For most craft beer drinkers beer is either malty, hoppy, or both and in varying degrees depending on style. Hundreds of pints later the craft beer enthusiast has navigated through many different styles, as well as their sub-categories, learning the subtle nuances of how slightly more roasted grain and shifts in ABV can push a beer into an entirely new style. Just when all of this is starting to make a lot of sense, your friend introduces you to a Geuze, Lambic or Flanders Sour that blows every pre-conceived notion of what you thought beer was. For some, the experience serves to remind them that they never want to drink one of those bitter creations ever again, but for others, it is the first step down a whole new road of discovery.
I have heard brewers say that nearly 70% of what we taste in a beer is attributable to the yeast. There is no denying yeasts role in beer production. Without these unique organisms what we call beer would only be very sweet barley water. The yeast eats all of this sugar and its excrement is CO2 and alcohol - two major contributions to our favorite beverage. In many of the massively hopped or huge barley beers that we encounter on a regular basis, it can be difficult to hand yeast most of the credit for their bold flavors. In the case of sour beers, there is no denying the dominant and indispensable role that yeast plays.
The yeast we are most familiar with in ales is Saccharomyces cerevisiae and in Lagers Saccharomyces pastorianus. Their signature flavors do much to define the specific beer styles that are fermented with the many selected strains of both species. Sour beers involve an entirely different microflora that often comes from the open air. In the case of most sour ales the primary fermentation organism is the wild cousin of Saccharomyces - Brettanomyces. "Brett" lives on fruits and grains as well as in the air and on most surfaces. Before commercial yeast strains had been developed, beer was fermented by these wild strains that floated into the open fermentation vats.
"Brett" fermented beers take on distinctively wild flavors that range from tart citrus to earthy/herbal notes to dominant barnyard flavors. One significant difference between Saccharomyces and Brettanomyces is the fact that Brettanomyces have the ability to eat nearly all of the sugar in the wort, where Ale and Lager strains of Saccharomyces only eat so much sugar and then stop. The absence of sugar is why the Brettanomyces fermented ales are typically super tart.
These sour beers are a bit of an acquired taste and are not for everyone. For many long-time craft beer drinkers they are at the very top of the food chain and I think there are a number of good reasons why. First, it takes a dedicated craft drinker to persist beyond the initial blast of acetic acid to the massive complexity that reveals itself after the taste buds have settled down a bit. Second, after spending years drinking high ABV beers that have big residual sugars there is something quite refreshing about these fully attenuated beers that have only 5ish % alcohol yet drink like something with 12%. Third, if you have ever had one too many sweet beers you will learn the very next morning why they are to be consumed in limited quantities. The sours, however, rarely deliver the characteristic big beer hangover.
Lambics, Sours, and the like offer the craft drinker a whole new frontier to explore and, in my experience, have been an exciting and rewarding departure from the typical craft selection. That's not at all to say that I don't have a soft spot in my heart for the many wonderful craft beers that find their way onto our taps. My hope here is to cast some light on a style that is often overlooked or avoided entirely. The enjoyment of craft beer is a life-long journey of discovery. What makes this journey of discovery so exciting is finding new paths and new inspired products along the way. I trust you will find the sours a road well worth exploring and a style worthy of the most discerning palate.