Brewers’ Perspectives: Mad for Mixed Fermentation

Brewing with sour- and funk-inducing “bugs” presents its own challenges, as brewers from Jester King Brewery, Two Roads Brewing Co., Almanac Beer Company, and more, explain.

Emily Hutto Aug 12, 2017 - 7 min read

Brewers’ Perspectives: Mad for Mixed Fermentation Primary Image

Trending now are sour and funky beers, many of which are created by mixed fermentations of yeast and bacteria to replicate flavors associated with traditional farmhouse ales. To create these complex, nuanced, and often unexpected beers, craft brewers are fermenting beers with Brettanomyces and bacteria such as Lactobacillus and Pediococcus, among other microbes. Some are are even fermenting their beers with naturally occurring airborne yeasts and bacteria that they capture from the air.

Brett, Lacto, Pedio

The most common yeast-bacteria cocktail used in sour and funky beer-making is the Brettanomyces, Lactobacillus, and Pediococcus trifecta. Brettanomyces, or Brett, is a yeast strain that ferments more slowly than standard Saccharomyces. Brett has many different strains that yield a cornucopia of flavors and aromas, most notably barnyard funk and horse blanket. Brett creates earthy, fruit, and floral characters in beers as well. Lactobacillus and Pediococcus are bacteria that consume sugar and leave lactic acid in its place, creating tart and acidic qualities in beer.

“We sour our beers with intentional inoculation coupled with unintended organic fermentation that comes along with reused barrels,” says Douglas Dayhoff, the president at Upland Brewing Company in Bloomington, Indiana. “We inoculate our wood-aged sours with the combination of classic microbes—Brett, Lacto, Pedio. This helps us gain a certain amount of control before embedded microbes in the foeders and barrels further develop the beer’s character over time. We’ve seen the embedded microbes in that wood actually help accelerate and create better fermentations.”

The mixed microbes that ferment Upland’s sours create complexity that can’t be achieved with basic ale yeast, Dayhoff says. “We shoot for multiple dimensions of flavor and aroma that reflect a balance of malts, microbes, fruits, flowers, and spices. Our beers have pleasant tartness and cheesy-funky notes that express but then finish clean.”


House Blends

A house yeast blend is a thing of beauty among craft brewers, many of whom have gone to great lengths to create these microbial mixtures. At Jester King Brewery in Austin, Texas, the house yeast blend developed out of what Co-owner and Brewer Ron Extract calls “miniature coolship experiments.”

“We left a pan of wort to cool overnight and sent it off to a lab to isolate those yeasts. From there, we decided which yeasts to use, and [we] sourced various strains from commercial yeast labs. Over time, we created a unique blend. At this point, it is truly a house yeast—the blend of microorganisms is truly unique. When you have a mixture, it mutates and changes and becomes even more unique.”

Another blend that started out of thin air was created by Two Roads Brewing Co. in Stratford, Connecticut, when Brewmaster Phil Markowski and his team captured and isolated airborne yeast during Superstorm Sandy. “We have a multitude of organisms in that stew, and we’ve also added some lab culture to it. Now it’s a combination of something we caught airborne and some cultures that we purposefully added,” Markowski says. “It’s taken on a life of its own.”

This stew was used to ferment Two Roads’ award-winning Urban Funk sour ale that aged in stainless steel for a year before its debut in 2013.


Another noteworthy house microbe blend was cultivated by Jesse Friedman, the cofounder and brewmaster at Almanac Beer Company in San Francisco, California, with a combination of dregs from favorite sour beers. “We threw a party, and everyone brought their favorites. We cultured the dregs from those bottles and added commercial bugs as well. There are too many beers to name—of course, there was beer from Russian River, Orval, Cantillon ... at least a dozen or two.”

Spontaneous Fermentation

Spontaneous fermentation, in which beer ferments entirely from naturally occurring airborne microbes, is the original form of mixed fermentation. This ancient, open-air fermentation method yields the funky, tart, and sour flavors of traditional Belgian farmhouse ales. Spontaneous fermentation is time-consuming and inconsistent and, therefore, rare among American craft brewers. There are a few, though, including Jester King Brewery, Allagash Brewing in Portland, Maine, and Former Future Brewing Company in Denver, Colorado, that are home to small coolship projects.

There’s one pioneer brewery in Tillamook, Oregon, that is fermenting all of its beers via coolship. “We don’t pitch yeast. We are at the mercy of yeast and bacteria,” says Trevor Rogers, the co-owner at de Garde Brewing, who chose the site for his brewery based on where he could capture the most delicious and best-smelling microbes on the Oregon coast. “We are quite fond of the character of the microbes and naturally occurring yeast on the Oregon coast,” he says. “I’ve found that truly wild fermentation is an intuitive science. So much more of what we do is by smell and by taste and feel [rather] than by the numbers.”

The Benefits of Blending

All of the breweries here agree that mixed fermentation is often inconsistent and sing the praises of blending barrels after wood aging. “Different barrels yield different results, and that’s where blending comes in,” explains Markowski of Two Roads. “It’s hard to get a consistent and pleasant mouthfeel out of long-aged sour beers. That’s where moving in the direction of blending instead of single batches [really helps],” adds Dayhoff at Upland. Friedman of Almanac Beer Company can’t stress the importance of blending enough. “Blending is an opportunity to take different parts that create a whole. It’s part of the final editing process.”

From inoculation to open fermentation and everything in between, each brewery seems to have its own signature method for souring and funk-ifying beers. “There’s just not a lot of standard practice in the industry—every brewery has its own approach to the process and the flavor,” says Friedman of Almanac. Despite the varying approaches, though, these brewers all agree that mixed fermentation is a way to establish complexity and nuance. It taps a new frontier of possible flavor and aroma combinations and creates interactions among organisms that yield evolving characteristics over time.

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