Fermenting the Wild

Arizona brewers and winemakers are exploring the world of wild yeasts and natural ferments.

July 11, 2016

BuzzIssue 19: July/August 2016

Like many pioneering producers in Arizona, James Callahan’s education in winemaking was more experiential than academic. In 2012, Callahan returned to Arizona from Northern California to manage his first high-desert grape harvest as winemaker for the newly formed Aridus Wine Company. Having been promoted directly from cellar master to winemaker, Callahan had to fill in the blanks in real time.

Many winemakers cold soak their grapes, a method in which fermentation is purposely stalled while freshly crushed grapes (called “must”) extract color and flavor from their skins before alcohol is present. In order to accomplish this, the native yeasts living on the grape skins must either be killed by the addition of sulphur dioxide or cooled until they became dormant. This time, though, the grapes were arriving too hot from the vineyard; Callahan couldn’t cool them down fast enough to prevent the natural yeasts from beginning fermentation. “At that point I had to make a decision,” he says. “I could have inoculated with a ton of commercial yeast and just beat down the native fermentation or let it go.” He compromised, allowing the strongest batches to continue fermenting “the way Mother Nature intended,” and inoculating the others with a commercial yeast strain.

It was this decision that led to some of Arizona’s first naturally fermented wines—wines that are fermented by native, ambient microflora rather than commercially selected yeast strains.

Brewers at Arizona Wilderness Brewing collect wild yeast from around the state for their naturally fermented brews. Spruce tips provide flavor as well as wild yeast.

Brewers at Arizona Wilderness Brewing collect wild yeast from around the state for their naturally fermented brews. Spruce tips provide flavor as well as wild yeast.

Yeasts are single-celled microorganisms that do the good work of fermentation, the process by which sugars and carbohydrates are converted to alcohol and carbon dioxide. Yeast cultures create drinks that are sparkling and boozy; they raise our bread and sour our pickles. These cultures are naturally present in the wild, typically close to the sugars they seek, such as on the skins of grapes or the fruit of cacti, and need only access to this sugar to begin fermentation—a cluster of grapes that fall from the vine and burst, mixing the sugary juice and native microflora, can spontaneously ferment into a primordial wine.

The history of modern fermentation, then, is the history of the human endeavor to tidy up this process and make the result cleaner, more consistent, and able to be reproduced on a mass scale. The major breakthrough in this evolution was the identification, selection, and cultivation of specific yeast strains that could then be deployed for different results. Rather than waiting for wild cultures of unpredictable yeast and bacteria, modern beer and wine makers could now create sterile conditions in which selected yeast populations would be introduced to ferment their wine and beer which in turn could be returned to a sterile, stable state through pasteurization.


Winegrower Sam Pillsbury (above) works closely with Rune Wines, which uses Pillsbury’s grapes to make naturally fermented wine.

Callahan was happy with the wines he made with commercial yeast strains—they were consistent, focused, and met expectations. The wines that he had allowed to ferment naturally, however, varied widely—some were exceptional, while others were too funky and had to be discarded. Although winemakers can’t afford to discard wine regardless of how exceptional the good ones turn out to be, the experience of spontaneous fermentation made an impact on Callahan and solidified his commitment to making wines with less intervention.

Just two harvests later, Callahan used exclusively native yeasts to ferment Arizona grenache and viognier grapes for his new company Rune Wines. For Callahan, native yeasts have become intimately tied to his idea of high-desert terroir, the French term for a wine’s ability to communicate a sense of time and place. This winemaking is truly “attached to the vineyard,” he says, because it relies on the land not only for fruit but for the agents of fermentation as well. “Everybody talks about a hands-off approach but no one teaches you that,” he says. “Experience is the only real guide.”

In parts of the world with long traditions of brewing and winemaking, many producers still use native microflora to ferment their beer wort or wine must (or agave pulp, honey, etc.), having nurtured a symbiotic relationship with local yeast cultures over centuries. This is much less common in parts of the world where the beer and especially wine industries have grown up with the use of selected yeasts, which support a more consistent and therefore scalable production model.

To the large-scale, commercial brewer, the types of yeast and bacteria that proliferate in the wild can impart a sour or lactic flavor to beer—lactobacillus, brettanomyces, pediococcus—are anathema, like “napalm,” says Patrick Ware of Arizona Wilderness Brewing, remembering his time brewing for a larger-scale producer. “They thought it would ‘infect’ and take over the whole brewery.” This taboo is only now being challenged by a host of progressive Arizona breweries including Wilderness Brewing in Gilbert, Wanderlust Brewing in Flagstaff, and in Tucson, Dragoon Brewing, Flux Brewing, and Iron John’s Brewing—to name a only a few.

A naturally fermented ale involves “taking everything that has been taught to home brewers and production-oriented craft brewers and doing it backwards,” says Ware. Spontaneously fermented beers lend themselves to barrel aging—to nonsterile, semiaerobic conditions in which they can grow and mature while interacting with the surrounding environment. Unlike most beers, which are typically pasteurized and remain in sterile vacuums after fermentation, traditional sour ales mature very slowly and require a range of nutrients to keep the diverse population of microflora alive.

Natural fermentations represent patience in the face of the unknown and a certain faith that things will work themselves out.

“You want unfermentables and residual sugars that will feed into long-term aging and help them express themselves over time,” says Ware. “Locally we have our Sonoran White wheat, a rustic grain we can incorporate into beers and especially sours, which gives the long-chain dextrins, the proteins and amino acids, that we’re looking for these yeasts and bacteria to break down over time.”

