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66 / the tasting panel / may 2017 COVER STORY the bottle. "A good start is checking the label to see if it specifies that the tequila is made from 100 percent blue agave." Although only the blue agave plant can be used for tequila, the Mexican government, which regulates the name "tequila," allows up to 49 percent of other sugar derivatives in the fermenta- tion. The best tequilas use 100 percent blue agave. For Carlos, anything that dilutes the unique expression of terroir compromises the ultimate product. As with wine, tequila's flavors and aromas are influenced by the specific geological and climatic conditions the plant experiences. He points out that these conditions are strikingly different between the Jalisco Highlands and the Tequila Valley. El Tesoro's agave, for example, comes from 100 percent estate-owned fields in the Highlands, where the iron content dyes the soils red. Carlos explained to us that "iron is a precursor to sugar formation in the plants, so that's the reason Highlands agave is sweeter than the valley's." Iron also infuses the water source with minerals, lending minerality to the finished tequila. That minerality was displayed exquisitely in both aromas and flavors in all four tequilas we tasted, but particularly in the unoaked El Tesoro Blanco. All these subtleties and finesse can perish quickly with harsh production methods driven by cost efficiency. At La Alteña, quality is the driver, and time the investment. El Tesoro is fashioned with the same level of care demanded by a First Growth Bordeaux. The care begins in the fields where it takes seven or eight long years for the agave to mature before the plants are hand har- vested by skilled workers called jimadors. The jimadors trim the plants' long leaves in the field, leaving a core called the piña, which resembles a pineapple. Then, in the distillery, they use an axe to carefully remove any bitter waxy remains of the leaves. After that, the piña is cooked to convert starch to sugar in an unhurried slow-roasting process that continues for 72 hours. The cook- ing is done in traditional ovens called hornos, cleaned every 10 to 12 hours to remove any bitter, waxy residue. Overall, it's a process that lasts an eternity compared to the commonly used autoclave. Autoclaves whiz through job a bit more roughly in seven or eight hours. By far, the most unique and traditional part of the El Tesoro production is the use of a two-ton volcanic stone, called the tahona. Once pulled by donkeys and now by tractor, the tahona is driven around in circles so that its weight gently squeezes the juice from the pulp of the cooked piña. "It's inefficient," Carlos admits, "but what we lose in volume, we gain in flavor." The tahona leaves lots of juice in the pulp, but both pulp and juice will be fermented together with the help of a few billion wild yeast. Carlos believes wild yeast is another component to complexity, so commercial yeast is nixed while the wild yeast are encouraged to swim in the open-top wooden fermentation vats. El Tesoro Tequila's agave comes from 100 percent estate- owned fields in the Highlands of Jalisco. San Francisco bartender Karri Cormican shakes up a classic Tommy's Margarita, made with El Tesoro Tequila Blanco. PHOTO: HARDY WILSON