By Harold McGee
These spirits are distilled from the carbohydrate-rich heart of certain Mexican species of the agave, a succulent plant in the Amaryllis family that resembles a cactus. Tequila is made mainly by large distilleries in the central state of Jalisco from the blue agave, Agave tequilana, while the more rustic mezcal is made by small producers in more southerly Oaxaca from the maguey, Agave angustifolia.
The agave stores its energy in the sugar fructose and the long fructose chains called inulin. Because humans lack an enzyme for digesting inulin, people have learned to cook inulin-rich foods for a long time at a low temperature, a treatment that breaks the chains into their component sugars, and also develops an intense and characteristic browned flavor. Tequila makers steam the inulin-rich agave hearts, which may weight 20–100 lb/9–45 kg, while mezcal producers roast them in large charcoal-fired pit ovens and generate smoky aromas that carry over into the spirits. The cooked, sweet hearts are then mashed with water and fermented, and the resulting alcoholic liquid distilled. Tequila distillation is industrial; mezcal is double-distilled, first in small clay pots, then in a larger metal pot still. Most tequila and mezcal is bottled without aging.