If 10 years ago you had offered someone a beer that was sour, you might have been given a sideways look. Sour meant something was wrong. It certainly wasn’t what beer was intended to be.

But times have changed. Sour beers are in demand. Flavors once limited to obscure brews from Belgium have been embraced by brewers across the United States. American wild ale is a recognized style category. And American beer drinkers are lining up for a taste.

Just what is a sour beer? I put that question to Niko Tonks, head brewer at Fair State Brewing Cooperative, one of the top wild-ale brewers in the Twin Cities.

“The simple, pedantic approach is to say that sour beer is beer that is sour,” he said. But the category encompasses a wide range of flavors, from lemony tartness to rustic leather and barnyard funk. “So the more complex answer is that sour beers are beers that employ yeast and bacteria to produce alcohol and lactic acid.”

It may not sound appealing, but it’s true. Fermentation with wild yeast strains like Brettanomyces — the winemaker’s enemy — and bacteria such as Lactobacillus is what gives these wild brews their funky flavor.

Brewers introduce these bugs in a variety of ways. Lab-cultured, pure strains can be added to the beer just like normal brewing yeast. Fresh wort can be left to sit for a period of time before boiling to allow lactobacillus from the surface of the malt to partially ferment its sugars, producing acid. Aging in wooden barrels, where the various organisms have taken up residence in the porous wood, is another method frequently employed.

Fair State Co-operative's Roselle is a good introduction to sour beers.

A change of taste

The Twin Cities has long been known as a hop-centric market where pale ale and IPA are king. But drinkers here have taken a liking to the sour beers. And local brewers are obliging.

“I think the reason it’s caught fire here is that we have a big beer-enthusiast community,” said Tonks. “People are looking for it. They are doing trades with people on the internet for beers from the coasts. There was a call for it here locally. The simple answer is that people wanted it and so it’s happening.”

Fair State Brewing Cooperative has one of the more robust sour beer programs locally. It makes up 25 to 30 percent of their monthly output. Their popular LÄCTOBÄC series sees a revolving assortment of wild-fermented ales that are available at the northeast Minneapolis taproom and select bars. It’s worth a stop to see what’s brewing.

Fair State also offers a number of sours in cans and limited-edition bottles. Roselle — available in cans — is a great introduction to sour beers. The acidity is mild, giving a lightly tart, lemony complement to the base of bready wheat malt. The real driver is hibiscus that brings pleasant citrus and floral notes that linger into the dry finish.

Fans of cold-climate wines will appreciate Frontenac, a sour beer aged in Frontenac and Marquette wine barrels from Parley Lake Winery in Waconia. This is a tart one, with high levels of lemony lactic acid. The barrel character comes through as vinous notes with roselike floral overtones. A touch of leather and barnyard keeps it grounded. Frontenac is a collaboration project with Fulton Beer and Oakhold, a soon-to-be brewery that will specialize in wild fermented ales.

The bottled Lichtenhainer follows a current trend in brewing to revive near-extinct beer styles. This old, German wheat beer style brings together sour and smoke in an unlikely yet delicious partnership. All things are in balance in this complex beer. Bready wheat and tart lactic acid work in harmony, neither letting the other take control. Subtle campfire smoke brings depth while boosting the wheat slightly and toning down the tart. Background notes of green apple complete the picture.

A German variety

Jace Marti of August Schell Brewing Co. is leading one of the state’s most interesting sour beer programs. His Noble Star Series consists of innovative interpretations of another endangered German beer style — Berliner Weisse — that are aged in 80-year-old cypress wood tanks once used to brew Schell’s iconic Deer Brand Lager.

Two new releases on the series are due on shelves in the next month. Music of the Spheres is aged on gooseberries. The acidity is relatively low in this one, letting the green-grape character of the berries shine through. It’s a wheaty, fruity, Champagne-like treat.

Tidal Disruption was aged on blackberries. This dark purple beer is topped by a full head of creamy, pink foam. Acidity is high, giving a puckering sourness that lingers well into the finish. As the beer warms up, the sour is joined by resplendent, juicy blackberry that adds just a touch of balancing sweetness.

Indeed Brewing Co.’s Wooden Soul series features one-off, barrel-aged sours released at irregular intervals. Release is irregular because it’s each beer’s development that determines its readiness. Some take a couple of months, others might take a couple of years. That’s the nature of working with wild critters.

Wooden Soul beers can be found on tap at area bars like the Happy Gnome and the Bulldog in Lowertown. They can also be had at the Indeed taproom.

If you want to take some home, Heliotropic is available in bottles. This is a Belgian-style saison, re-fermented in white wine barrels with two strains of Brettanomyces yeast. Black pepper spiciness leads the way with a fruity background of pineapple, orange and lemon. Sourness is modest and barrel aging imparts a low vinous quality.

For other good Minnesota-made sour beers look for the Funked Up series of beers from Bent Brewstillery. Pentagram is a seasonal sour from Surly Brewing that is available in bottles. Other small-batch, draft sours are often available at the Minneapolis brewery.

Michael Agnew is a certified cicerone (beer-world version of sommelier) and owner of A Perfect Pint. He conducts private and corporate beer tasting events in the Twin Cities, and can be reached at michael@aperfectpint.net.