Karl De Smedt keeps watch on 124 sourdough starters at the Puratos Sourdough Library in St. Vith, Belgium. His collection comprises cultures gathered from around the world, and he can’t establish which is the oldest. “If somebody tells me I have a 500-year-old sourdough, I have to believe them,” he says.
Last year, he traced one route sourdough took during America’s 19th-century gold rush, starting in Seattle, traveling to Alaska, and on to the Yukon to acquire cultures used to create bread for perhaps 150 years. He picked up one he labeled “106” in Whitehorse, stored in a jar bearing a typed message, “100-year-old Yukon sourdough starter — DO NOT THROW OUT,” on the top. Former Canadian Senator Ione Christensen still keeps it in her refrigerator.
Bread is one thing, but the history of the mixed cultures used to put the sour in American sour beer is startlingly briefer, barely extending back into the 20th century. Evidence resides in the basement of a former brewer’s house in Boone, North Carolina; in a photograph of giant glass bottles at Russian River Brewing Company in Santa Rosa, California; in the cellar at Cambridge Brewing Company in Massachusetts; and certainly in wood at New Belgium Brewing in Fort Collins, Colorado.
Hundreds of breweries today sell sour beer, many of which boast about using their own, unique mixed cultures. Few of them were making beer 15 years ago, of course, and, for the ones that were, fewer still had reason to trust their wort to anything but Saccharomyces cerevisiae (the typical brewing yeast that ferments so-called “clean” beers).
Mixed cultures may contain Saccharomyces cerevisiae, but most also feature souring bacteria and wild yeast, including Brettanomyces, Lactobacillus, and Pediococcus. Yeast labs made a few of those microbes, affectionately referred to as “bugs” or “critters,” available to commercial brewers beginning in the 1990s, while some brewers hunted them down themselves—whether by leaving wort in open containers like coolships to be inoculated by what was in the open air, or by collecting wild yeasts and other microbes found in the wild, or by culturing the yeasty dregs found at the bottom of other bottles.
Many of the cultures used to make the first American sour beers have since been lost to history. Perhaps surprisingly, given that microbial communities are always dynamic and shifting, some of the cultures used to make pioneering beers are still around.
They also remain untamed. “I just had a foeder turn, seemingly overnight,” says Lauren Limbach, the wood cellar director at New Belgium Brewing, in reference to a foeder she calls Vader, which went from producing pleasant flavors to being a “vinegar bomb.” “I can’t tell you what happened. No smoking gun. Right when you think you know, you don’t. They’re not domesticated.”
The challenge, it turns out, is not only in finding a combination of microbes that create pleasingly sour beer, but in keeping them contented. Ron Jeffries at Jolly Pumpkin Artisan Ales in Dexter, Michigan (the first American brewery, starting in 2004, to produce only barrel-aged, mixed-fermentation beers) figured out long ago that such cultures are best treated as active collaborators rather than inert ingredients.
“I used to think I should bank it. I couldn’t afford to, and when I could I realized I didn’t want to,” he says, referring to the practice of sending a single strain or a mixed culture to a laboratory to be stored. In theory, if a culture suddenly begins producing different flavors than before, a brewery can retrieve the banked strain from storage. The practice is similar to creating a restore point before installing new computer software.
“That seems very ‘Westworld.’ I like to think of my yeasts as living things,” he says. “I’m not controlling the yeast; I am listening. This is the yeast saying, ‘This is what I need to be happy.’”
Although few drinkers realized it at the time, Wisconsin’s New Glarus Brewing Company began selling sour beer in 1994, brewed using traditional practices co-owner Dan Carey had learned in Belgium. To make Wisconsin Belgian Red, first released about a year after the brewery opened, he transferred the beer to a lauter tun, rather than a traditional coolship like he’d seen in Belgium, so it’d be exposed to air and inoculated by wild yeasts and bacteria overnight. “We opened all the windows and came back the next morning,” he said. “It was always a little scary. We’re making Lager beer, we shut down the bottling line, open up the brewery. You learn microbiology very quickly.”
Though coolships are now relatively common—dozens of brewers have installed them, particularly since Allagash Brewing in Maine christened its own in 2007—in 1994, “spontaneous fermentation” meant nothing to all but a few American beer drinkers. Back then, if a beer was sour, something was wrong with it. When the first batch of New Glarus’ Belgian Red sold out in four days, for all customers knew, the 1.4 pounds of Wisconsin-grown Montmorency cherries in each bottle were the reason the beer tasted tart. Talking to a reporter for The Capital Times in Madison, Carey simply said that the Belgians used “natural yeast” and New Glarus did as well.
