Funkwerks’ 5 Tips for Kettle Sours

By Dave Carpenter

Funkwerks, a saison-focused craft brewery in Fort Collins, Colo., has racked up more than its fair share of awards since opening in December 2010. Co-founders Brad Lincoln and Gordon Schuck took home gold and silver medals at the 2011 and 2012 Great American Beer Festivals (GABFs), respectively, for their flagship Saison, and the brewery won gold for Deceit (a Belgian-style golden strong ale) and was named Small Brewing Company of the Year at the 2012 GABF.

In 2014, Deceit won a World Beer Cup silver and Raspberry Provincial took home GABF gold. Raspberry Provincial is a kettle sour, which is a beer that relies on bacterial souring pre-boil to achieve its tart, refreshing character. Unlike, say, traditional lambic, which requires months or years of aging with a mix of microbes to achieve a complex, funky sourness, a kettle-soured beer needs only a day or two to gain a pleasant lactic acid tang. The method isn’t ideal for Flemish red, oud bruin, and lambic-style ales, but it’s perfect for gose, Berliner weisse, and other “clean sour” styles that primarily exhibit a lactic character.

Gordon was kind enough to share his top five tips for brewing an excellent, even award-winning, kettle soured beer.

  1. Start with the wort. “Begin with a wort of modest gravity,” he says, “around 1.040. Make sure the lactobacillus has adequate nutrients and simple sugars. And no iso-alpha acids! Thoroughly clean your kettle, as trace amounts of iso-alpha acids will inhibit some strains of lactobacillus.”
  2. If you love it, kill it. “Raw wort has all kinds of stuff that can potentially ruin your sour wort, so boil it first [before cooling and pitching lactobacillus] to sterilize,” Gordon advises. In other words, you’ll boil twice: a brief boil to sterilize and then a longer traditional boil once souring is complete.
  3. Keep out oxygen. “Lactobacillus is an obligate anaerobe, meaning it can tolerate oxygen but prefers an oxygen-free environment. Purging with CO2 can also prevent contamination from airborne organisms.”
  4. Inoculate with pure culture. It’s possible to introduce lactobacillus by adding a measure of grain—which naturally hosts scores of lacto cells—to fresh wort. But other bugs also inhabit those kernels, and it’s hard to control the result. “I’ve had very good beer that was inoculated with grain,” he admits, “but I’m a firm believer in using pure cultures.”
  5. Time and temperature. “Different strains of lactobacillus prefer different conditions,” says Gordon. “Maintaining a temperature of 100° F (38° C) for 24 to 48 hours works for most strains.” Homebrewers may need to use a fermentation heater in order to maintain an elevated temperature in the kettle.

Using Gordon’s advice, we can break down the kettle-souring process as follows:

  1. Mash, lauter, and sparge (or dissolve malt extract in hot water) as you would for any beer.
  2. Conduct a brief boil of perhaps 10 to 15 minutes for sanitation purposes, and then cool the wort to 100° F (38° C).
  3. Pitch a culture of pure lactobacillus right into the kettle and cover. Allow the lacto to sour the wort over the next day or two, using a heater if necessary to maintain an environment that’s slightly warmer than blood temperature.
  4. When the wort has reached the desired level of sourness, return the kettle to the heat and boil for the customary 60 to 90 minutes, adding hops according to your recipe’s specifications.
  5. After the boil, chill and ferment with standard brewer’s yeast.

There you have it. If you’ve been itching to brew a sour beer but don’t have the patience to invest in months or years of aging that may or may not turn out a drinkable dram, try a refreshing Berliner weisse or gose. Using these proven kettle techniques, you’ll be savoring the sour in no time.

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Dave Carpenter is editor-in-chief of Zymurgy and author of The Illustrated Guide to Homebrewing. He is an avid homebrewer, an inquisitive traveler, and, despite his surname, an ineffectual woodworker. Dave lives in Fort Collins, Colorado, with his wife, two cats, and countless unfinished projects.

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