Agave to tequila

Tequila can only be made from one plant: Agave tequilana Weber, blue variety. It is a succulent, not a cactus, and most plants take six years or more to mature.

It also has to come from one place. Tequila is protected by a denomination of origin that covers the state of Jalisco and parts of Guanajuato, Michoacán, Nayarit and Tamaulipas. Agave spirits made elsewhere, or from other agaves, go by other names, mezcal among them.

When a plant is ready, a jimador cuts away the long spiky leaves with a coa, a flat, round-bladed tool on a long handle. What is left is the heart, the piña, which looks a bit like a giant pineapple.

Raw agave is not sweet. Its sugar is stored as inulin, long chains that yeast cannot eat. Heat breaks them down into sugars that will ferment.

How the piñas get cooked is one of the biggest differences between bottles.

• Horno. A traditional brick or stone oven. Steam cooks the piñas slowly, often a day or two or more. Tends toward deep, cooked-agave sweetness.
• Autoclave. A big steel pressure cooker. Faster, and many well-made tequilas use one.
• Diffuser. Pulls the sugars out of shredded, mostly raw agave with water, then cooks the juice. Very efficient. Critics say it strips out character.

After cooking, the fibers are crushed to release the juice. Some distilleries still use a tahona, a huge volcanic stone wheel rolled around a pit. Most now use mechanical roller mills.

100% agave. Look for these words. If they are not on the label, it is a mixto, which only needs 51% of its sugar from agave. The rest can come from other sugars.

The NOM number. Every bottle carries a NOM followed by a four-digit number. That number identifies the distillery that made it. Many brands share a distillery, so two different labels with the same NOM came out of the same place.

Tequila rules also allow small amounts of certain additives, like caramel color or sweeteners, without listing them. Some producers make a point of using none. If that matters to you, ask us which ones.

Good tequila is for sipping, not shooting. Try it neat, at room temperature, in a narrow glass. Skip the salt and lime the first time.

A blanco shows the agave straight: cooked agave, black pepper, citrus, fresh herbs. A reposado keeps that but adds a little vanilla and rounds the edges. An añejo leans darker, toward caramel and oak, closer to whiskey. Tasting all three from one distillery is the fastest way to learn what the barrel adds and what the agave brings on its own.