How Kettle Souring Is Making Sour Beer Cheap and Affordable

A recent seminar held at the 2015 Craft Brewers Conference was a packed house, with brewers from across the world asking questions from three local brewers who have helped establish how to kettle sour: Gigantic Brewing’s Ben Love, The Commons Brewery’s Sean Burke, and Breakside Brewery’s Ben Edmunds. Leading off the discussion was Ben Edmunds, who has helped establish one of the more technical and precise methods of kettle souring, though the methods are so new there is no definitive research or studies established yet. All that it takes to accomplish a successful kettle sour is a kettle with some temperature control and a pitch of Lactobacillus bacteria, either from a yeast laboratory like Wyeast or White Labs or even from a common container of yogurt (Greek yogurt may be best). Lacto is impeded by alcohol and high hop content, so inoculating in the kettle before either is present is a logical evolution.

A similar technique to kettle souring called sour mashing has been around for a significantly longer amount of time. This method is similar in that it relies on lactobacillus to do its work early on before the beer has been fermented or even boiled. However, sour mashing depends on the natural amount of Lactobacillus found on malted grains by adding warm water and beginning the mash as would be done for any other brew, but instead just leaving the grains to steep in water over night. Brewers come in the next day and then continue brewing as normal, often only mashing smaller percentages of the total grain, say 20% a day ahead. Soaking the malt in warm water will activate the Lactobacillus and it will begin to develop acidity and tartness. However, there are significant downsides to this method and results can be varied. “The results can be good, but they also be very very bad (butyric – baby sick, caprylic – goaty/waxy, more…),” says Ben Love, and Sean Burke noted in his CBC seminar, “Lacto does grow on malt, but so do a lot of other things…”

The Commons’ Sean Burke

Practice and Method for Brewers

Ben Edmunds recommends doing a kettle CIP before beginning a kettle sour. If you’re a pro brewer or homebrewer with a heat exchanger or wort chiller, you may want to CIP or pasteurize that ahead of time as well. When kettle souring, you begin your brewing process as normal, mixing your milled grains with hot water and mashing in. The regular steps continue as usual until you transfer your hot wort into the boil kettle, separating it from the mash. At this point you cool and recirculate the wort in the kettle and pitch lactobacillus once the wort gets down to the 115-110 degree range. Wyeast Laboratories 5335 Lacto is a recommended variety available to both home and pro-brewers.

Both Ben Edmunds and Sean Burke recommend first bringing the wort up to a boil for 5 minutes before running through a heat exchanger to cut down on DMS (an off flavor) and lowering temperature in a whirlpool. You need as little as 5 gallons of lacto for every 4 barrels of wort (or about 4% of your total volume), with often an even more drastic drop in pH with lower pitches. Fresh lacto not stored for long periods is recommended. The most important part outside of having a healthy amount of Lactobacillus to pitch is the ability to hold the temperature of the wort between 108 and 115 degrees for up to 48 hours after the lacto has been added. This warm, sugar rich and hop and alcohol-less condition is ideal for lacto to work its magic, dropping the pH drastically in the first 18 to 24 hours. This is a good time to blanket your wort with gas at 2 PSI while waiting. Depending on the acidity level you are going for and whether you will be blending sour beer with non-sour, you will want to hold it for up to 2 days before finishing the kettle souring process. All three brewers on the panel agreed that kettle souring does produce a quick but one-dimensional sour product, though there is some disagreement with how much soured beer to use. Ben Edmunds at Breakside believes in blending kettle soured beer into non-soured beer with fruited beer or barrel-aged beer. Gigantic Brewing has always used 100% kettle soured wort for its beers, but does believe in brewing in conjunction with other unique ingredients like fruit, hops, or herbs and spices to add flavor around the acidity. Ben Edmunds looks for a drop to 3.4 pH after 24 hours and then cutting off the souring process. All brewers recommend cutting off the kettle souring between 3.4 and 4 pH. To finish the kettle souring process you now must simply bring the wort up to a full boil and continue brewing as usual, adding hops or any other special ingredients and then cooling and fermenting with a regular ale or lager yeast as usual. Doing a full boil is key here because it kills all of the Lactobacillus, thus stopping the pH drop and sanitizing your kettle of bacteria.

Advanced techniques for kettle souring to avoid some of the pitfalls are using small percentages of acidulated malt to drop the pH more quickly, thus protecting the unfermented wort from interio-bacter growth that could cause off flavors. Breakside notes a strange peanut shell/nutty character coming from kettle soured beers that use darker crystal malts. Sean Burke recommends keeping your bittering hop addition for the post boil low due to a clashing character, but bringing dry hopping up for flavor and aroma. A common complaint of kettle soured beers is poor head retention and thin mouth feel, and if that is a concern, you can try using Cara-Hell malt and torrefied wheat or other adjuncts to counteract it.

