Beans

Phaseolus vulgaris was domesticated in Mesoamerica, with the Oaxaca valley among the most probable centers of early cultivation. Squash seeds from Guilá Naquitz, Oaxaca, date to approximately 10,000 years ago, placing the site at the earliest stages of plant domestication in the Americas; the common bean's domestication in the same valley follows in the archaeological sequence. The milpa system — maize, beans, squash grown together — developed across Mesoamerica and remains a living agricultural and culinary practice.

The common bean, Phaseolus vulgaris, is among the oldest domesticated plants in the Americas, with evidence of cultivation reaching back to the Oaxaca valley and possibly earlier across Mesoamerica. It forms the third pillar of the milpa alongside maize and squash — a trinity that is not merely agricultural convenience but a nutritional system of considerable sophistication. The bean fixes atmospheric nitrogen back into the soil, sustaining the maize and squash that shade and shelter it. Eaten together with nixtamalized maize, beans supply lysine and other amino acids that maize cannot provide in adequate quantity on its own, producing a protein balance of genuine value to communities whose diet was built on the milpa. In Mexico today, Phaseolus vulgaris appears across the table in an extraordinary range of forms: whole-cooked in their broth (frijoles de olla), strained and fried in lard or oil until they thicken and blister at the edges (frijoles refritos), pureed into soups, mashed as a filling for tortillas and tamales, dressed cold as a salad, or left whole and served as the quiet companion to nearly every comida corrida. The bean is rarely absent from the Mexican table in some form. Race diversity within Phaseolus vulgaris in Mexico is substantial. The Bajío, Jalisco, Oaxaca, and the highland valleys of Puebla and Guerrero each favor distinct local varieties. Among those most commonly encountered: the small, black frijol negro of the southeast (Veracruz, Oaxaca, Chiapas, Yucatán), which cooks to a dense, earthy broth of deep garnet-black; the speckled or cream-tan peruano and its relatives, mild and buttery; the flor de mayo, mottled pink-and-cream, preferred through the Bajío; the bayo and its variants in central Mexico; and the ayocote, Phaseolus coccineus, a larger, older species with a meaty texture, used particularly in Oaxacan and Pueblan cooking. Ayocote is a separate domesticated species entirely — not a variety of P. vulgaris — with deeper, more complex starch character and a firmer skin that holds through long braises. Frijoles de olla — beans of the pot — is the foundational preparation: dried beans soaked or not according to tradition and time, covered with cold water, cooked slowly with a piece of white onion, often a few epazote sprigs (Dysphania ambrosioides), and in some households nothing else at all. The fat, whether lard or a cut of pork, may or may not be added depending on region and cook. In Oaxacan black-bean cooking, a sprig of the herb hierba santa (Piper auritum) sometimes enters the pot. In Yucatán, ibes — white Lima beans, Phaseolus lunatus — replace P. vulgaris in certain preparations. The broth itself, the aguade frijol, is as important as the beans: savory, slightly viscous, deeply flavored, it is served as a thin soup or drunk from the bowl. For frijoles refritos the cooked beans are ladled with their broth into hot fat — the choice of fat is decisive — and worked with a wooden spoon or bean masher until the desired texture is reached. In Jalisco and Michoacán the refried bean is silky and relatively smooth; in Oaxaca, black beans are often left with more texture and served in their broth alongside the fried version; in the Yucatán, frijoles colados — strained black beans — are passed through a sieve and fried until almost paste-like, then spread thin on tortillas for panuchos. Each regional approach is correct within its own tradition. The salt question is not trivial: adding salt early in the cooking process does not, in practice, consistently toughen skins in well-stored dry beans, but very old or poorly stored beans may behave differently. More significant is the age of the bean itself. Beans dried and stored for more than two years cook unevenly, with skins that separate from the cotyledon and a mealy rather than creamy interior. Buying from suppliers with high turnover is more consequential than any cooking adjustment. Epazote in the pot is not optional in many traditions — it is structural. Its volatile oils shift the flavor of the black bean broth into something more complex and resinous, and in folk understanding across the southeast it reduces flatulence. Whether the chemistry of that claim holds, the flavor case for its inclusion needs no such support.

Phaseolus vulgaris black beans produce an earthy, slightly mineral broth with a faint sweetness and, when cooked with epazote, a resinous, almost medicinal edge that reads as savory depth rather than bitterness. Peruano and bayo varieties are noticeably milder and buttery, with less of the tannic quality that black beans carry in their skins. Ayocote beans have a pronounced chestnut-like starch character. The fat used in refritos is a primary flavor variable: fresh lard from leaf fat produces a clean richness; commercial lard varies; neutral vegetable oil yields a flatter result. The bean broth — aguade frijol — concentrates overnight and its flavor shifts, becoming rounder and deeper the following day.