Masa & nixtamalization
Corn is the whole platform of Mexican food, and the platform stands on one process: cooking whole corn in an alkaline solution until the hull slides off and the grain turns to a dough that holds. That process — nixtamalization — is why a tortilla is a tortilla, why it stretches without tears, and why a bag of "corn meal" from the baking aisle never behaves the same way.
Corn is not wheat: there is no gluten
Every other dough on this site — doughs & flatbreads, the gyoza skin, the baguette — leans on gluten, the two wheat proteins that link into a network and trap the water and the gas. That network is the structure; it is why a bread holds a crumb and a wrapper holds a seal.
Corn has none of that. If you grind dry corn into flour and mix it with water, you get a gritty, incoherent paste that crumbles the moment you press it, because there is nothing in the particle to bind it to its neighbour. The starch is locked inside the grain's bran, and the protein (zein) is the wrong protein — it won't form a network. Left alone, corn flour is a meal, not a dough.
Nixtamalization is the step that changes that. It is not a cooking of the finished dough; it is a treatment of the whole grain, and it does three things at once. The alkaline bath loosens the hull so it can be rubbed off with the starch still in the grain, hydrolyses the protein so the zein can link into the starch and the mixture takes on a real, stretchy body, and releases the niacin (vitamin B3) that is otherwise bound and unavailable — the same step that made a corn diet viable long before anyone knew what the vitamin was. The result is a masa: corn, chemically converted into a dough.
The alkaline is the point
The "n" in the alkaline is the process. Traditional nixtamal cooks dried corn in a solution of cal (slaked lime, calcium hydroxide) and water. A pinch of baking soda is the closest home equivalent, and a pre-made masa harina is the shortcut — but the alkaline is the whole trick, and skipping it is why the home "cornflour tortilla" falls apart.
Here is the distinction that matters at the shelf: cornflour (the cornstarch you buy for thickening) is pure starch with the protein and the germ removed — it will thicken a sauce and will absolutely never hold a tortilla. Masa harina (look for it in the Mexican aisle) is nixtamalized corn, ground and dried — the alkaline step already done for you. All you do is add water. That one label is the fastest way into a real tortilla at home, and it is what most of the Mexican section assumes.
Hydration is the variable you control
Masa harina sets aside, the dough has one free parameter: water. Too little and it is stiff, cracks when pressed, and the tortilla crumbles on the plate; too much and it is gummy, clings to the comal, and the tortilla tears at the rim. The right point is a masa that holds a ball, is soft, and leaves only a faint impression when you press it — and the only way to find that point with your own hands is to feel it, which is why the tortilla method walks you through the water, a little at a time, rather than giving a fixed measure.
Why the tortilla puffs
When a pressed tortilla hits a hot comal, the moisture in the masa is what cooks it. The surface sets, the interior stays damp, and the steam that builds underneath the set skin lifts the disc into a blister — the puff you see is the tortilla cooking through by steam, the same steam logic as a steamed dish, run in a pan. A good tortilla puffs at one edge; a dry, over-pressured one lies flat and dense. So the heat is high and brief (pan heat at its most direct): enough to set the skin and drive the steam, not so long that the tortilla dries out and turns to a cracker.
Common failures
- The tortilla falls apart when it hits the plate. The masa is under-hydrated and under-kneaded: it will hold in the pan and fall the instant the steam escapes. More water, a few minutes of more kneading, and the dough stays together off the heat.
- It tears at the rim as you press it. The dough is too wet or was pressed while it was still cold and slack. Rest the balls, let them warm a few minutes so the starch relaxes, and press a little at a time. A torn rim is the classic "too much water" mark.
- It sticks to the comal and smears. The disc is too wet, or the comal is not hot enough to set the surface before the moisture soaks in. Higher heat and a drier, thinner press — the surface should set in the first few seconds, not slowly bond.
- It is dense, chewy, and never puffed. Pressed or cooked too slowly, it dries out before the steam does its work. A thicker press and a hotter, briefer cook — you want the puff, which is the sign the moisture cooked the disc through instead of boiling off.
In practice
Tortillas is this article in a kitchen: the nixtamalized harina, the hydration to the right hand feel, the press, and the comal puff, all in one method. Chilaquiles is the same masa at the other end of its life — the tortilla dried, broken, and fried, carrying the salsa and the fry as its own structure. And the whole Mexican section is what a food tradition looks like once one grain has been chemically turned into a dough.