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That Worm at the Bottom of Your Mezcal Isn’t a Total Lie

A team of molecular biologists study the chemical composition of mezcal and tequila.

I spent a weekend in Mexico City and drank too much mezcal. Through the haze, I remembered that mezcal is not tequila, and that, at the bottom of some bottles, you may find a worm. I started to wonder whether the rumors were true. The worm has all sorts of mystical powers, people told me. It's an aphrodisiac; it has hallucinogenic properties; it will make you drunker.

I've learned that people who repeat these things are usually just trying to get someone to eat the worm, and they're lying. But the brilliant marketer who spread the word that mezcal with the worm is different was actually telling a shred of truth, according to science.


Antonio De León Rodríguez, a molecular biologist at the IPICYT (Instituto Potosino de Investigación Científica y Tecnológica) in San Luis Potosí, Mexico, has published a number of scientific papers about the chemical makeup of mezcal.

His pride in the liquor is almost as bright and clear as the drink itself. "It's a local product," he told me in explanation as to why he pursued this research; he once published an article in the local newspaper Pulso titled, "Mezcal from Potosi: a very Mexican drink."

Mezcal is a transparent liquor made from distilled agave, a spiky-looking desert plant. It is produced by extracting the heart of the agave plant, roasting it and mashing it to a pulp, then combining it with water and allowing it to ferment in barrels. Depending on how long it's aged, flavors can range from stingingly bitter (joven) to smoother and smoky (añejo). For the añejo variety, a second fermentation can raise the alcohol percentage up to about 55 percent.

Chemically, mezcal and tequila are both similar and different

While mezcal can be made from any number of agave plants, tequila can only be made from blue agave, which means that tequila is technically a mezcal. But the origins of the two liquors are distinct; mezcal originated in the southern state of Oaxaca, and tequila is from the city of Tequila, in the more northern state of Jalisco.

Chemically, mezcal and tequila are both similar and different, according to De León. "Tequila and mezcals have most of the same components, like ethanol, ethyl acetate, heavy alcohols, etc., but they can have variations in how much they contain," he said. Some of the ingredients in even smaller concentrations can affect the aromas and taste.


After comparing mezcal and tequila in one study and determining the best temperature for mezcal's fermentation in another, he and his colleagues turned to the worm, the gusano.

The worm is added at the end of the production process, when the liquor is bottled. It's called a maguey worm, but it's actually a caterpillar, with red and (less desirable) white varieties added to mezcal. It's also commonly used in Mexican cuisine, served fried in tacos or sometimes raw. If you've been around enough mezcal, you'll start to notice that it's only the low-end bottles that still have the worm floating ominously at the bottom.

The legend of the worm is still debated. It didn't start appearing in commercial bottles until the 1940s or 50s, right around the time American tourists started to get hooked on the stuff. Some stories claim the worm was added to some bottles of mezcal to demonstrate its purity. "But one story is that… if the worm remains intact in the bottle, the percentage of alcohol in the spirit is high enough to preserve the pickled worm," according to the Beverage Testing Institute.;


Cynics may chalk it up to marketing. The company Nacional Vinicola, now known as Gusano Rojo ("red worm") was one of the first to include the worm in its mezcal. Legend has it that an employee of the bottling plant, Jacobo Lozano Páez, came up with the idea. It's easy to see why it was an apt gimmick for tourists—it appears both exotic and traditional, and gives dudes a testing ground for their masculinity.

But the worm doesn't just affect the marketing; it actually changes the drink's chemistry, De León said. "Mezcals with the worm have a greater amount of unsaturated compounds and unsaturated alcohols such as… cis-3-Hexen-1-ol."

Cis-3-Hexen-1-ol doesn't have a sexy name, but it has some pretty sexy effects. To humans it usually smells like fresh-cut grass; for other species, it's a real-life aphrodisiac. "Cis-3-Hexen-1-ol has been recognized as a pheromone involved in mechanisms and behaviors of attraction in diverse animals such as insects and mammals," De León said. So far, there's no evidence it has the same effect on humans.

For De León and his team, the next step in studying mezcal will be to help fight for quality. "We're working on a few new studies to guarantee that these Mexican alcoholic beverages are of high quality the way others have done for beverages like vodka and whisky," he said. One day, no one will be able to con you into buying a bottle of bad tequila for three times what it's worth.

Unraveling mezcal's mysteries with chemistry is all well and good, but for De León, there are some pleasures that just can't be explained. "Mezcal just makes you happy," he said. I can attest to that, too.