At Tommy’s Mexican Restaurant in the Outer Richmond, Julio Bermejo manages an extensive collection of Tequilas alongside a menu that features Yucatecan dishes like panuchos, tamales and poc chuc. Bermejo and his bartenders mix those Tequilas with agave syrup and lime juice to yield hundreds of flavor variations on the iconic Tommy’s Margarita that Bermejo first developed in the early 1990s.

The flavor soul of most food ingredients is split into halves that rarely mix: one that thrives in water and one that lusts after fat. Sugars, acids, salts and other tasty bits tend to avoid fat at all cost and dissolve best in water. Most aromas, including the smelly essential oils found in fruits, nuts, spices, and herbs, are physically incapable of dissolving in water and are most effectively captured in fats and oils.

Alcohol — specifically ethanol, the drinking variety — represents a neutral territory between these two worlds, an edible temple where tastes, smells and colors can congregate in greater diversity than anything else we consume.

The chemical flexibility of alcohol to capture whatever we throw at it means that liquor has a keen memory. Booze chemically records any shortcuts farmers, distillers or bartenders take, which is why bottom-shelf well drinks often rely on blinding doses of sugar and color to hide the sins logged within the liquor. When shepherded by skilled and thoughtful artisans from source to sip, however, alcohol can reflect deliciousness with divine precision.

Bermejo creates his greatest alcoholic fresco, the Tommy’s Margarita, by using pure agave nectar and fresh-squeezed lime juice to highlight, not hide, his high-quality Tequilas. Restrained sweetness and a calibrated sour punch provide an easy-drinking frame through which diners can appreciate the flavors captured by each Tequila in the course of its journey to the bottle.

Tequila

Mexican law stipulates that a spirit can only be labeled Tequila if it uses agave as the primary ingredient. This leads some Tequila brands to blend the minimum required amount of agave (51 percent) with cheaper ingredients like corn syrup or cane sugar. These supplemental ingredients aren’t necessarily sinister, just anonymous; they’ve been stripped down to standardized sugar nubs in order to provide cost-effective fuel for fermentation.

By serving only Tequilas made from 100 percent agave, Bermejo treats his patrons to intoxication as well as a show, a potable chronicling of the life and afterlife of the agave itself.

Agave plants are thorny fortresses built to survive extreme conditions in arid highlands and desert valleys. To help them withstand this harsh habitat, agaves stockpile a specialized carb called inulin. Inulin is a chemical cousin to the starch hoarded by potatoes and corn, and it provides a stable glut of energy that agaves can nibble on over years of slow growth.

There are hundreds of species of agave, but the blue agave is the only species used for Tequila production. Blue agaves amass fat caches of inulin but are unlike other species that guard those riches with tough fibers and harsh-smelling chemical deterrents.

Jimadores, the shepherds of this immobile flock, spend about a decade escorting each blue agave plant to maturity. When ready for harvest, a jimador hacks off the agave’s outer leaves to expose the bulbous central stalk, often called a piña because it resembles a pineapple.

Jimadores in the highlands tend to give their piñas a closer shave than jimadores in the valleys, who leave a few centimeters of green stubble on the agaves’ harvested cores. Shadows of the proteins, fibers and trace fats in that leafy scruff hang around throughout the Tequila-making process to imbue lowland Tequilas with a characteristic grassy earthiness.

Mature agave stalks, which can weigh as much as a linebacker, pack a raw carbohydrate payload large enough to feed hordes of alcohol-producing yeasts. But inulin is an enormous molecule, and yeasts prefer to feast on dainty morsels.

Tequila makers set the table for microbial bacchanal by slow-roasting the harvested piñas in enormous ovens to render tangled knots of inulin into bite-sized bits of fructose. After several days of baking, each piña becomes a quivering mass of sugary syrup infused with nutty, caramelly and occasionally smoky aromas, depending on the roasting style of the facility.

After cutting, crushing and milling the cooked piñas to liberate sweet juice from their fibrous pulp, Tequila producers step back and let the yeasts go to work. Some producers employ refined strains of yeast that are cultured to efficiently churn sugar into ethanol, while others favor the complicated fragrances that arise when the juice is left exposed to whatever local, yeasty misfits happen to land onto the syrup.

