Tequila, and its country cousin Mezcal, are made by distilling the fermented juice of agave plants in Mexico. The agave is a spiky-leafed member of the lily family (it is not a cactus) and is related to the century plant. By Mexican law the agave spirit called Tequila can be made only from one particular type of agave, the blue agave (Agave Tequiliana Weber), and can be produced only in specifically designated geographic areas, primarily the state of Jalisco in west-central Mexico.At the distillery the piñas are cut into quarters. For Tequila they are then slowly baked in steam ovens or autoclaves (oversized pressure cookers) until all of the starch has been converted to sugars. For Mezcal they are baked in underground ovens heated with wood charcoal (which gives Mezcal its distinctive smoky taste). They are then crushed (traditionally with a stone wheel drawn around a circular trough by a mule) and shredded to extract the sweet juice, called aguamiel (honey water).
The fermentation stage determines whether the final product will be 100 percent agave or mixed ("mixto"). The highest-quality Tequila is made from fermenting and then distilling only agave juice mixed with some water. Mixto is made by fermenting and then distilling a mix of agave juice and other sugars, usually cane sugar with water. Mixtos made and bottled in Mexico can contain up to 40% alcohol derived from other sugars. Mixtos that have been shipped in bulk to other countries for bottling (primarily the United States) may have the agave content further reduced to 51% by the foreign bottler. By Mexican law all 100% agave or aged Tequila must be bottled in Mexico. If a Tequila is 100 percent agave it will always say so on the bottle label. If it doesn t say 100% it is a mixto, although that term is seldom used on bottle labels.