Nixtamal is made from dried corn that’s soaked in a mixture of water and a mineral called calcium hydroxide. The mineral, which can be white and powdery or rock-shaped depending on where you buy it, adds important nutrients to the corn and better enables our body to digest it. Upon contact with the kernel, the calcium hydroxide pulls at the kernels’ hard outer skin, which eventually sloughs off and makes the corn smoother and easier to grind.
Because of the fluctuating price of corn — and the unpredictable nature of a Mexico City mill, which may or may not have the nixtamal ready by the time customers want or need it — many tortillerías in the capital now use packaged nixtamalized corn flour, like Maseca or Minsa. When I lived in DF, I’d always ask before approaching a new tortillería: “Es de maiz maiz, o Maseca?” If they replied “Cien por ciento maíz”, I’d buy there.
A lot of people are increasingly worried about processed nixtamal flour completely supplanting real corn tortillas someday. To be honest, I’m not entirely sure where I stand, considering that Maseca and Minsa both provide cheap, quick alternatives (and nutrients) to families that may not have time to make their own tortillas daily. I prefer the taste of real corn tortillas, so I seek them out. Most mills in Mexico City still use thick discs made of volcanic rock to grind the corn, so that adds an extra layer of flavor.
The last time I was in Mexico City, I passed by the mill and caught a quick video of the grinder in action. A trickle of water from the faucet makes the dough come together into a solid mass. The bicycle wheel in the bottom-left corner of the frame shows how the workers distribute the masa to fondas and taquerías throughout the neighborhood.