“Infected” is rarely a word you want associated with your food or drink. But for hundreds of years, from Belgium to Iowa City, brewers have been cultivating the perfect cocktail of microbes to infect their beers and serve an ever-growing fan base.
Characterized by an acidic or tart flavor, sour beers can taste like everything from a dry wine to melted SweeTarts. Plain and fruited sour beers in the Berlinner Weisse, Gose or Flanders style have made their way onto many craft brewery menus, catering to drinkers who may not go in for the wheat, hops or malt flavors common in “clean” beers.
“It’s kind of like spicy food or something where it seems counterintuitive on some level, but it keeps bringing you back because it’s such an impactful flavor,” Head Brewer Andy Joint of Iowa City’s Big Grove Brewery said. For Joint, sour beer was an acquired taste, but after falling for New Belgium’s La Folie, he came to appreciate the science of sour brewing.
One bacteria, yeast, is essential to the production of all beer—yeast ferments grains to produce alcohol and carbonation—but exposure to anything but pure yeast can cause the release of enzymes and proteins that turn beer sour, for better or worse.
The trick is to introduce the right strains of bacteria for the right amount of time.
Traditionally, this means leaving a beer and a culture in a barrel together for years on end, allowing the beer to spoil to perfection, then mixing old and new versions of the beer (usually one-, two- and three-year-olds) together—a volatile process that, even when successful, doesn’t result in a high volume of product.
“[Sours] are really unique, they’re not like anything else in the beer world,” Big Grove brewer Jason Seiler said. “To get a good one you know that whoever’s making it really knows what they’re doing.”
Big Grove operates a facility in Solon where experimental future sours—some in barrels that have been reused multiple times in order to preserve tried and true microbial colonies—inoculate. Staff must change their clothes and wash completely before going from the barrel room to the brewery, or risk contaminating batches of clean beer.
The relatively new process of kettle souring has made this process quicker, cheaper, more efficient and more consistent—even if it lacks the art and nuance of barrel aging. For Big Grove’s kettle-made Sidehill Sour, brewers mash and prepare the grains as per a typical brew, then introduce the culture Lactobacillus (or “lacto,” common in yogurt-making). They monitor changes in pH levels, and when the beer has reached the desired acidity, usually after three or four days, they boil and kill off the bacteria.
This strategy has been utilized by local breweries, especially to produce Berliner Weisse, a low-alcohol lacto beer. In Germany, bartenders will serve Berliner Weisse with woodruff- or raspberry-flavored syrups to temper the tartness; Iowa brewers have their own takes.
Big Grove will occasionally whip up Que Onda Roja, a cherry and caramel sour, or mix a batch of Sidehill Sour with blackberry or other fruit. Coralville’s Backpocket Brewery makes the seasonal sour Pucker Up Right Meow, flavored with apricot and peach puree. And you can sometimes find the Strawberry Rhubarb Diddly, a Flanders-inspired sour, at Iowa Brewing Company in Cedar Rapids.
Breweries across the state are also keen on these sweet, sour, gorgeously-colored beers. Waterloo’s Singlespeed Brewery has used blueberry, peach, apricot, hibiscus, raspberry and elderberry in their sours; Exile Brewing of Des Moines adds passion fruit, pink guava, papaya, grapefruit and strawberry; Decorah’s Toppling Goliath and Pulpit Rock breweries offer a dragon fruit, mango and passionfruit sour and a raspberry Berliner Weisse, respectively.
Sour beers rarely make it into a bottle, in part because craft breweries haven’t been able to keep up with Iowans’ newfound thirst for them. Still, you can find six-packs of Exile’s Beatnik Sour and Peace Tree Brewery’s Kiss from a Gose at Hy-Vee stores and John’s Grocery. John’s also stocks beer from European sour producers, including Belgium’s Boon Brewery and Denmark’s Mikkeller. These intricately-flavored, lip-puckering draughts raise infection to an art form, and continue to inspire breweries like Big Grove to expand their sour beer program.
“It’s still a new realm in the Iowa brewing industry, but collectively we’ll get there,” Seiler said.
Of course, enthusiasm from customers is encouraging as well. Joint told the story of taste-testing a Big Grove sour with beer novices, and being surprised and inspired by their reactions.
“I didn’t think they’d care for it at all,” he said. “But there were several in the crowd that were like, ‘This is the best beer I’ve ever had,’ ‘This is like nothing I’ve ever tasted,’ ‘I didn’t know beer could taste like that.’ Chasing that, seeing that reaction, is fun.”