Eventually, all yeasts eat themselves out of a job. When the yeasts exhaust their food supply and start to die off from swimming in too much alcohol, the fermented agave mash is passed off to the distiller.

Water requires a ton of heat to boil because water molecules are homebodies that are chemically inclined to stay put. Alcohol, on the other hand, loves to party. When a distiller heats a pot of fermented agave wine, alcohol is first out the door, dancing upwards as curls of boozy vapor. When funneled over a chilled tube of coiled metal, these intoxicating cloudlets condense into tiny, high-proof drops that drip into a separate container.

Tequila is distilled to a maximum 55 percent alcohol level, which leaves plenty of room for flavorful, non-booze constituents. While vodka makers distill their spirits to oblivion — often up to 95 percent before diluting them with water down to market strength in search of nearly featureless purity and smoothness — Tequila distillers exalt in the quirky edges of their liquor. Their approach to distillation is like brewing coffee — meticulous agriculture, attentive fermentation and calibrated roasting profiles culminate in a carefully extracted rainbow of tastes and aromas.

The distillate can be bottled fresh as white or silver Tequila, rested for a couple of months for Tequila reposado or aged for a year or more to yield Tequila añejo. All aged Tequila matures in oak barrels, but that oak can come from anywhere — freshly charred French oak, American bourbon barrels, even decades-old Spanish sherry casks.

Apart from insisting on 100 percent agave-derived product, Bermejo isn’t a purist. He makes margaritas with Tequilas of all ages and provenances, using the beverage as a lens to put the many facets of Tequila terroir on display.

Agave syrup

If you go Tommy’s Mexican Restaurant Lunch, dinner Wednesday-Monday. 5929 Geary Blvd., San Francisco. 415-387-4747 or http://www.tommystequila.com.

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Bermejo holds the sweetener for his margaritas to the same standards as his Tequila; only syrup derived from 100 percent agave is allowed. His favorite agave syrups come from Tequila producers who pack drums of sweet nectar immediately after roasting and milling.

Bermejo prefers agave nectar made from piñas that are roasted at lower-than-average temperatures and pulled from the ovens before aggressive caramelization kicks in. He wants the color of his margaritas to signal the age of the Tequila, and old, over-roasted syrup can make any Tequila seem a little bit añejo.

When a fresh drum of agave nectar arrives at Tommy’s, Bermejo and his bartenders taste and dilute it to create an easily-mixed simple syrup, using variable amounts of water to compensate for the natural ebb and flow of sugar content from seasonal agave harvests.

Lime juice

Acidity modulates our perception of both sweetness and bitterness, making citrus an effective mediator in the binary struggle between bitter ethanol and sweet sugar. Bermejo relies on the sour punch of fresh lime juice to balance his margaritas rather than using a heavily sweetened, citrus-essenced liqueur like triple sec.

Lime juice isn’t just pure citric acid; it’s a diverse mixture of acids, sugars and essential oils. In sauces, soups or nonalcoholic limeades, resinous oils from lime zest give us fleeting whispers of lime aroma. In a margarita, however, lime oils can ricochet around the highly flavor-conductive alcohol like sound on the walls of a high school gymnasium, amplifying the flavor of lime rind to a distracting discord.

For consistent juicing, Tommy’s bartenders use a common elbow press juicer, and Bermejo trains his bartenders to lop off the nubby end of each lime half at its apex. This prevents direct contact between the fragrant zest and the juicing press and holds the flow of lime oil to a mere trickle, perfectly tuned to add subtle harmonies in the background.

Citrus juice has a short shelf life. Immediately after juicing, its aroma begins to oxidize, its color darkens, and its acidity becomes less potent. To protect the flavorful sanctity of his margaritas, Bermejo insists that every single lime at Tommy’s is juiced a la minute, just in time for the show.

Ali Bouzari, Ph.D., is a culinary scientist, co-founder of Pilot R&D and Render, and author of the book “Ingredient: Unveiling the Essential Elements of Food.” Twitter: @alibouzari Instagram: @bouzariali Email: food@sfchronicle.com