Ross Koenigs knew that scent from somewhere. New Belgium’s research and development brewer was testing a novel strain of Lactobacillus, the souring bacteria that morph milk into yogurt. In fact, this culture came from Noosa, a high-fat, highly flavorful yogurt brand.
Koenigs sniffed his experimental beer again, and his mind skipped back to childhood: SweeTarts candy, at once fruity, acidic, and exotic. “Many lactic acid bacteria produce a clean lactic profile,” Koenigs says. “This one just felt a bit fruitier to us. It was something that we felt was quite unique.”
That Lactobacillus culture led New Belgium Brewing, based in Fort Collins, Colorado, to concoct Broosa Berry Tart, a yogurt-inspired milk stout infused with blueberries, blackberries, and raspberries. Milk sugar builds a bridge to the dairy world, but Broosa is not boozy Go-Gurt. The hybrid drinks jammy and acidic, a roasty surprise made possible by microbes. Says Koenigs, “It hits the flavor characteristics of a stout, but it’s light, crisp, and refreshing.”
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Broosa is part of a growing trend toward beers defined, and differentiated, by offbeat yeast strains and bacteria. It’s tough for brewers to stand apart in today’s bustling beer scene, even if they add day-old doughnuts to a brew kettle. Quirky microorganisms, however, can help brewers carve out a flavorful niche without having to resort to gimmickry or a hop avalanche.
Paul Schneider, the head of brewing operations at Pittsburgh’s Cinderlands Beer Co., has lately been taken with Norway’s kveik (the word is pronounced “kwike” and translates into “yeast” in a Norwegian dialect). Traditionally, kveik fuels the Scandinavian country’s farmhouse ales, as the yeast works well at temperatures north of 80°F, often tossing off a citrusy, tropical aroma and taste.
“Those are flavors that you typically get out of hops,” Schneider says of the strain’s notes of orange, tangerine, papaya, and pineapple. “If we use the kveik and combine it with hops, it gives us a whole new world and platform to build fruit flavors.”
Schneider uses kveik in Cinderlands’ tart grisette, a rustic, low-alcohol style of beer once favored by Belgian miners. “It gives a little bit of residual sweetness to support the fruit flavors that come out of the fermentation and hops,” he says. “It really makes this taste fat and sticky and juicy and ripe. That’s not something I’d get from a typical saison strain.”
Few brewing fungi are more atypical than YH72, which was isolated by Wild Pitch Yeast of Bloomington, Indiana—a company that supplies breweries with novel yeast strains. The offbeat yeast generates lactic acid in beer, no bacteria required. Cleveland’s Saucy Brew Works, which got first crack at using the yeast in a commercial product, brewed a blonde ale dubbed the Drifter. “You’ll notice it’s a sour beer for sure, but it’s much more rounded and mellower,” says Eric Anderson, Saucy’s director of brewing operations. “It’s not sharp.”
YH72 is treated normally—no crazy sanitation protocols needed. “It behaves sort of like regular yeast,” Anderson says, “but it’s interesting that fermentation doesn’t start until after the acid is produced.” YH72 might take two or three days extra to finish fermentation compared with a standard Saucy beer, but it’s like equating apples and aliens. Says Anderson, “They’re a different species altogether.”
That puts Saucy in a linguistic pickle. What do you call these beers? “Technically, it’s a new style of beer that we’re calling a yeast-only sour,” Anderson says. “It’s so novel that we actually had to figure out a way to sell the beer.”
Ballast Point’s best-selling Sculpin IPA has spawned numerous offshoots, including versions infused with grapefruit and habanero peppers. The adjuncts jive because they play off the IPA’s stingingly bitter, tropical hop profile. To create the latest variant, the San Diego brewery looked to its research and development arm.
The R&D team mucks about with new recipes, grains, hops, fruits, and yeast strains, such as Bruxellensis Trois, originally used to ferment an experimental IPA. “We all looked at each other like, This is amazing. We need more of this in all of our lives,” says Lauren Zeidler, Ballast Point’s director of quality.
Trois delivered huge gusts of mango and pineapple, the aromatic compounds a killer complement to Sculpin’s signature scent. Earlier this year, Ballast Point made Trois the star of the lightly hazy Aloha Sculpin, which tastes like a Hawaiian vacation. Aloha scrambles the standard IPA script. Usually, brewers select yeast that produces a pretty neutral flavor profile, creating a stage for hops to generate the applause.
“You almost don’t want to add too many hops, because you don’t want to mute what the yeast is doing,” Zeidler says of the expressive strain.
Ballast Point was the first brewery to release a Trois beer on a national scale. That’s because “this strain is definitely very finicky,” Zeidler says, noting the lengthy fermentation. “It definitely acts wild and has a mind of its own.”
Using new yeasts and bacteria presents no shortage of challenges, and not just on the brewing side. For consumers, “there’s a big learning curve,” says Cinderlands’ Schneider, who takes pains to educate customers about his beers’ distinguishing characteristics. “If that’s what it takes to get people to drink this, I’m happy to take it on,” he adds, noting that he plans to expand his grisette series by rotating kveik yeasts and hops.
“The level of knowledge for the average beer consumer isn’t there yet, but we’re going to do our best to teach them,” Anderson says of Saucy’s yeast-only sours. “It’s really up to us to engage consumers and tell them what the beer is … They’re ordering it and enjoying it, not knowing it’s a very unique and special beer.”
Saucy is committed to using its offbeat yeast, though, deploying a second acid-producing strain in a malt-rich amber ale. Anderson sees this as part of a broader push to redefine beer and steer it to new frontiers. “The yeast map,” he says, “has been relatively unchanged for the last 30 years of craft brewing.”
Brewers favor tested fermentation practices because they consistently work, time and again. Using weird bugs may set a brewer apart, but there’s no certainty that, you know, the beer will taste good—perhaps the most important metric.
“Brewers are a little less likely to take a flier on something that’s just completely unknown,” says New Belgium’s Koenigs. “The beer still needs to turn out.”
Smaller breweries might lack the resources for rigorous research, so it’s partly up to larger breweries to help foment change. “It’s nice for organizations like us that we have more time and bandwidth to play around with some of these more esoteric species,” Koenigs says, adding that a yogurt-culture beer could one day see wider distribution.
For the longest time, yeast and bacteria have worked in the shadows, their roles largely unknown. “I think there’s still a lot of mystery around yeast,” Zeidler says, “and what yeast actually does to make a beer what it is.”
By highlighting yeast and not just another hop, breweries deliver consumers an educational experience and new flavor, a win-win for brains and taste buds alike. Who knows—the market might not be that far away from a day when consumers base their buying decisions on bespoke yeast strains and bacteria.
Cinderlands’ Schneider is confident about that future. “The table has been set for everybody to sit down for that meal, and it’ll be here before you know it,” he says. “Kveik yeast can definitely be the star of the show.”
Joshua M. Bernstein is a beer, spirits, food, and travel journalist, as well as an occasional tour guide, event producer, and industry consultant. He writes for the New York Times, Men’s Journal, New York magazine, Wine Enthusiast, and Imbibe, where he’s a contributing editor in charge of beer coverage. Bernstein is also the author of four books: Brewed Awakening, The Complete Beer Course, Complete IPA, and the just-released Homebrew World. He lives in Brooklyn with his wife and daughter. On the weekends, he can usually be found posting at a local brewery taproom or eating his weight in dumplings.