Sour beer: A term many American beer drinkers used to negatively describe beer for decades. Although popular globally for centuries with the likes of Cantillon and Boon, sours have more recently taken flight domestically in popular beer culture, especially with the rise of the kettle sour.

Unlike their traditional brethren, kettle sours (like a gose or berliner weisse) brew faster than the traditional method, appropriately labeled “quick souring.” Not only is a stainless-steel kettle or fermenter used instead of a traditional wooden barrel, but lactic acid bacteria (often times Lactobacillus) is also pitched to achieve the desired PH, and then the wort is taken through a normal fermentation process. These beers are ready for consumption typically in weeks versus the months and sometimes years traditional sours need to fully develop and mature.

The History of Sours

Prior to refrigeration and pasteurization, all beer was essentially sour beer, as naturally occurring bacteria had a presence in the brew for thousands of years. In the late 1800’s, brewer’s yeast was purified and would allow brewers to exclude bacteria, like lactobacillus, that gave off undesirable flavors. Brewers in America utilized this advancement for over a century to make refreshing lagers and ales for the masses.

Many of their European counterparts, however, continued to utilize lactobacillus, brettanomyces, and other wild bacteria as crucial components of complex and enjoyable beers. Aforementioned Cantillon saw this value and has been producing their traditional lambics since the late 17th century. Cantillon, like many others throughout Belgium, uses coolships for an open or wild fermentation, letting air born bacteria work its magic.

The History of the Kettle Sour in the US

We can’t help but notice the upward trend of kettle sours from, often, the same producers crushing Idaho 7 and Citra into juicy hop bombs we so affectionately devour. But what were the factors that contributed to the rise of kettle sours in America?

One thought is that they’re approachable for most consumers. “We design our sours as gateway sours,” says Paul Grenier, Co-Owner and Brewer at Mortalis Brewing Company in Avon, New York. “When we’re working on designing our beers, PH (a measure of the power of acid in the solution) is top of the list. By far one of the most important things for us is introducing people to a PH they can handle and not strip the enamel off their teeth.”

Although only open for a little over 5 months, Mortalis has burst onto the scene making approachable sours like “Medusa,” a berliner style sour with passion and dragon fruit, and “Cerberus,” a sour with raspberries, blackberries, and blueberries mixed with milk sugar and marshmallows. Ingredients like the ones included in Medusa are just one example of how brewers are pushing the limits to what flavors and taste profiles are possible with their sours.

“It’s challenging to separate yourself, but they’re fun to brew,” says Joe Delcalzo and Pete Reuther, owners and brewers of Brix City Brewing, a brewery in Little Ferry, NJ producing well-regarded kettle sours and IPAs. “Breweries that are making good beer will be able to brew them.”

Standing Out

As their popularity continues to grow, brewers have their own opinion on what will make their sours standout. “The key, for us, is avoiding the negative parts of kettle souring by souring our beer anaerobically,” says Jason Synan and his partner Michael Renganeschi from Hudson Valley Brewery. “Oxygen in these kind of fermentations leads to all sort of off flavors, which have come to be the calling card of a bad, cheat code style kettle sour.

“At Hudson Valley, ‘kettle sour’ is a little bit of a misnomer, because we do all of our lacto-fermentation in fully anaerobic conditions in our stainless-steel fermenters.” Paul and his crew at Mortalis believe in knowing your cultures and brewing fundamentals. “Knowing your strain and your culture you’re working with,” says Paul. “We have a lacto strain that we really enjoy. When you’re dealing with this organism, it can grow in strength and expedite a particular sour the stronger it gets over time if you culture it.”

Where is the Kettle Sour Heading?

In a world where we, like the Instagram updates, move at the speed of light, what does the future hold for kettle sours? What about traditional barrel aged sours?

“Although we make kettle sours, we don’t want people to forget about our traditional sours,” says Joe and Pete from Brix City Brewing, “both have their place in the beer scene, as long as people understand the differences between them.”

One thing is certain, the popularity will only challenge brewers to continue to innovate and hone their skills. “It requires extra equipment and extra processes,” says Hudson Valley, “like steam cleaning tanks and lines after souring- to ensure the final product is pasteurized and shelf-stable. Eventually, I think we’ll be talking about acidity the way we do at Hudson Valley: as just one more layer to the complex arrangement of beer.”

3 of the Best Kettle Sours

Volcano Sauce

Aslin Beer Company — Herndon, VA

Sour brewed with blueberries, blackberries, vanilla, and lactose. They describe it as the berry flavored crème brûlée you wish you could get your hands on. We won’t argue.

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Hudson Valley Brewing — Beacon, NY

Sour DIPA with raw wheat, malted oat, milk sugar, dark chocolate, and chamomile. Hopped with Citra and Simcoe powder. The layers and complexity in this beer are unparalleled.

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Double Blush

Mikkeller Brewing SD — San Diego, CA

Imperial berliner weiss brewed with coffee and raspberries. Crazy combination and nuance of flavors that work together. And the double is extra nice, clocking in at 6.5%.

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