Not only can sour fermentation be applied to any number of beer styles, but it’s also achieved using a variety of techniques. Here, some of the country’s most talked-about sour-beer brewers weigh in on how they do it.
Sour beers are hot and fashionable right now,” says Phil Markowski, the brewmaster at Two Roads Brewing in Stratford, Connecticut. “American brewers are now leading the charge, applying sour fermentation to all sorts of styles of beer.”
All About the Base
At The Rare Barrel, an exclusive sour brewery in Berkeley, California, the beers begin as three base ales named after their colors: gold, red, and dark. “We brew the beer, wait three to six months and then taste the base beers without any additions,” says Jay Goodwin, the cofounder and director of brewing and blending. “Then we sit down with several fruits, spice tinctures, and other ingredients and evaluate the beer for strengths and weaknesses and decide what works best. Along the way, we’re trying to take copious notes to explain how we made these flavors.”
The base beers at The Rare Barrel are usually fermented with Brettanomyces yeast and Lactobacillus bacteria during primary fermentation in stainless steel. Two to four weeks thereafter, the beers are transferred into oak barrels where they age from three months to six years. All of The Rare Barrel’s beers are blended—whether from barrels within the same batch or barrels from many different batches—as the final step before serving. “Blending lets us dial in variables such as acidity and balance to produce beer that we love,” Goodwin says.
“Through all these fermentation experiments, we start to learn more and more about all these different processes; we add new tools to our tool belts. We take these shots in the dark, then look back and evaluate, and use that knowledge to proceed.”
Brett-Lacto primary fermentation is one good way to make sour beer, Goodwin says, but it’s not the only way. “I’d say the most common method is Russian River Brewing Company’s,” he speculates, “in which you ferment with a brewer’s yeast and make sure there’s a lot of residual sugar post-primary fermentation, basically trying to save food for wild yeast and bacteria to eat later.”
From there, that “Russian-River method” involves adding those wild yeast and bacteria in secondary in an oak barrel and letting that beer age in the oak barrel for a period of time. The trouble with that method—especially for homebrewers—Goodwin explains, is that wild yeast and bacteria aren’t always strong enough in that secondary step and don’t yield as complex beers. “Russian River has been growing its culture for a long time. It’s extremely strong,” he says. “So while it makes sense to emulate the people who are doing it best, brewers can’t just buy a mixed culture and expect it to be as flavorful as Russian River’s.”
Another method of souring beers that Goodwin is noticing among breweries is hot-side wort souring, also known as sour mash or kettle souring. “It’s basically introducing bacteria so you infect wort with Lactobacillus, letting the beer get as sour as you want. You follow that with a boil to kill off all the Lacto. Then you send it to the fermentor with brewer’s yeast, achieving acidity in a shorter amount of time.”
Goodwin recommends kettle souring for brewers or homebrewers without the storage space for barrels. Not only will it save room, but it will also create fewer infections in the beer.
The Solera Approach
Two Roads sours some of their beers using the solera method, in which a portion of the aged beer is drawn out of a barrel—or series of barrels—containing the sour culture, while fresh beer is added. For Two Roads, this method is an attempt to keep a complex stew of wild yeasts and bacteria in relative balance. “We’re trying to keep the culture in constant motion,” says Phil Markowski. “We keep it fed, pull off of it, run fresh beer in, and keep it going so that we get as repeatable a result as possible from batch-to-batch. These cultures are finicky and act in concert with each other. We’re trying to maintain that harmony and not have one particular microbe dominate the others.”
One of the harmonious sours is Two Road’s Urban Funk, a beer fermented with airborne yeast captured during Superstorm Sandy (the 2012 Atlantic hurricane that wreaked havoc). “We have a multitude of organisms in that stew,” says Markowski. “It’s taken on a life of its own, and we are trying to keep the various cultures in balance.”
Urban Funk, a member of Two Road’s Captured Yeast beer series, was fermented entirely in stainless steel to give the beer an “urban character.” Next in the series is Country Funk, a beer that will be fermented with yeast captured in a rural setting and aged in barrels “for a more rustic example of sour beer.”
“Maybe someday there will be a Suburban Funk,” Markowski says, only half joking. “We’re continuously experimenting with new cultures that we capture.”
“We don’t try to rush the sours; that’s my philosophy. It takes a while but it’s worth it.”
At Commons Brewery in Portland, Oregon, Head Brewer Sean Burke relies on a local yogurt company to provide the sour culture for the Biere Royale, a sour ale brewed with black currants. “Yeast labs are very nice for providing cultures for pitching, but they tend to be expensive, and rightfully so,” he explains. “In the case of our Biere Royale, I was able to go to the local grocery store and spend $1.69 on our Lactobacillus culture.”
That’s right—Burke is souring beer using unpasteurized Greek yogurt from Nancy’s Yogurt in Eugene, Oregon. He’d been experimenting with kettle souring, and it dawned on him one day that his favorite yogurt was pack full of strains of Lactobacillus casei.
“To my knowledge pre-primary fermentation acidification always involves Lactobacillus, and Lactobacillus casei is a known brewery spoiler. I thought, Why not? I’ll try to sour the beer with yogurt.”
And so he did. He brewed Biere Royale (with pilsner, malted spelt, flaked wheat, acidulated malt, Saaz hops, and eighty-eight pounds of black currants in a 7-barrel batch), ran it into the kettle, poured some yogurt in, and let the beer sit for three days. “That beer dropped to a very nice pH—not too low, but to a level we liked where we then killed off the Lacto in the boil,” he remembers. Burke then fermented Biere Royale with a clean ale strain, and the brewery’s popular yogurt beer was born.
“There are 100 ways to make sour beer, each one totally different,” says Walt Dickinson, the head blender at Wicked Weed in Asheville, North Carolina. “If you’re going to make sour beer, you need to pick a direction that feels right to you.”
All of the sour beers at Wicked Weed are 100 percent Brettanomyces primary fermented. “Brett is such an important component in the balance of the beer,” Walt explains. “There’s a lot of residual Brett character to our beer because it’s a base that carries fruit and the acidity well. We create less acidic, softer beers than most.”
After Wicked Weed’s beers ferment with Brettanomyces, Walt and his crew blend in aged sour beer to inoculate with souring bacteria. Black Angel Cherry Sour, for example, is brewed with more than a pound of sweet and tart cherries per barrel. It is then aged with souring bacteria in bourbon barrels and blended with other barrels of the same vintage. “Black Angel might come out one time with really heavy cherry esters; the next it might have more barnyard funk,” Walt says. “We’re trying to make beer as consistent as possible—that’s where blending comes in.”
It’s difficult to make sour beer, especially as a homebrewer, because blending is such an important step in the process, Walt explains. “You can do everything to emulate what the beer is going through in a barrel,” he says, but without multiple barrels for blending, it’s challenging to create well-rounded flavors that are consistent over time. Despite those challenges, though, Walt’s romanticism for and dedication to his craft is creating some of the country’s most talked-about and award-winning sour beers. “I’m very enamored with Brett beer, and sour beers specifically. Fermenting in the barrel is beautiful,” he says.
“We’re homebrewers,” Walt adds proudly. “That’s our background. I learned how to work with bacterias and Brett in a homebrewing environment. That’s where I cultivated my ability to work with yeast. Yeast strains are really challenging—the wildness brings unpredictability. It makes brewing beer a journey, and I love the unknown of it.”
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PHOTO: MATT GRAVES