Is Fermentation Responsible for Most of Tequila's Flavor?

In the hierarchy of tequila appreciation, the conversation usually centers on three specific pillars: the field, the wood, and the equipment.

We discuss the terroir of the agave, wondering if it was pulled from the iron-rich red soil of the Highlands or the volcanic earth of the Valley. We debate the nuances of American oak versus French oak, and the years spent resting in the cellar. We even obsess over mechanical methods of extraction, praising the ancient weight of the stone tahona over the modern roller mill.

But according to Jaime Villalobos Sauza, the master distiller for Dos Ángeles Caídos, Entremanos, Suave, and Cachasol, we are largely ignoring the most critical chapter of the story.

As a fifth-generation member of the Sauza family, he belongs to one of the foundational lineages of the tequila world. For him, the choice of agave and the design of the still are merely the boundaries of the canvas. The actual painting is born during fermentation. Working at Hacienda de Oro in Amatitán, Sauza stewards a biological transformation that is as much about intuition as it is about chemistry.

"When you have a proven, solid foundation, innovation for the sake of innovation is unnecessary," Sauza explains. "My family taught me to let the nature do its magic. My grandpa, my father... they were more about oversight of the process and making sure that the nature did its part."

To understand Sauza's passion, one must understand the basic science of the "must." This is the sweet agave juice created after cooking and crushing the agave hearts. In many types of production, a distiller adds a specific, targeted yeast to this juice to guarantee a fast and predictable outcome. In natural or ambient fermentation, however, no yeast is added by human hands.

Yeast is a microscopic fungus that lives everywhere in the natural world. It exists on the waxy skin of the agave plants, in the grain of wooden fermentation vats, and even floats in the air of the distillery. When the sweet juice is left in open-air vats, these wild yeast colonies find the sugar and begin to eat. As they consume the sugar, they convert it into alcohol and carbon dioxide.

But they also produce congeners - tiny chemical compounds that create flavor. Because wild fermentation involves many different types of yeast rather than just one, the resulting flavor profile is often much more layered than its industrial counterparts.

Despite his role in creating some of the most innovative profiles on the market, Sauza maintains a surprising humility about his craft, choosing to view himself through a culinary lens.

"I’m a 'cook' of tequila," he says. "For me, the cook is the one that has the best recipes and knows how to repeat it... but the chef is the one that is always looking for new things. The recipes for the great tequilas were already done 50, 60, 70, 80 years ago. Why change it if you have a solid foundation? My job is to master the recipe."

However, there is a nuance to this stance. While Sauza respects the tradition of the cook, he recognizes that he must act as a chef when it comes to creating differentiation between brands. This is where he ventures into the territory of creating new profiles by leaning into the nuances of the fermentation stage.

It is a common belief among consumers that the agave plant itself provides the majority of the flavor. While the raw materials are the source, Sauza argues that fermentation is the most important stage because it is the primary site of chemical transformation.

"Fermentation is the most important stage because here is where the 'magic' of the transformation happened," he states. "Without the fermentation, you don’t have tequila, you just have cooked agave juice. Most of the flavors and aromas that you are looking for in the final product are produced by the transformation of the chemical compounds. You are looking for the spirit's soul during this stage."

He describes three potential paths for the personality elements found in the agave: they can disappear, they can stay the same, or they can be transformed. In Sauza's view, the "magic" lies in that third path.

Sauza looks to yeast as his primary seasoning. There are two main paths a distiller can take: targeted yeast or natural fermentation. Using a selected yeast strain allows a distiller to ensure a specific profile dominates the environment, providing speed and reliability. However, Sauza’s passion leans toward natural fermentation, where the environment provides a diverse population of wild yeasts that work together.

"If you go with the same kind of selected yeast, you’re only going to have one kind of notes," he explains. "A diversified profile is naturally better because you don’t have only one microorganism working; you have a lot of them. I like to call it a symphony. It’s like when you go to hear a big orchestra; you have a lot of different instruments, and they all together produce a beautiful sound. That’s what happens in natural fermentation."

For the uninitiated, the idea of ambient yeast can sound like marketing fluff, but Sauza breaks down exactly where these microbes come from at Hacienda de Oro. First, there is the roller mill; even with cleaning, tiny crevices inevitably collect sugars where yeast populations thrive. Second, the fermentation tanks themselves are a source, especially wooden tanks whose porous walls retain yeast and non-harmful bacteria from batch to batch.

Finally, there is a biological vector: the fruit fly. Attracted to the sugar in the facility, these flies carry yeasts from the outside world into the tanks. "The fruit fly goes to a lot of fruits in the outside, then they come inside the distillery and they get into the fermentation tanks and they bring the yeast from the outside. Nature has its own way of contributing to the profile if you let it."

Managing natural fermentation for multiple brands is difficult. Sauza views the process as a balance between human intervention and nature.

"70% of ambient fermentation is something you can control, and 30% is just nature," he says. "The consistency of the equipment and the adherence to recipes provide the 70% that maintains a brand's identity. The remaining 30% is where nature speaks. The seasonality of the year also affects the fermentation because the temperature is changing... even the flies and the fruits that are around the distillery are different during the year. That’s the beauty of it."

To create distinct personalities for his brands, Sauza has experimented with different organisms. His most disruptive move was seen with Cachasol, where he selected an IPA Ale yeast strain. Unlike Lager yeasts, which require low temperatures, Ale yeast thrives at the higher temperatures typical of tequila production.

"Using an Ale yeast for the Cachasol project... gives you a different profile of aromas and flavors," he notes. "It amplifies the tropical and citrus notes of the agave. It creates a profile that stands in contrast to other tequilas produced at the same facility."

For the Entremanos Primavera expression, Sauza moved the fermentation process into 500-liter toasted wine barrels. This is about temperature reactivity rather than aging. Smaller barrels respond faster to ambient temperature changes, which affects the character of the fermentation.

"We use 500-liter wine barrels, toasted ones, to ferment... because of the capacity, the temperature is more reactive," he says. "Furthermore, the toasted wood retains specific bacteria and yeasts that a sterile metal tank would not, adding a unique layer of complexity that you just can't get otherwise."

Producing four distinct brands from Sauza at Hacienda de Oro (NOM 1522), and many others created there by distillery owner and master distiller Iliana Partida requires a masterful layering of variables. Sauza explains that "each one of my babies needs to have their own personality," and he achieves this by tweaking the "dials" of production.

Cachasol uses agaves from Nayarit and the IPA yeast to create a vibrant profile.

Entremanos uses an autoclave cooking process of over 60 hours and explores the limits of barrel fermentation.

Dos Ángeles Caídos focuses on the art of the barrel and the long-term interaction between spirit and wood. Because of these specific choices, the brands do not share a flavor profile despite sharing a roof.

Suave uses certified organic Highlands agave, and rests the tequila for a full 28-day “Lunar Month” ensure peak elegance and harmony.

After five generations, Sauza is far from finished. He reveals that for the past year, he has been preparing a "surprise" expression inspired directly by his family’s deep history.

"If you value organic and traditional products, you're looking for that extra effort... that translates directly into quality, purity, and respect for the land," he concludes. "If you want to understand what you are drinking, look past the label. Look at the bubbles in the tank. Look at the microscopic world of the fermentation room. That is where the soul lives."