not flour. And if your first batch comes out pale and bland, check the cal: underdosing is the usual culprit, not the corn.

Once you have masa, the obvious places to spend it are Green Chilaquiles from your own fried tortillas and Crispy Potato Tacos, which are both better with fresh masa than with any bagged tortilla.

Where to look near you

Our US directory lists 536 active Mexican and Latin stores across 11 states, plus 630 restaurants. 195 of those stores are neighborhood Mexican groceries and 42 are mercados or meat markets — the two formats most likely to carry the hard-to-find items on this page, because they stock for cooks who need them every week, not for an international aisle.

A few examples from different parts of the country: Numero Uno Market in Los Angeles, Fiestas Market Square in San Antonio, La Michoacana Meat Market in San Antonio, La Michoacana Meat Market in San Antonio, La Michoacana Meat Market in San Antonio, Morelia Supermarket in Chicago. You can browse the whole list by city in our US store directory, and the restaurants in our restaurant directory.