Flour tortillas should be called wheat flour tortillas, because there are many other kinds of flour made from a wide variety of grains, including barley, rye, and rice. But you’ll rarely find flour tortillas south of the border. In Mexico tortillas are made from corn. Flour tortillas are a Tex-Mex invention.
The word flour evolved from flower, as used metaphorically to mean the best part of something, such as the flower of a plant or, in culinary use, the best part of a cereal grain.
The supposedly inferior parts, the chaff and bran of the wheat berry and the hull of the corn kernel, have presumably been disposed of. To complicate matters, however, the literal translation of the Spanish masa harina is “flour dough,” with no specification of the kind of flour. On corn tortillas you may also see the more explicit harina de maiz , which distinguishes corn flour from harina de trigo, or wheat flour.
Spanish class dismissed.
The cellulose hulls of corn kernels can be loosened and the germs released by being soaked in water containing an alkali. Acids can be powerful chemicals, but so can alkalis. One exceedingly strong alkali is sodium hydroxide (NaOH), also known as caustic soda or lye. It’s so powerful that we use it to unclog drains, it actually dissolves hair and grease. (It turns the grease into soap, but that’s in Chemistry 102.)
In Mexico, the corn kernels are treated with lime, which is much milder than lye but still strong enough to open the cellulose husks of the corn kernels and uncover the starchy endosperm. Lime has been used for this purpose for thousands of years in Mexico and Central America. The husked kernels are then washed, dried, and ground or pounded into masa (dough).
Small balls of the dough are flattened into very thin, almost perfect disks by the astoundingly dexterous hands of Mexican women, then baked on a hot griddle for 30 to 60 seconds on each side, and distributed still warm and fresh to lucky local Mexicans, who have never had to deal with the factory-produced, machine rolled and stamped out, imitations that we gringos must often settle for.
The main problem with these commercial pretenders is that a fresh corn tortilla should contain about 40 percent moisture, which is almost impossible to maintain during the packaging, freezing, and shipping of the mechanized version.