Brettanomyces, a Funky Yeast, Makes Flavorful Beers

Written by Daniel Fromson for The New York Times

A CREATURE is lurking here in Chad Yakobson’s warehouse, inside the oak barrels where he ages most of his beers. Its name is Brettanomyces, and it’s a cousin of the domesticated yeasts that humans have brewed with for thousands of years. Often called wild yeast — a reference to its natural habitat (fruit skins) and to its volatile temperament — “Brett,” as it is widely known, can lead to unpredictable fermentations and gushing beer bottles, aromas politely described as funky, and fear. Most brewers work hard to keep it out of their tanks by sterilizing every piece of equipment.

But Mr. Yakobson, 28, who studied winemaking before founding his brewery, Crooked Stave Artisan Beer Project, in 2010, treats Brett like an old friend, pointing out that it was common in beer before the advent of modern sanitation in the late 19th century. He prizes the hints of tropical fruit, earthiness, spiciness and, yes, funkiness that it lends to his beers, which include an herbal India pale ale, Belgian-inspired saisons and sour ales reminiscent of Belgian lambics.

“It’s an entire new category of beers,” often called wild or Brett beers, Mr. Yakobson said one afternoon as he stood among old wine and spirits casks and elephant-size barrels called foudres.

Bitter or mild, light or dark, acidic or barely tart, and frequently barrel-aged, these ales all share winelike nuances that most other craft beers lack. Although they comprise only a sliver of the beer market and challenge many drinkers’ ideas of what beer should taste like, they have nonetheless captured the imaginations of a growing number of brewers and aficionados. They also show off the sense of artisanship and depth of flavor that increasingly define American craft beer.

“There’s so much complexity that’s gained from Brett usage,” said Tomme Arthur, co-owner of Port Brewing and its sister brand the Lost Abbey, in San Marcos, Calif. “We just looked at it as an opportunity, and that’s what you’re seeing with craft brewers these days: they’re not, as we say, being afraid of the big bad Brett.”

Mr. Arthur is one of a handful of brewers in the United States who helped generate interest in wild beers about a decade ago, when they began riffing on the lambic beers and Flemish red and brown ales of Belgium. In these barrel-aged styles, which the majority of American wild beers still resemble, Brettanomyces (pronounced brett-TAN-oh-MY-sees) mingles with lactic acid bacteria, which yields a sourness that brings to mind lemons, sour cherries or balsamic vinegar.

Today, brewers are adding Brett to a much wider array of beer styles, many of which are not sour at all, and more palatable to the average drinker. At Green Flash Brewing in San Diego, the Rayon Vert Belgian-style pale ale combines citrusy American hops with earthy Brettanomyces notes. The beer is similar to Orval, the iconic Belgian Trappist ale.

“What we were shooting for in this beer is, ‘What would Green Flash be if we were a pre-World War II Belgian brewery?’ ” said Mike Hinkley, the chief executive of Green Flash.

Indeed, the popularity of wild beers seems to stem in part from brewers’ enthusiasm for reviving the tastes of the past, in much the same way that cheesemakers study centuries-old aging methods, or farmers grow heirloom vegetables.

“I mean, Americans started making craft beer because they were dissatisfied with the flavors that were available,” said the wild beer pioneer Ron Jeffries, the founder of Jolly Pumpkin Artisan Ales, in Michigan. “Thirty, 40 years later, that hasn’t changed — it’s about the flavors, great flavors, that you can’t get anywhere else.”

Like conventional brewing yeast — which, depending on the strain and fermentation conditions, can produce anything from the banana and clove notes of German hefeweizens to the neutral aroma of Budweiser — Brett can vary widely in its influence on beer. With Brett, the flavors often intensify in the bottle, as the yeast slowly metabolizes complex sugars.

Brian Strumke of Stillwater Artisanal Ales, which is based in Baltimore, says he likes the rounded earthiness and spiciness that wild yeast lends to several of his variations on the Belgian saison style, noting that his Brett beers are the ones he most likes to drink himself. David Logsdon of Logsdon Farmhouse Ales, in Hood River County, Ore., says people who like wine tend to gravitate toward his wild beers, because of their fruitiness and acidity.

The similarities aren’t lost on Vedran Mehinovic, a 31-year-old composer from New Haven. “The sour beers — I’m a big fan,” he said on a recent weeknight as he sat in the restaurant and beer bar Jimmy’s No. 43, in the East Village in Manhattan. Mr. Mehinovic especially admires Interlude, a wild beer from Allagash Brewing, of Maine. “I would say that it is more complex than any wine.”

Many brewers, however, believe that wild beers will never become truly mainstream. “The flavors are just a little too far out there,” said Vinnie Cilurzo of Russian River Brewing in Santa Rosa, Calif., particularly the pronounced earthiness and occasional barnyard aromas. The high costs of making wild beers, which tend to be aged far longer than normal ales and often require dedicated equipment, deter many breweries; there is also the risk that wild yeast will contaminate so-called clean, or conventional, beers.

Still, passionate brewers have managed to educate many customers about the pleasures of wild beers. The niche, Mr. Cilurzo said, is likely to keep growing as long as younger brewers keep taking up the cause.

He pointed out that he recently collaborated on a beer, Brux, with his friend Brian Grossman, son of the Sierra Nevada Brewing founder, Ken Grossman. They brewed it at Sierra Nevada, now America’s second-largest craft brewery.

“His father had worked to keep bacteria and Brett out of the brewery for years,” Mr. Cilurzo said. “Here is his son’s first big project. And his son brings in this yeast — Brettanomyces.”