Sour Beer: A Primer

Beau’s takes a look at the rise in popularity of sour beers, featuring Halcyon Barrel House brewmaster, Bryce McBain, and The Mad Fermentationist, Michael Tonsmeire.

words: patrick jodoin | photos: marc doucette

If you run in craft beer circles you’ve definitely heard the term “sour beer” thrown around. You may be a big fan, or you may be a little reluctant to get into it.

But if you’re unsure about sour beers, funky beers, mixed fermentation, brettanomyces, barrel aging and so on, this article should work as a bit of a primer.

Halcyon brewmaster Bryce McBain

What is sour beer?

Allow the man who literally wrote the book on it, the author of American Sour Beers, Michael Tonsmeire a.k.a. The Mad Fermentationist, to sum it up: “Sour beer really has just become an all-encompassing term for beers that are acidic, tart, and lively,” he says. “Sour beer can be something that’s very simple. It can be something that is crisp and refreshing just like a glass of lemonade in the summer, but it can also be something that is more targeted to a connoisseur … something you want to sip, think about, and enjoy as it either ages or as the beer warms up.”

So how does a sour beer get its taste? And what’s the big difference between it and other beer? Traditionally there is a whole range of intermingling flavours in beer styles classified as “sour,” but simply put, the sour (or acidic) flavour comes from lactic acid, which is produced by lactic acid bacteria, lactobacillus or pediococcus, during the fermentation process in brewing.

These bacteria create acidic flavour. The alcohol is from fermentation by saccharomyces and/or brettanomyces (Brett) or both (mixed fermentation). The creation of alcohol through fermentation is pretty much the same in sour and non-sour brewing. Brett can be used on its own to ferment beer or can be used in conjunction with other microbes. Pediococcus doesn’t create alcohol, although some strains of lactobacillus can.

While wild yeasts like brettanomyces can produce some acetic acid, their main contribution to beer is fruity and funky flavours and aromas. Since brett (a yeast, not a bacteria) is present in many sour beers, it can sometimes be mistaken as the souring agent. It’s not.

Michael Tonsmeire, photo by Cristiano Estrela for Diário Catarinense, Brazil

So what about ‘funk’?

“It’s not necessarily the most appealing word in the English language,” says Tonsmeire, who is also the co-founder of Columbia, MD’s Sapwood Cellars. “It’s not something that I think most people would associate with a positive description of food or most other beverages. I usually like to think of funk as a flavour that in a small amount might be beneficial but too much would be offensive.”

When discussing the taste of funky beers, Tonsmeire often likes to draw comparisons from the culinary world. In the case of ‘funk’ he cites the example of fish sauce with pad Thai: Most people wouldn’t want an abundance of the stuff, but many enjoy a small amount to complement the dish. He believes these beers have the depth and complexity that includes a touch of something curious. The best example of one of these descriptions is the common beer term “horse blanket.”  

Another element worth exploring a little is barrel aging. The processes at Halcyon Barrel House are a good case study: “What I use barrels for is a home for the microbes,” says Halcyon brewmaster Bryce McBain. “I’m not looking to get a lot of wood character — I’m ok with some tannins to help build the body of the beer — but mainly it’s a place for the bacteria and wild yeast to live. Wood is porous. Bacteria and wild yeast can get right in there. And then even if you clean that barrel out they’re still going to be in the wood so the next beer you put in there will carry that microflora forward.”

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While sour beers are undoubtedly currently enjoying an upward trajectory, they’ve been around as long as beer itself, so to call them a trend is unfair. “Before the isolation of brewer’s yeast, all beer had more than one microbe in it,” says McBain, who specializes in mixed fermentation in barrels, creating some seriously funky and sour beers. (To find out about the standardization of brewer’s yeast, check out the blog post ‘Brewer’s Yeast: The employee that works 24 hours a day.’)

Curse of Knowledge is a barrel-fermented, barrel-aged blended farmhouse saison with brett. Spice and more delicate herbal, fruity and floral elements are rounded by its relationship with wine.

How did sour beer get to where it is today?

“I think we wouldn’t have sour beer the way it is without Belgium,” says Tonsmeire. “There are Belgian examples that certainly were the spark that kept sour beer — good, really interesting sour beers — alive. If World War 2 had put every one of them out of business and none of them had recovered I imagine that sour beer would be very different in [North] America — I’m sure it would be decades behind.”

“These are the sort of beers you can’t bootstrap,” he adds.

Tonsmeire cites Cantillon, and the lambic breweries, as the keepers of the microbes necessary in sour beer brewing. He says the firsthand experience of American brewers who have gone to Belgium to work or intern for a few months, collaborations with Belgian brewers, and Belgian beer writers are what has helped bring sour beer to North America. Peter Bouckaert, the former brewmaster at New Belgium, was also instrumental in the spreading of Belgian beer styles, and sour beers, to the United States. In fact, Bouckaert and New Belgium were investing in foeders when sour beer was not a hot topic or something people were excited about.

“I think everyone has a personal journey into sour beer that is often based on what they have access to, or what they’ve tried,” says Tonsmeire. “It was 13 or 14 years ago that I started drinking beer with any sort of intention. There were probably only 15 or 20 places in America that had brewed any sour beer, and now it’s pretty rare to find a brewer who has never brewed a sour beer of any sort at any time, and more and more are doing it seriously.”

McBain tells a similar story, having discovered Rodenbach Grand Cru at 19, beginning a love affair with Belgian beers that later informed his life as a brewer.

Sour beer is currently popular in the United States and Canada, according to both Tonsmeire and McBain, because of the overall popularity of craft beer in general. Sour beer, in particular, is often a labour of love, as it requires great patience.

“Devotion to sour beers pays dividends,” says Tonsmeire. “That’s hopefully how they survive.” Brewing sour beer is very tricky to do alongside brewing beer with saccharomyces, as the risk for contamination of brewing systems from the introduction of lactic acid bacteria and brettanomyces is great.

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What’s the big takeaway for craft beer fans today who are looking to begin their own journey with sour beer? Just let your palate adjust to the acidity, and get out there and sample as many as you can.

“The biggest tip is that sour beer has such a big range — keep trying it,” says Tonsmeire. “Just like non-sour beer there are dark ones, light ones, citrusy ones, and roasty ones. It’s a whole other category and to just try one or two sour beers you may not find the sour beer that is to your palate, to your taste.”