Carey first became intrigued with sour fruit beers in 1985 while he worked as an intern at Ayinger Privatbrauerei in Germany. He and his wife Deb, who raised the money to open New Glarus and who currently serves as president, made a trip to Belgium with their two young daughters. They knocked on the door at Brouwerij Lindemans outside of Brussels, and René Lindeman answered the door. “Here Deb and I are with two little girls and he shows us everything,” Carey says.
Carey spent six years perfecting his own way of making such beers, tinkering in what little spare time he had while working as a brewing supervisor at Anheuser-Busch. Belgian Red was one of the reasons that Deb suggested they open their own brewery. “This will put us on the map,” she said at the time, and the dozens of national and international awards it won in the first years after it was released suggest she was correct.
One of the first purchases the brewery made was two large, upright wood tanks from Rodney Strong Vineyards to age the beer in. As New Glarus added more wood tanks, brewers would sometimes inoculate one with portions of another. “Sour beers are very much alive and ever-changing,” Carey says. “Our microflora has evolved every year since since 1994, as we encouraged their proliferation in wooden tanks as well as in the oak ceiling of our coolship room.” The brewery opened a separate facility, with a traditional coolship, in 2014, and calls it the “Wild Fruit Cave.”
While Carey emphasizes the importance of tradition in brewing such beers, other burgeoning sour brewers had to fill in knowledge gaps with their own innovations. Belgian Amber Framboise, made by Cottonwood Grille & Brewery in North Carolina, was the first sour beer to win a medal at the Great American Beer Festival, capturing a bronze in 1995. And Gueuze (a name most breweries would have second thoughts about using today) made by Joe’s Brewery, an Illinois brewpub without a mash tun, earned three out of four stars from renowned beer writer Michael Jackson in the 1997 edition of his Pocket Guide to Beer.
Kinney Baughman, who stands 6’8”, was playing club basketball in Belgium in the late 1970s when he discovered he liked beer, including sour beer. He took up homebrewing when he returned to the States and saw an ad in Mother Earth News. Later, he developed and sold homebrewing equipment while teaching philosophy at Appalachian State University.
Meanwhile, a restaurateur at Boone’s Cottonwood Grille & Brewery had begun making five-gallon batches of beer in a small house behind his restaurant, but nobody was buying the obviously infected beer. “The stuff was awful,” Baughman says. “They couldn’t give it away.”
He cleaned up the brewery and soon was brewing larger batches—first 30 gallons at a time, then 60, and eventually 120. “We were running out of kegs,” he says. He grabbed a few five-gallon kegs from his basement, ones he hadn’t used in years, and some of which still had beer in them. He didn’t realize the sanitizer he used to clean them would not kill Pediococcus, a lactic acid bacteria that sours beer and had grown in those kegs. Within weeks the beer was noticeably tart and about to taste even more sour.
“Anybody else probably would have thrown them out,” Baughman says. Instead, remembering what he tasted in Belgium, he began blending, mixing sour beer and fresh, clean beer with raspberry concentrate. “I thought it was time to show Boone what a Belgian beer tasted like.”
He entered two of his sour beers in GABF blind judging: Amber Framboise in Belgian-Style Specialty Ales and Black Framboise, a Sour Stout, in Fruit Beers (GABF did not add a Belgian Sour category until 2002). “When we submitted the beers, the Amber was young and evidently matured to perfection by the time they judged it,” he says. “The Black Framboise was perfect when we put it in the bottle and was probably too sour for the 1995 judging palate.”
Baughman continued brewing commercially for only a few more years, and works today as director of information technology at Appalachian State. He still has kegs of “Carolina Culture” in his basement, and used some of it last year to inoculate a batch of lacto-fermented peppers, a new personal obsession. “The peppers turned out fine. Entirely different flavor from my other hot sauces,” he says. “Deep inside, you can still taste those beers of old.”
While Baughman was experimenting with his Belgian-inspired beer in North Carolina, John Isenhour was doing the same in Illinois. Isenhour joined the American Homebrewers Association in the 1970s and was assigned number 3,413; these days new members get six-digit numbers. He worked as an assistant and then head brewer at Joe’s Brewery while he completed his doctorate in informational science at the University of Illinois. Joe’s was more student bar than brewery, which gave him the freedom to make what he wanted.
