For some time, the biggest thing in beer was bold hops, and lots of them. Brewers used them to create flavors and aromas as over the top as a Times Square billboard.
Now you’ll need a microscope to find the most important ingredients at breweries like Ebb & Flow Fermentations, a microbial-minded operation in Cape Girardeau, Mo., near the Mississippi River.
DeWayne Schaaf, the owner and a self-professed “yeast nerd,” ferments his I.P.A.s, sour beers and rustic country ales with yeast strains from Scandinavian farms, bottles of Spanish natural wine and Colorado dandelions. “We don’t use any commercial yeast,” said Mr. Schaaf, who hunts strains and swaps them with scientifically minded brewers.
His efforts pay dividends in distinct aromatics, with few hops required. During fermentation, yeast converts sugars into alcohol and creates pungent esters — organic compounds that might evoke peaches, oranges or pineapples.
For some time, it’s been a hopped-up arms race as breweries regularly double or triple the amount of hops to create stronger aromas. With breweries using the same hops, many beers are starting to smell alike. “How creative can you get?” Mr. Schaaf said.
In search of distinct aromas, brewers are embracing yeast and bacteria strains from across the globe. They’re creating beers that let each type of microbe speak its unique language, and drinkers are listening.
Yeast typically doesn’t provide much fragrance in American brewing. With popular light lagers, “the whole point is to not have any yeast presence,” said Dr. Lance Shaner, an owner and a founder of Omega Yeast, headquartered in Chicago.
Omega Yeast opened in 2013 with a mission to supply brewers with distinctive and dependable yeast strains and souring bacteria. Its catalog contains more than 70 cultures, including laboratory-created hybrids like Saisonstein’s Monster, which creates a dry, lightly tart beer with notes of bubble gum.
“People are psyched about the beers that are weirder and funkier, generally due to their yeast strains,” said Jen Watson, the general manager at Berg’n, a beer hall in Crown Heights, Brooklyn. “There’s a shift in the conversation.”
But newcomers sometimes misunderstand the flavors that yeasts can provide. Alvarado Street Brewery, which has locations in Salinas and Monterey, Calif., once called its hazy I.P.A.s “yeast driven,” highlighting its fruit-forward strains. “Too many people were like, ‘Oh, I love it. It’s so yeasty,’ ” said J.C. Hill, a founder and the director of brewing.
In 2018, Alvarado Street opened a spinoff, Yeast of Eden, in Carmel-by-the-Sea, Calif. The brew pub focuses on mixed-fermentation beers made with yeast and bacteria, and California grains and fruit. The “word soup,” Mr. Hill said, “can be a hard sell.”
His staff offers customers a liquid education: an amuse-bouche of dry, sparkling mixed-fermentation beer. “Their eyes light up,” Mr. Hill said, noting that many people then order a full pour.
Yeast labs are also collaborating with breweries, helping them to stake out fresh, flavorful ground. Jeff Mello, the chief executive of Bootleg Biology in Nashville, regularly brainstorms with breweries about beer styles and fermentation techniques.
He might steer brewers toward his company’s strains, including lager yeast he isolated in his former garden in Arlington, Va., or tailor brewery-specific blends of yeast and bacteria. “We can give breweries new cultures on a weekly basis,” Mr. Mello said.
For generations, brewers in western Norway have fermented their farmhouse ales with a family of yeast called kveik. Each brewer’s culture is a living heirloom. “You’re brewing the same beer that your dad brewed and his dad brewed,” said Lars Marius Garshol, the Norwegian author of “Historical Brewing Techniques: The Lost Art of Farmhouse Brewing,” out in April. “It was nothing special.”
He discovered that kveik contradicted fermentation’s commonly understood framework. Most beers are fermented with one strain. Kveik is a “choir of yeast,” potentially dozens, that fast-tracks fermentation. Beer can be drinkable in as few as two or three days, compared with the two weeks required for ale yeast.
More curiously, kveik ferments at up to 100 degrees and produces sweet, fruity aromas. (Hot fermentations usually stress yeast and smell like solvents.)
Several years ago, Mr. Garshol said, he shared kveik samples with U.S. yeast suppliers such as Omega, hoping to “present the brewing world with a new universe of flavors, methods and traditions.” Now, American brewers are increasingly embracing kveik’s unique qualities.
Mr. Schaaf, of Ebb & Flow, makes his beers almost exclusively with varieties of kveik. He ferments them hot, by default and design — the brewery was built without temperature control for fermentation.
As single-celled organisms, yeast will never have the visibility of hops. To encourage drinkers to nose around, the veteran yeast supplier White Labs operates breweries and tasting rooms in San Diego, Calif., and Asheville, N.C. White Labs splits batches of beer in half, fermenting each with a contrasting yeast. “People order beer by yeast strains,” said Chris White, the president.
At White Labs Kitchen & Tap in Asheville, the kitchen uses the company’s liquid yeast to ferment sourdough bread and pizza dough, and kveik is a current favorite. By pint and plate, Mr. White said, “we’re sharing the yeast story with the public.”
