Commonly known as sour beers, there are numerous variations and interpretations of what goes into the brew that ranges from fetching to funky

Story & graphics by Neill Pieper

Enter most breweries these days and take a gander at the beer list. You’ll typically see the usual IPA, pale ale, lager, hefeweizen and amber. But what about a Berliner Weisse? Or a mixed-fermentation sour? Or maybe even a gose?

More likely than not, you’ll run into one of these beers on your path to finding the newest brews and logging them into Untappd, that neat little app that helps you track the beers you’ve tried.

The sour craze that has enveloped the craft beer community is spreading, and first-time sour drinkers are offered an astounding array of flavors that range from slightly tart to stinging heart-burn inducers.

The unique flavor profiles of this broadening segment of beer leaves room for a lot of discussion.

Alan Simons, head brewer at Dry Dock Brewing Co., said he and other brewers face a similar problem when trying to introduce sours to their patrons: What’s in these sour beers? Where did they come from? An industry-leading book can help explain it.

“American craft brewers have built their industry by combining and adapting brewing techniques and recipes from all over the world,” Michael Tonsmeire wrote in his book “American Sour Beers.”

The same can be said for sours. Breweries here in the States are adapting lambic styles from Belgium, gose and Berliner-weisse styles from Germany, among others. These “sours” involve a bit more science than your typical ale.

What is a sour?

Sour is a blanket term used for beers brewed with bacteria and unusual yeasts.

Sour often refers to beers that have enough lactic or acetic acid to create varying degrees of tartness. These acids come from intentionally infecting beers during different times of the brewing process with known strains of bacteria (lactobacillus, pediococcus and acetobacter — see the tree at right). Though they sound unusual, they are commonly found in yogurt, in the air or on fruit.

In addition to bacteria, yeast is an important part of a sour beer’s makeup. Although it has no souring properties, unique yeast strains provide funky, fruity flavors and aromas.

How are the bacteria introduced?

Yeast and bacteria can be added in three ways: intentionally by kettle souring, during fermentation, or spontaneously through open-air fermentation.

The spontaneous approach involves leaving the beer, typically in the wort stage, open and exposed to airborne wild yeasts and bacteria.

“Brewing a lambic relies on spontaneous fermentation with wild microbes, predating the study of microbiology and making it more art than science,” Tonsmeire said.

On the other hand, bacteria and yeast are intentionally added during the kettle souring brew process. It’s then boiled away before fermentation.

Wood and steel souring occurs during fermentation, in either wood barrels or steel tanks. (See diagram below).

How should one taste a sour?

Simons from Dry Dock offers the three-sip rule for tasting sours.

1. Shock: The first sip is the harshest, overwhelming the palate.

2. Calibration: By the second sip, you have acquainted yourself with the intense flavor.

3. Distinction: Third time’s the charm. You begin to pick up on the nuances prevalent in the beer. Find the different flavors of the beer coming together and decide what you like, and what you don’t.

Who should drink sour beer?

Trick question. Everyone. Whether you think you like sours or not, part of drinking beer is experimentation, from that first sip of your dad’s Rolling Rock to your 50th Fat Tire. Recently converted wine drinkers are often attracted to sours because of the similarities of taste. Techniques used in sour beers are similar to that of vinification (wine making) and sours are often aged in wine barrels, imparting grape and oak flavors.

Want to know more? Ask questions. The fine folks behind the bar at most craft breweries are happy to advise and educate you on what’s in their sour.

Neill Pieper uses his considerable thirst for the craft beer scene to provide editorial, marketing and online production at Thirst Colorado.