Nixtamal is dried corn that has been cooked and soaked in an alkaline solution, typically water mixed with calcium hydroxide (commonly called “cal” or slaked lime). This ancient process, called nixtamalization, softens the kernels, loosens their outer skins, and fundamentally changes the corn’s nutrition, flavor, and texture. The resulting nixtamal can be ground into masa (the dough used for tortillas and tamales) or left whole as hominy for stews like posole.
How Corn Becomes Nixtamal
The process starts by simmering dried corn kernels in water with roughly 1 to 2 grams of calcium hydroxide per 100 grams of corn. The lime raises the water’s pH to around 11, making it strongly alkaline. After a brief boil, the corn steeps in this solution for several hours or overnight. During that time, the alkaline water penetrates the kernels, dissolving the waxy outer hull (called the pericarp) and breaking down the proteins that bind the corn’s starch granules together.
After steeping, the corn is rinsed to wash away the dissolved hulls and excess lime. What remains is nixtamal: plump, fragrant kernels with a slightly slippery surface and a distinctive earthy, almost floral aroma that raw corn doesn’t have. The starch inside the kernels partially gelatinizes during cooking, which is what gives ground nixtamal its ability to form a smooth, pliable dough. Without this step, ground corn crumbles apart instead of holding together.
Why Alkaline Processing Changes the Nutrition
Raw corn contains niacin (vitamin B3), but in a form the human body can’t absorb. The niacin is chemically bound to other molecules, essentially locked away. Alkaline processing at a pH of about 11 breaks those bonds and releases niacin into a bioavailable form. This distinction had enormous consequences historically: populations in Mesoamerica who nixtamalized their corn avoided pellagra, a devastating niacin-deficiency disease marked by diarrhea, dermatitis, dementia, and potentially death. When European and African populations adopted corn as a staple without the alkaline treatment, pellagra became widespread. The connection wasn’t formally identified until 1951, when researchers confirmed that niacin in untreated corn is biologically unavailable.
Beyond niacin, nixtamalization increases the corn’s calcium content (absorbed from the lime water), raises dietary fiber and resistant starch levels, and lowers the glycemic index compared to non-nixtamalized cornmeal. That means nixtamal-based foods produce a slower, more moderate rise in blood sugar than products made from plain ground corn.
Built-In Food Safety
Corn is susceptible to mold contamination during storage, and those molds can produce mycotoxins, particularly aflatoxins, which are potent carcinogens. Nixtamalization significantly reduces mycotoxin levels through two mechanisms: the alkaline solution chemically degrades some toxin molecules, and the steeping and washing steps physically remove others along with the dissolved hull material.
The reduction varies depending on contamination levels and processing conditions, but studies have found that nixtamalization lowers aflatoxin concentrations in corn by roughly 15% to 92%, with most results falling in the 40% to 65% range. That wide spread reflects differences in lime concentration, cooking time, and how thoroughly the corn is washed. It’s not a complete elimination, but it represents a substantial safety improvement, especially in regions where corn may be stored in conditions that favor mold growth.
What Nixtamal Becomes in the Kitchen
Nixtamal is the starting point for a wide range of foods, and what you do with it after the alkaline soak determines the final product.
- Masa for tortillas: Nixtamal is ground on a stone mill (or in a food processor) into a smooth, moist dough. This masa is pressed flat and cooked on a hot griddle to make corn tortillas. The partial starch gelatinization from nixtamalization gives tortillas their flexibility, structural uniformity, and shelf life.
- Masa for tamales: The same ground nixtamal, but typically mixed with fat and whipped to a lighter, coarser texture before being wrapped in corn husks and steamed.
- Hominy (whole nixtamal): The intact kernels, with or without the small flower stalk at the base removed, are simmered for an additional hour or more in soups and stews. Posole, the classic Mexican broth loaded with pork or chicken, is the most well-known use.
- Masa harina: Nixtamal that has been ground into masa, then dehydrated into a shelf-stable flour. This is the product sold in grocery stores for making tortillas at home by simply adding water.
Fresh nixtamal has a flavor and aroma that’s noticeably richer than either raw corn or reconstituted masa harina. The alkaline processing develops complex, slightly mineral notes that are central to the taste of authentic tortillas, and it’s the reason many tortilla makers prefer to start from whole dried corn rather than commercial flour.
The Difference Between Nixtamal and Regular Cornmeal
Standard cornmeal and grits are made by grinding dried corn without any alkaline treatment. The hull may be mechanically removed, but the starch structure and protein matrix remain intact. This means cornmeal won’t form a cohesive dough, lacks the characteristic tortilla flavor, has lower bioavailable niacin, and retains more of any mycotoxins present in the grain. Products labeled “masa” or “masa harina” always indicate nixtamalized corn. If a package just says “cornmeal” or “corn flour,” the alkaline step was skipped.
The distinction matters nutritionally for anyone relying on corn as a primary calorie source. For occasional use, the difference is mainly about flavor and texture. But for billions of people worldwide who eat corn daily, nixtamalization transforms an adequate grain into a significantly more complete food.