The 3,500-year-old Mesoamerican process of cooking dried maize in alkaline water (calcium hydroxide / cal) to transform it into nixtamal, which is then ground into masa. This isn't just preparation — it's chemistry that unlocks niacin (preventing pellagra), increases calcium content by up to 750%, reduces mycotoxins, and fundamentally changes the protein and starch structure so the corn can form a pliable dough. Without nixtamalization, corn cannot become tortillas, tamales, or any masa-based food. It is the single most important technique in all of Mexican cooking.
Dried corn kernels are cooked in water with 1-1.5% calcium hydroxide by weight of corn. Cooking time 40-90 minutes depending on corn variety and intended use. After cooking, the corn steeps in the alkaline liquid (nejayote) for 8-18 hours — this is where the real transformation happens. The pericarp (hull) loosens and is washed away. The softened, transformed kernels (nixtamal) are ground on a metate or in a mill to produce masa. Fresh masa has a distinctive earthy, complex corn flavour that masa harina (dehydrated masa flour) cannot replicate. Different corn varieties require different cooking and steeping times.
The water should turn golden-yellow during cooking — that's the pericarp dissolving. Test nixtamal by rubbing a kernel between your fingers: the skin should slip off easily. For tortillas, grind to smooth paste. For tamales, slightly coarser. Fresh masa is best used within hours. If you can source heirloom corn varieties, the flavour difference is extraordinary — each variety produces a distinct-tasting masa.
Too much cal makes masa bitter and yellow-green. Too little cal means the pericarp won't release. Not steeping long enough — the overnight soak is where nutrition and texture transform. Not washing thoroughly — residual nejayote tastes unpleasant. Using masa harina and expecting fresh masa results. Grinding too fine or too coarse for the intended product.