As these microflora pass what Callahan calls “the relay baton” between “many different organisms across the spectrum of fermentation,” each bacteria and yeast lend a particular note to the end product, creating a depth of flavor and nuance that a commercial yeast culture cannot replicate.

To return to the use of natural yeasts is a step backward in many ways, and, to these small-scale producers, it is a welcome one. Natural yeast ferments require patience, adaptability, and a certain embrace of unpredictability, all of which make them more at home in a microbrewery, where their maturation can be closely monitored and the rigors of export don’t apply. The small scale and localism inherent in the production of these beers allows for an educational dialogue with the public, helping inform their experience of what is, to many, a new encounter with a very old style of beer.

Chris Ray, a brewer at Wilderness, taste-tests a brew in the barrel room, where wild-collected yeast strands ferment wort into beer.

Chris Ray, a brewer at Wilderness, taste-tests a brew in the barrel room, where wild-collected yeast strands ferment wort into beer.

In order to capture native strains of yeast and bacteria, Wilderness has developed what they call a “mobile cool ship,” a truck bearing two oak barrels under a large steel pan. The first “cool ships” were found in Belgium’s farmhouses where brewers would pump wort into open-air lofts rich in microflora. Mimicking this process, Ware and Buford drive their unfermented wort to wilderness areas, pump the wort from the barrel to fermentation tray, and let the microflora specific to that area feast, taking up residence in the sweet wort as they begin to ferment the sugars into alcohol. These beers cannot be reproduced, each having a character determined by seasonal variables and, Buford notes, “the differences in terms of thermodynamics and topography” of a specific place at a specific time.

Once the beer is back in the brewery, the long process of maturation in oak barrels begins. There is no recipe, only observation as the beer morphs under the influence of different strains of wild yeast activating or going dormant. “Whereas in most beer-making the process is absolutely everything,” says White at Dragoon. “For sours it’s only the beginning.” The human element of tasting, rendered obsolete in industrial-scale brewing, becomes indispensable when making these slow aging beers. “All the chemical analysis in the world doesn’t matter if the taste isn’t right,” says White.

The idea of a beer naturally fermenting toward an unknown state is especially rich for Buford. “There were always rules where I came from. You had to preplan before you did anything, but out here, the Wild West, the way Arizona is, you don’t, you never know what’s next, and so you don’t know what the limitations are.”

What, then, is at stake here? More than a type of yeast, brewers are talking about an entire mindset. If commercial yeast fermentations represent the controlled, the predictable, the scalable, then natural fermentations seem to represent patience in the face of the unknown and a certain faith that things will work themselves out.

Why, then, isn’t everybody making this magical elixir the way Mother Nature intended? Mostly because, as all the brewers and winemakers noted, unpredictable doesn’t always mean unpredictably good. When the Dragoon team tasted through their 10 barrels of sour ale, the only blend everybody could agree upon was of two barrels, meaning the other eight barrels, which they had been maturing for over two years, had to be discarded.

The same is true with wine. Callahan notes that naturally fermented wines require constant monitoring in the cellar and leave no room for error—the bacteria on a rotten grape cluster, if let into the winery, could throw off the whole ferment.

hris Rodgers, a brewer at Wilderness, in the brewery’s fermentation room.

Chris Rodgers, a brewer at Wilderness, in the brewery’s fermentation room.

And while many agree that wine and beer can benefit from the subtle nuances of wild ferments, it can just as easily be overcome by them. Nathan Friedman of Wanderlust called these issues the yin and yang of fermentation, and advocated a scientifically informed artistry in beer-making, meeting the natural process halfway. For Friedman, this meant first capturing local yeasts by making a cider and allowing it to ferment naturally in open-air containers. Once the cider finished fermenting, Friedman was able to isolate and analyze the cultures within, cultivating the specific strains that he felt worked best in his beer.

If commercial yeast strains were selected and bred for strength and consistency, wild yeasts represent a subtler and more delicate road to fermentation—one that involves more risk but potentially more reward as well. Naturally fermented wine and beer take us back to a time when fermentation was the cultivation of a living thing, a culture that could be assisted but not controlled. They remind us that when we learned to control the fermentation process via selected yeast strains, we didn’t just lose a style of beer but also an experience of encountering the unknown and working alongside it.

When brewers and winemakers work with native yeasts, they are taking a risk for the sake of nuance, terroir, and individuality. It makes sense then that the flavors of these ferments tend to be on the savory side and can require more than initial impressions to appreciate. Producers use a host of terms to describe these products—reductive, barnyard, lactic, sour, alive, volatile, vinegary, subtle—all of which gesture to an encounter on the other side of sweet, fruity, or fresh.

The successful sour ales and naturally fermented wines will never be exactly recreated because they cannot be, and the expectation of the consumer must therefore be to have no expectations. So is it worth the trouble to create an essentially one-off product? Yes, say producers, because something deeper happens that many feel is worth fighting for—a recalibration of how we modern consumers approach the things we consume. When we allow the spontaneous and the unpredictable to take precedence over the controlled and consistent, something substantial happens in which we begin to approach things with, perhaps, a sense of adventure rather than expectation. We begin to acquire tastes rather than enjoy what we already know. In other words, these natural fermentations begin to teach us how to approach things “on their own terms,” as Buford says. In a way, it is simply a humble celebration of the unknown.

Luke Anable is a Tucson transplant, natural wine protagonist, and beverage consultant for independent restaurants.

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