The first time Isenhour walked into Joe's in 1994, he asked what beer was on tap. “Bud, Bud Light,” the server answered. “I thought you made beer here,” Isenhour said. “We got that stuff over there,” the server said, gesturing toward the brewpub's handles tucked inconspicuously behind taps for beers sold at student-friendly prices.
He collected the microorganisms to ferment the sour beer Champaign–Urbana-area farmers took to calling “Belgian lemonade” when he volunteered to pour at a Chicago Beer Society tasting event. He attended that event specifically to talk with special guest Pierre Celis, the former milkman who is credited with reviving the Witbier style in his native Belgium in the 1960s. “There were a bunch of Lambics and back then they all had dregs (living microbes),” Isenhour says. “So when one bottle was almost empty I would pour the dregs into a bottle, and collected almost a full Champagne bottle of dregs.”
Isenhour had a dedicated yeast culture room in his house in Urbana. He made three five-gallon batches of beer over the course of a few weeks, yielding cultures that were in three different “phases.” He pitched those into seven barrels of wheat malt extract at Joe’s, and added a small amount of aged Saaz hops. The brewery was not built to mash grain traditionally. (The local homebrew club tried to help make a massive unmalted wheat mash addition on one batch, but it burned on the bottom and the runoff stuck solidly. “I lost tradition points there but was always trying to get past the simple extract to add complexity,” Isenhour says.)
He doesn’t remember when Michael Jackson tasted his beer, but by then it had a reputation of its own. Isenhour was invited to talk about sour beers at the 1997 Craft Brewers Conference in Seattle, although that was about the time that the owner of Joe’s told Isenhour he was replacing the brewery with a widescreen television. The bar, which even today goes by the name of Joe’s Brewery, initially kept the kettle as a showpiece. Isenhour had just started a new batch of Gueuze. He bought, and later sold, most of the equipment, and eventually took 14 kegs of the Gueuze with him.
He still has one of those kegs today. “Someday I’ll have to see how it is doing,” he says. He recently retired as chief technology officer at Kennesaw State University, where he also taught classes on the scientific and cultural aspects of brewing.
New Belgium’s former brewmaster Peter Bouckaert already understood how to make sour beer on a larger scale than other Americans when he left Brouwerij Rodenbach in his native Belgium in 1996 to direct operations in Fort Collins. In 1998, he began assembling the culture Lauren Limbach oversees today.
[Disclosure: New Belgium Brewing underwrites Good Beer Hunting’s Into the Wild series.]
Back in 2000, when he rolled up what looked to be a giant garage door at the brewery, revealing row upon row of wine barrels stored a safe distance from where “clean” beer was fermenting, he made it sound simple. “We figured 12 barrels, OK, buy 12 barrels, then why not buy 12 more?” he said.
By then there were 79 barrels, and the brewery had recently taken delivery of four large wooden casks called foeders, which stand upright and hold 60 hectoliters (1,585 gallons) each. New Belgium bottled the now-legendary La Folie for the first time only a few months before.
By the time Michael Jackson visited only 16 months later, New Belgium had added six 130-hectoliter foeders. Jackson described the brewery as “The Rockies’ rival to Rodenbach.” These days, New Belgium has 66 such vessels in its “Foeder Forest.”
Bouckaert, who retired from New Belgium in 2017 to help start a small brewery called Purpose Brewing & Cellars, filled the first wine barrels in 1998 with standard beers from the brewery’s portfolio, as well as special ones designed to provide different nutrient levels. He inoculated them with microbes purchased from labs, fresh Belgian-made Lambic, and sometimes with what was found in kegs returned to the brewery. He and others at the brewery tasted the results every 14 days.
“It’s not a strict science. There are judgment calls—Why do this?” he said. “I don’t know—I think that’s the best way, that’s why.”
He chose 20 barrels for the first bottling, and the event turned into an in-brewery party. Bottles were hand-corked and hand-labeled, and then Bouckaert numbered each one. A few months later, the first foeders arrived.
Limbach worked in sensory at the time, and was on the first team of panelists that regularly sampled from the barrels. When the foeders were ready to fill in 2000, Limbach tasted through all 79 barrels to pick the ones that would be used to seed the foeders. “The concept was, ‘This will be our strain.’ I was looking for 40 hectoliters; 20 of the small barrels,” she says. “All the best things about our beer for the first foeders.”
The process of filling a new foeder, or more often refilling a recently emptied one, is very different than how New Belgium adds yeast to ferment most of its beers. For the latter, brewers add a quantity of a single strain of Saccharomyces cerevisiae, most often freshly propagated at the brewery, to wort.
