Native Cultures: Experiments in Spontaneous Fermentation
A pair of fermentation tanks dominate the unfinished space inside the Mystic Brewery. The tanks jump out at visitors because the blocky, custom-made, flat-bottomed vessels look more like the cyborg Daleks from Doctor Who than the stainless conical fermentors that fill most American breweries. But while the distinct tanks loom over Mystic, a startup operation located in Chelsea, Mass., an industrial suburb of Boston, the real experimentation is happening inside dozens and dozens of Petri dishes and Mason jars.
Mystic’s founder, Bryan Greenhagen, wants to do with yeast what West Coast brewers have done with hops. With the help of his wife, Emily—both are MIT grads—he wants to establish a New England brewing identity that’s intertwined with native yeasts and other microorganisms. But first, he has to find some native yeast. That’s where all the jars and dishes come into play. Greenhagen is sorting through hundreds of wild yeast strains, looking for a few that will play nicely with malt and hops.
“We have to invent a beer to match the yeast,” Greenhagen says. “That synergy worked in the past. You’d change ingredients based on what yeast was naturally available.” It’s a practice now commonly associated with Belgian farmhouse and Lambic brewers, but one that Greenhagen insists is “not necessarily Belgian, just pre-industrial.”
Greenhagen isn’t alone in looking to push beyond conventional fermentation processes. Craft brewers live to push boundaries. It’s in their blood. Experimentation is what makes craft beer different than the formulaic yellow lagers derived from a single malt, a single hop variety and a single yeast strain. And while innovation in the form of new hop varieties, unconventional fermentables and new barrel-aging treatments are driving beer-making forward, when it comes to fermentation, the future is decidedly backward-looking.
Without yeast, there is no beer. Yeast does the yeoman’s work of turning sugars into alcohol. Its esters also give many Belgian, British and German ales their defining characteristics. Even so, the catalog of actively employed brewing yeasts is limited, relative to the countless permutations of naturally occurring yeast strains.
The bulk of the brewing yeast used by commercial brewhouses and homebrewers is derived from a few strains of European yeast. Strains were selected for their alcohol tolerance, contribution to head retention, flocculation, behavior at controlled temperatures and ability to produce pleasant esters. The narrowing of the yeast universe advanced along with the industrialization of brewing, as brewers needed predictable, replicable results.
Of course, brewing existed before industrialization, and it thrived on naturally occurring yeasts and other microorganisms. Farmers brewed with ingredients surrounding their farm-brewery, including whatever yeast floated around in the air. And brewers of Belgian Lambics continue to rely on wild yeast strains that spontaneously ferment their beers, rather than pitching a carefully selected strain into a barrel of wort.
Rob Tod recalls visiting some of these spontaneous Belgian breweries with a group of American brewers, and wondering whether their techniques could be imported to the US. As the founder of Allagash Brewing Co. bounced around Brussels and the Senne valley with Dogfish Head’s Sam Calagione, Russian River’s Vinnie Cilurzo, The Lost Abbey’s Tomme Arthur, and Avery Brewing’s Adam Avery, Tod was repeatedly told that the beers he was drinking could only be brewed in a specific corner of Belgium. Just one brewer, Cantillon’s Jean Van Roy, thought the Americans might be able to pull off a spontaneous Lambic-style beer.
Tod ran with Van Roy’s encouragement. Allagash built a coolship—a wide, shallow tank—in a room connected to their brewery in Portland, Maine. Tod and Allagash brewmaster Jason Perkins cooked up a beer along the lines of a traditional Lambic (aged hops, plenty of raw wheat and a long boil), pumped the hot liquid into the coolship, and left it there overnight, with the windows open. They racked the wort into French oak barrels the next day. Sure enough, natural airborne microbes went to work. The end result tastes similar to the Lambics that Belgian brewers have been making for hundreds of years.
“We didn’t know whether we could sell it, or what it would taste like,” Tod says. “We were just curious about whether it would work.”
Allagash has been brewing and aging spontaneously fermented ales for over three years now, and the brewery will be releasing a line of spontaneous beers, due on shelves by mid-August. The line includes tart, effervescent beers aged with raspberries and cherries, as well as a blend of young and old spontaneously fermented beer, along the lines of a Belgian Gueuze.
Russian River’s Vinnie Cilurzo also launched a spontaneous fermentation project after traveling to Belgium with Tod. Russian River’s spontaneous beers are sharper and more acidic than Belgian Lambics, a product of both the natural microbes floating around Sonoma County in California, and the wild bugs that thrive in Russian River’s sour barrel room. Cilurzo helped popularize the use of wild bacteria and a wild yeast, Brettanomyces, in American brewing; for him, letting his wort ferment on its own was a natural progression in the funky fermentation he’d already been employing.
Beatification, Russian River’s spontaneous beer, draws from the same Lambic-style recipe that Allagash and Cantillon employ. Cilurzo brews his spontaneous beers over three days: He’ll do a sour mash on a Friday night, run the mash off into the kettle on a Saturday morning, do a long boil with aged hops, and then rack the wort back into the mash tun to cool overnight.
