If you’re at all involved in the craft beer scene, you may have noticed the growing popularity of sour beers. Personally, this variation of brewing served as an entry point to foster my own love for beer, and beer-lovers and non-beer-lovers alike seem to have an affinity for the tart tang of these brews.
So what makes a sour beer sour? Standard beers are typically fermented with the Saccharomyces strain of yeast. This yeast eats the sugars in the brew to create the alcohol, and it yields reliable, consistent results for an easily replicated beer — the prime goal for most breweries.
Once you get into sours though, all bets are off — a sour beer introduces a strain of wild yeast and/or bacteria in the second round of fermenting. Most commonly, Brettanomyces (Brett) yeast, Lactobacillus or Pediococcus bacteria are used. Brett lends itself to earthier flavors, (think mushroomy-potatoey notes), while both of said bacterias produce Lactic Acid, which accounts for the tanginess comparable to plain yogurt. A myriad of other bacteria and yeasts can be used and combined, which leads to incredibly complex — and often unpredictable — flavors. Throw in the optional addition of fruit into the mix, and you’ve got a brewing party unlike any other. Especially because this party is hard to control — many breweries will stray away from sours because the wild yeast and bacteria used can easily find their way into other brews, upsetting the expected results and “contaminating” the equipment.
While most people associate sour beers with a modern new trend, it’s actually some of the oldest beer around. Most popular in Germany and Belgium, sour beers were extremely prevalent because it wasn’t possible to isolate specific yeast strains (or properly sterilize the equipment, I’d assume). The most traditional style of sour is the Belgian lambic. To create these sours, the Belgians utilized spontaneous fermentation. That means that the brew was exposed to the air, and naturally occurring yeasts and bacteria could find their way into the beverage. Traditionally these bacteria and yeasts came from the aging wooden ceilings in the cellars. Then, for the secondary fermentation, the brew was stored in scrubbed former wine barrels to age and develop a complexity of flavor. A mixture of an older and newer lambic is called a Geuze.
Another subset of sour is the Gose. Gose’s are very tart and brewed with notes of coriander and salt. One of my favorite Goses is Dogfish Head’s SeaQuench Ale, a Gose brewed with plenty of lime that tastes like the sour beer equivalent of a margarita.
Berliner Weisses are sour German wheat beers and are a bit more approachable to newbies because their tangy flavor is less intense and smoother when paired with the wheat. I’d recommend Berliner Weisses and fruit sours to those just beginning to experiment with the genre. Funkwerks here in Fort Collins produces a variety of fruit sours, their most popular being the Raspberry Provincial, which I highly recommend.
As the sour beer scene develops more and more, the different subsets are sure to expand, so just keep tasting to find what you like! No sour beer will be the same.