Kettle Souring with Yogurt

Sean Burke at The Commons was the first that we know of to use the yogurt method of souring for his brewery’s Biere Royale, a popular entry into the Portland Fruit Beer Festival in 2013. Being the first to this unique method has brought Sean and The Commons some buzz, as well as comments that people can taste the yogurt (extremely unlikely) and trying themselves, both professionally and on a homebrew level. This technique is quite easily done by any brewer, including homebrewers. Greek yogurt or any pro-biotic yogurt gets its classic tanginess from Lactobacillus bacteria, the primary souring agent (contrary to many people’s belief that brettanamyoces is responsible). Sean developed this method by simply realizing that “there were certain lactobacillus still viable in live culture yogurt that could potentially sour wort sugars.” He used Greek yogurt, and since then it’s become standard, though there isn’t a lot of basis for it being better than any others. Gigantic Brewing’s Ben Love uses Nancy’s nonfat plain pro-biotic Greek yogurt specifically for its blend of lacto that produces a clean, tart sourness. The Commons uses both a house Lacto culture and sometimes yogurt that has been cultured up by simply stirring into a small batch of wort to get the lacto working and active. “I frankly think the yogurt thing is getting a bit overblown. We tried it on two different beers and it worked for what we needed it to do. It’s not the only way we kettle sour beer, it just unique, so I think people glean on to that.” That said, I think the affordability and ease is a realistic attraction to using yogurt other than the unique concept.

Cantillon filling open fermentation Coelschip

Limitations

Kettle souring is being used at breweries all over the country, from Anderson Valley to Victory Brewing to Boulevard Brewing, usually on Berliner-Weisse or Gose styles of beer. I wondered why kettle souring seemed to be limited to these two narrow styles and no others. “I think that beers that use kettle souring don’t really fall into any classic style. If style means anything from an historical point of view, there are no classic sour styles where kettle souring would be appropriate; Berliner Weisse and Gose might be the exceptions,” said Ben Edmunds. Brewers seem to universally agree that kettle souring is a tool in an arsenal or a piece of a puzzle, but not best used as the final product. Other wild beer styles like Flanders Red or Brown require a more complex fermentation process not achieved in a kettle souring. Sean Burke says, “The complexity of different organic acids and other microbial by-products created through long term, mix culture fermentation can never be achieved through quick turn around kettle or even mash soured beers.” Some recent examples of great kettle soured beers include Breakside’s Bellweather, which uses only 20% kettle soured beer and is layered into gin barrel-aging and kaffir lime leaf . The Commons Myrtle is flavored with Meridian hops, and Sean Burke says, “these beers have benefited from flavor additions such as fruit or citrus zest.” Gigantic Brewing has made a series of fruited Berliner-Weisses, like the upcoming passionfruit flavor for the Portland Fruit Beer Festival. Fruit is recommended to be added after the primary fermentation is finished. And Ben Love says, “Pitching yeast and bacteria and waiting will typically take at minimum 4-8 weeks, or much longer. There is a time and place for beers like that, and we have beers like that going in barrels at Gigantic. Those beers are a different creature than kettle sour beers.”

Sour Beer for All!

With kettle souring there is only one major cost consideration above and beyond the price of brewing other beers, and that is the time consideration of tying up your brew kettle. Purchasing fresh or new strains of lacto could also be a concern, but with kettle souring or storing sour wort for blending, this isn’t a big issue. The time it takes to sour the wort can also be cut down by using methods to rapidly drop your pH over one night rather than two or simply brewing on a Friday and taking the weekend off. The consistent results from kettle souring also cannot be dismissed, while using mixed cultures of yeast or mash souring can produce varied funky results the process of kettle souring is consistent and clean.

Breakside Brewery has been one of the top Oregon breweries producing partially kettle soured beer and packaging it for very affordable prices. Last summer’s hit Passionfruit Sour was followed up with La Tormenta, a dry-hopped sour that did well even with a strange wintertime release; both sold for between $5-$7 for a 22oz bottle. Ben Edmunds estimates Breakside will produce about 1,000 barrels of beer this year that use some portion of kettle soured beer. He says, “ kettle souring has the ability to reduce the time that someone needs to make a high acid beer. Whether that makes it easier and/or more affordable, that depends on the brewery who is making it,” but continues on to say, “I don’t think it’s appropriate to charge the same for a kettle soured Berliner weisse as beers that require years to sour in barrels.” As Ben Love says about the cost of making kettle soured beer vs. brettanamyoces and mixed fermentation sours, “it’s very inexpensive compared with the lab pitches, which you need to propagate. It takes 48oz of yogurt for 20bbl of wort.” With the increased amount of kettle soured beers and their more mainstream availability in grocery stores, we may finally see sour flavored beers go mainstream.

Next week look for a follow-up story on the lasting resurgence of Gose and how its popularity is increasing due to the kettle souring methods outlined in this article.