What is the name of the process of treating corn with calcium hydroxide to make masa?

The process of treating corn with calcium hydroxide to make masa is nixtamalization. Dried maize is cooked and soaked in an alkaline solution, traditionally limewater made with calcium hydroxide, then washed and hulled before being ground into dough.

This is more than a way to soften corn. The alkali loosens the kernel’s outer hull, changes its starches and proteins, and makes the treated grain easier to grind into cohesive masa. Untreated cornmeal generally cannot form the same pliable dough when mixed with water, which is why nixtamalization is fundamental to traditional tortillas, tamales, pupusas, and other foods.

The technique also improves nutrition. It increases the body’s access to niacin-related nutrients and makes tryptophan more available. That mattered in Mesoamerican diets built around maize, because untreated maize can contribute to niacin deficiency when it dominates the diet. Archaeological evidence places nixtamalization in ancient Mesoamerica; equipment associated with the process on Guatemala’s southern coast dates to roughly 1200–1500 BCE.

Nixtamal is the treated corn itself, while masa is the dough made by grinding it. Milling is a later step, not the name of the alkaline treatment.