Empty foeders, however, are filled with filtered beer fermented with a Lager yeast strain and what Limbach simply calls an “inoculant”: living beer with the mixed culture, pulled from another foeder. “What are my options?” Limbach asks herself. “They are always different. That inoculant is very time-sensitive.” Although the microbes within each of the 66 foeders are the same, as cultures they are in different stages of development. “You want to know, at the very moment, who is winning. You want to find the community that is happy, is in a state of growth,” she says.
She knows the microbial communities and the wood they live in intimately, and calls the foeders by name. “Vader turned and Piña didn’t,” she says. Those two sit side-by-side in the Foeder Forest. Mentally, she divides the entire foeder facility into six quadrants and expects the foeders within each section to act alike, although they remain individuals. The same is true of barrels.
One of them, labeled pH1, has become beer famous. Limbach thought the barrel, one of the first in New Belgium’s collection, had been lost when it disappeared in 2003. Two years later, she spotted the barrel at Russian River Brewing in Santa Rosa, California, learned that Bouckaert had given the barrel to co-owner Vinnie Cilurzo, and was delighted it hadn’t become a planter. Cilurzo continued to use the barrel, and he and Limbach told its story many times. Jay Goodwin and Alex Wallash, who were in the process of opening a brewery, heard about the history and decided to name their Berkeley, California, brewery “The Rare Barrel” in its honor.
Not long after The Rare Barrel opened in 2013, Cilurzo shipped pH1 back to Fort Collins. It didn’t stay long, because Limbach sent it to Berkeley for Goodwin and Wallash to use. After Bouckaert announced he was leaving New Belgium, they hand-delivered pH1 to him at his new brewery. He suggested it wouldn’t be the last stop.
Limbach says the ongoing story would make a great movie, but an empty barrel is not how she’d choose to ship an inoculant. She credits the barrel itself, and the caliber of breweries it has spent time with, for the legend, rather than any microbes that might have hitched a ride. “There’s something that happens in a barrel. You get to know it. It has a personality,” she says. “It’s like any relationship. These barrels are alive. It is always a conversation between the two of you. It helps you be a better friend.”
“There’s probably some pH1 in there,” says Vinnie Cilurzo. He’s looking at a photo taken in 2006 in the barrel room of Russian River’s Santa Rosa brewpub, and points to a glass carboy with “Beat” written on it. “Beat” stands for Beatification, and the first batch of the beer was aged in the storied pH1 barrel.
The carboy is one of a dozen of various sizes in the image. What amounts to a family photo shows how quickly things changed after he and his wife and business partner, Natalie, bought the Russian River brand and opened the pub in 2004. “Pedio” is written on one carboy, “Brett-claus” on another. The words “spontaneous, no mash tun, open ferm in barrel room” wrap around the neck of another, and one’s labeled “Lacto”—and the beat goes on.
The microorganisms he chose more than a dozen years ago provide the foundation for what he calls the Russian River bacteria blend. Cilurzo first brewed a beer with Brettanomyces, Temptation, in 1999, back when the brewery was located in Guerneville and owned by Korbel Champagne Cellars. He fermented the beer with clean yeast, then aged it in Chardonnay barrels with Brett.
He began using the blend in Supplication, the second barrel-aged beer in what has become a family. After primary fermentation with Saccharomyces cerevisiae in stainless steel tanks, the beer is transferred to Pinot Noir barrels, along with Brettanomyces and sour cherries. After about three months, brewers add the bacteria blend, made up primarily of Pediococcus and Lactobacillus.
He originally stored the blend in a carboy, then a keg, and since 2008 in plastic totes. “We could never run out of bacteria,” he says.
The process has changed at Russian River’s new production facility, which has a coolship. “It is a true mixed fermentation,” Cilurzo says. For instance, after a batch of Temptation is brewed, as always with aged hops, about a third of the wort is pumped to the coolship. The other portion is fermented with Saccharomyces cerevisiae in stainless steel. The following morning, the cooled wort from the coolship is blended in with the beer fermenting in stainless steel. After primary fermentation is complete, the blend, rich with bacteria from the coolship, is transferred into barrels. “So far I’m liking the flavor,” he says.
His focus is on maintaining flavor, not adhering to a particular process. “Temptation is tasting great now. 2010, 2012, it was too sour. I let things get away,” he says.