Cilurzo isn’t exactly sure what’s driving fermentation for Beatification, since it’s drawing microbes from the air, the mash tun, the sour barrel room and the barrels he ferments in. But it’s safe to say the beer is fermented with wild Saccharomyces, Brettanomyces, Lactobacillus and Pediococcus; Cilurzo believes it probably contains some other microorganisms as well, but he’s not too concerned with the beer’s exact makeup. “The act of spontaneous fermentation isn’t as important as the flavor,” he maintains. “Whatever’s there is there.”
Jeff O’Neil, brewmaster at the Ithaca Beer Company, began playing around with native microbes when White Gold, a beer he intended to be a Belgian catchall, accidentally picked up some local bacteria. The beer was supposed to be a wheaty, golden farmhouse ale. Six months after bottling, it started showing a pineapple character. “I have no idea what it is or where it came from,” he says, “other than it’s bacteria, and it does something we like.” The funky character grows with each successive batch, as O’Neil primes new batches with a keg of its predecessor. The success of White Gold, along with beers like Russian River’s Beatification, inspired O’Neil to take a run at a Lambic-inspired beer. Unlike traditional Lambics, O’Neil’s spontaneous experiment goes into the barrel hot; but like Cilurzo, O’Neil believes the mini-ecosystem bred by his sour beers helps push spontaneous fermentation along.
“Conventional wisdom is that the conditions for these beers only exist around Brussels,” O’Neil says. “I didn’t know what to expect, but we got something similar” to a Lambic.
“A lot of brewing, to me, is intuitive,” O’Neil adds. “The textbooks we all read were written from the perspective of brewing industrial lager. Experimenting is a big part of the very broad canvas we all paint on. We’re going totally low-tech with these beers. It’s a traditional way of brewing. It’s not extreme. It’s a departure, but back in time.”
Modern Belgian breweries like Cantillon have proven that brewers can craft world-class beers relying on pre-industrial techniques. Allagash, Russian River and Ithaca have proven that Americans can harness native microbes to create styles that rival their Belgian counterparts. Back in Chelsea, Mystic Brewing wants to systematize what their American colleagues are doing, and isolate the most beneficial native yeasts floating around New England.
From the hundreds of wild yeast strains Greenhagen and his head brewer, James Nicholson, have pulled off of overripe pieces of fruit, the Mystic team has found three intriguing native strains. One came from a local grape, another from a farmer’s market plum. They found the most promising strain feasting on blueberries at Nicholson’s family home in Maine. Their favorite native strains have created dry beers with nice fruity noses, with plum and grape notes. But they’ve also created strange new flavors; it’s nothing Greenhagen can categorize, other than to say they’re distinct, tasty and mysterious. “It turns out that our native yeast has been super-distinct,” he says. “It doesn’t taste like anything else.”
Saccharomyces cerevisiae: Ale yeast rises to the top of the wort to ferment, creating a thick, yeasty head. Ale yeast strains work best at temperatures ranging from 50 to 75°F, and some strains will not actively ferment below 33°F.
Saccharomyces pastorianus: Lager yeast ferments at the bottom of the wort at colder temperatures (typically between 40-45°F). Lager yeast was first isolated at the Carlsberg Brewery in 1883. It’s a hybrid of two kinds of yeast that’s believed to have been created as yeast adapted to cold conditioning in Germany.
Wild-fermented Lambic-style beers are exposed to the open air during the cooling of the wort to allow natural/wild yeast and bacteria to literally infect the beer, a practice with roots in Belgian brewing. One of the typical yeasts involved is the Brettanomyces Lambicus strain.
Yeast cells survive and multiply by eating sugars in the wort, metabolizing them and expelling ethanol, carbon dioxide and other by-products that impart flavor and aroma. At higher temperatures, more of these by-products are created, which is what gives ales their characteristic fruity esters and spicy phenols. Lagers ferment slower and have cleaner flavors that are determined by the specific strain and the temperature at which it ferments.
Before Louis Pasteur isolated yeast in the mid-19th century, no one understood what caused fermentation. The Reinheitsgebot of 1516 didn’t even include yeast in its list of pure ingredients.
English Yeasts: English yeasts have developed to leave a malt forward profile with high levels of fruity esters. Some strains leave behind another fermentation by-product called diacetyl that, in small amounts, gives beer a slight buttery or butterscotch character. In large amounts, diacetyl is considered a flaw.
Belgian Yeasts: The unique profile of Belgian yeast strains is the defining characteristic of Belgian beers. These yeasts produce beers with a particular combination of banana- and cherry-flavored esters with black pepper phenols that I describe as “cotton candylike.”
German Wheat Yeast: Once again, the ester and phenol profile of these beers defines the style. Strong banana and clove characters which comes together as “bubble gum” or “circus peanut candy,” are the hallmark of these strains. These are low flocculating yeasts, meaning that they stay suspended in the beer, giving it a cloudy appearance.
American Ale Yeasts: American ale yeasts are known for their clean, low ester and phenol profiles. When fermented at the low end of their temperature range, they can be used to create lager-like beers. ■