Nixtamalization: How Lime Turns Corn into Masa
Nixtamalization is the traditional process of cooking dried corn in an alkaline solution, usually water with calcium hydroxide (slaked lime, called cal in Mexico), then soaking it for hours. The treated corn, nixtamal, is rinsed and ground into masa for tortillas, tamales, pupusas and sopes. The word comes from Nahuatl, the language of the Aztecs: nextli (ashes) plus tamalli (corn dough).
It has been practised in Mesoamerica for thousands of years, and it transforms corn's texture, flavour and nutrition.
How it's done
A typical home method:
- Dissolve about 1% of the corn's weight in cal in plenty of water (around 10 g cal per 1 kg dried corn).
- Add dried field corn and simmer for 30–60 minutes, until the hulls slip off when rubbed.
- Turn off the heat and let the corn steep in the liquid for 8–16 hours.
- Drain and rinse well, rubbing to remove loosened hulls.
- Grind the wet nixtamal into masa.
Cal is a strong alkali, around pH 12 in solution. Use food-grade cal, a non-reactive pot (stainless or enamel, not aluminum), and avoid contact with eyes and skin.
What the alkali does
Loosens the hull. The high pH breaks down hemicellulose in the tough outer layer (pericarp), so it slips off. Some of that dissolved material becomes natural gums that help bind the dough.
Makes dough possible. Partial gelatinization of starch, plus changes to the corn's proteins, let ground nixtamal form a pliable dough. Untreated cornmeal just crumbles.
Frees niacin. Much of the niacin (vitamin B3) in corn is chemically bound and unavailable to the body. The alkaline treatment releases it. Where corn became a staple without nixtamalization, as in parts of Europe and the American South, the niacin-deficiency disease pellagra became widespread.
Adds calcium. Masa absorbs calcium from the cal, making tortillas a meaningful source.
Creates flavour and colour. The alkaline conditions produce the distinctive aroma of fresh corn tortillas and turn white corn slightly yellow.
Nixtamal products
| Product | What it is |
|---|---|
| Nixtamal | Treated whole kernels, before grinding |
| Masa | Fresh dough ground from nixtamal |
| Masa harina | Dried, powdered masa; just add water |
| Hominy | Whole nixtamalized kernels, often canned |
| Grits (some) | Traditionally coarsely ground hominy |
Tips
- Use dried field or dent corn; sweet corn won't work.
- Rinse thoroughly, or masa can taste bitter and soapy from excess cal.
- Fresh masa sours within a day or two; refrigerate it.
Questions
Why can't I make tortillas with regular cornmeal?
Untreated cornmeal won't form a cohesive dough; it crumbles when flattened. Nixtamalization changes the corn's starch and proteins and releases gums from the hull, which let masa hold together and roll out.
What is cal?
Cal is food-grade calcium hydroxide, also called slaked lime or pickling lime. It's a strong alkali, so it should be handled carefully and kept away from eyes and skin. It isn't related to the citrus fruit.
Is hominy nixtamalized corn?
Yes. Hominy is whole nixtamalized corn kernels, often puffed. It's used in pozole and can be ground into masa.
Is masa harina the same as fresh masa?
Masa harina is nixtamalized corn that's been dried and ground into flour. Mixed with water it makes a dough similar to fresh masa, though fresh masa tends to taste fuller.