Not long ago, Tomme Arthur at The Lost Abbey in California came across a barrel he received from New Belgium, at roughly the same time Cilurzo acquired pH1. “It’s still making good beer,” he says.
Arthur first struck up a partnership with Brettanomyces when he created Cuvee de Tomme at Pizza Port Solana Beach in 1999, and it since won five GABF medals in three categories for two different breweries. (Arthur took the beer with him when he helped found The Lost Abbey in 2004.)
Arthur also talks about finding a process that serves flavor. “There is a basic premise in-house that Cuvee is Cuvee,” he says. The Cuvee culture, which began with three different types of Brettanomyces and has since continued to evolve, is one of three that’s unique to The Lost Abbey. Another is used for Red Poppy, a luscious dark beer made with sour cherries, and Arthur uses the third for his other sour beers.
“We do selective culturing. We only take from the barrels we use in a blend,” he says. When it comes time to package a beer, Arthur and members of his staff will evaluate perhaps 50 barrels. 45 of them may end up in the final beer, but they will harvest the slurry to refresh the culture from only the best of those. “We pick the ones that are a pure expression of the beer. That’s what we are going for.”
15 years ago, there were few other brewers to ask about the care and keeping of sour beer cultures. Nor were there other resources. “They didn’t write books about it. There weren’t websites like Embrace the Funk,” Cilruzo says.
In 2003, when Will Meyers at Cambridge Brewing Company in Massachusetts told two friends who oversaw operations at much larger breweries he was going to use his brewpub lauter tun for a 72-hour “sour mash” to create a lactic fermentation, they warned him he might contaminate his brewery so badly it would never recover. He wasn’t sure if they were kidding or not.
Meyers filled a single wine barrel with some of the wort from that batch and added Brettanomyces, along with cherries. He still makes Cerise Cassée today, and that barrel, named Carl, is integral to Cambridge’s solera-style fermentation system. “We quickly realized that the Brett expression was much more interesting, complex, delicious than the ‘clean’ sour mash beer,” he says. “And while we continued with the sour mash method for several years, all of the beer went through the barrels, which grew to contain cultures from multiple sources.”
Cassée is a product of three sets of wine barrels that age in the stonewall cellar beneath the brewery. Meyers packages beer from the oldest third of the barrels, replaces that with beer taken from the second oldest set, uses beer from the youngest set to fill those barrels, then fills that with fresh wort.
“We have not added any cultures to the solera in at least a decade. We do add dregs (from interesting bottles) on rare occasion to other barrels, but the solera is its own creature and we do not mess with the biosphere and the balance of cultures it has created for itself.”
Dregs remain a popular part of the mix when brewers want to create their own culture. Brandon Jones at Yazoo Brewing understands when brewers contact him to ask if Yazoo pasteurizes its sour beers (like New Belgium), or uses a strong wine yeast when bottling. The brewery does neither. “I’ve been there,” he says.
Jones started the Embrace The Funk website in 2011 and has been near the center of online discussions about sour beer fermentation since. There are literally hundreds of brewers for each one interested in mixed cultures 15 years ago.
Yazoo has two souring mixed cultures, one used mostly in blonde beers and the other in dark. “They culminated in Mason jars from my homebrew days,” he says. “Some of that comes from bottle dregs. I would be talking to brewers and ask where they got this Brett from, where that Lacto came from, if they used Champagne yeast or it was straight bottle-conditioned. People like Bob Sylvester [at Saint Somewhere Brewing in Florida] were great. He told me everything he knew and that he did with the beer.”
He understands there are differences between knowing what comprises the culture and how it will behave in beer. “Sometimes these cultures keep evolving,” he says. “I feel like they’ve established how they’ll act. You start learning what to expect. In the summer it can get more aggressive, acidic.”
Yazoo is part of an anonymous study Creature Comforts Brewing Co. in Georgia began last year, which is using genetic sequencing to better understand mixed cultures, including 37 samples from 18 breweries. Analysis of the data has only just begun, and three other laboratories have agreed to collaborate.
“We’re demystifying everybody’s mystery,” says Creature Comforts quality manager Daniel LePage. The list of what he expects to find is rather long, the sorts of things you’d expect to see when a brewer hands a wish list to a microbiologist. “We’d like to find out what’s in our culture. What it likes,” he says, beginning to sound like a brewer. “That way we can be good parents.”
Some brewers, however, are fine with a bit of mystery. “If you had it all figured out this would be a spreadsheet,” Limbach says.
“That would be sad.”