Most beer drinkers are familiar with styles like Amber Ale, IPA, Pilsner, and Stout. These would be what we refer to as “clean” beer styles. And that is because of one ingredient – yeast! Clean beers use yeast that act a certain way and produce a specific set of flavors. Wild beers, on the other hand, use very different yeast along with a variety of other microorganisms to create beers that are exceptionally complex. Wild ales such as Lambics, Flanders ales, and Farmhouse ales are often described as funky, sour, or tart.
Before we get into the differences between these beers and their yeasts, we should talk about the role yeast typically plays in making beer and what yeast is. The type of yeast used in fermentation comes from a family of fungus known as saccharomyces. These fungi are single cell organisms used in brewing, baking, and winemaking.
The most common type of yeast used throughout brewing history is saccharomyces cerevisiae and is often referred to as ale yeast or brewers’ yeast. Saccharomyces loosely translates to ‘sugar fungus’ and cerevisiae is Latin for ‘of beer.’ So ale yeast is sugar fungus of beer. It is believed that this yeast strain was originally isolated from the skins of grapes. Another yeast commonly used in brewing is saccharomyces pastorianus, and is also known as lager yeast. It is a hybrid closely related to s. Cerevisiae but not unique enough to be its own species.
The main role of yeast is to produce alcohol, which happens when the yeast consume sugar and reproduce through a process known as budding. During this process, the yeast cells create ethanol, CO2, and aromatic compounds as byproducts of their reproduction. This process is known as fermentation and is the single most important stage of brewing beer. In essence, this is where our concoction of ingredients – water, hops, malt, spices, fruit, whatever – transforms into an entirely new product with new tastes and aromas that weren’t present before. This is also where the beverage becomes alcoholic.
Because fermentation is so important to the brewing process, changes to the process or to the yeast, wink wink, can have major influence on a beer. And this brings us, finally, to wild beer. While most of the beers we drink are fermented using either saccharomyces cerevisiae (ale yeast) or saccharomyces pastorianus (lager yeast), wild ales incorporate another type of yeast known as brettanomyces or brett for short. Brett is what produces the funky flavors associated with beer styles like Lambic, Saison, or Oud Bruin.
Brewer’s yeast likes to eat a variety of simple sugars, including sucrose, glucose, and fructose. Brewer’s yeast especially likes to eat malt sugars – maltose and maltotriose. On the other hand, brettanomyces likes to eat everything. Brett will consume all the same sugars saccharomyces will but will also consume long chain carbohydrates, which brewer’s yeast is unable to consume. Brett also works at a much slower pace than brewer’s yeast. In the wild, Brett can be found on the skin of fruits.
While brett brings the funk, the sourness in wild ales comes from a number of bacteria, with Lactobacillus and Pediococcus being the two most common types used in creating sour beer. And like yeast they also go through a reproductive process but instead of ethanol their main byproduct is lactic acid. The presence of lactic acid creates an acidic or sour taste in the beer. These types of bacteria are commonly referred to as lactic acid producing bacteria or LAB for short.
Wild ales will use saccharomyces, brettanomyces, lactobacillus, and/or pediococcus to create beers with complex, funky flavors that are often described as hay-like, barnyard, musty, and other words that aren’t commonly associated with beer.
The most commonly known example of a wild ale is Lambic. We have written documentation of lambics dating back to 1320, making it the oldest surviving style of beer in the world. Lambic is only produced in one place, the area in and around Brussels, Belgium, known as the Senne River valley. The special blend of microbes naturally present in this region is key to the unique flavors of Lambics.
These special beers are produced using a process known as spontaneous fermentation, where the unfermented wort is exposed to the air at near boiling temperatures and allowed to cool overnight. While the wort cools, microbes such as brewer’s yeast, brettanomyces, and lactic acid bacteria make their way into the liquid. The liquid is then transferred to wood barrels where the wild microbes begin their extremely long fermentation process. Most lambics are left to ferment for at least one year before packaged or blended with other Lambics of different ages to create a style known as gueuze. Sometimes Lambics are refemented on fresh fruit creating other well known styles such as Kriek (cherries) or Framboise (raspberries).
Although wild ales may have originated from Belgium, they are not exclusively made there nowadays. Brewers from around the world have been inspired by the brewers of Belgium and wild ales have become increasingly popular in America as craft brewers have adapted the old world techniques of Europe into their own versions of American wild ale. Breweries like Hill Farmstead, Russian River, Allagash, The Lost Abbey, Strange Roots, Crooked Stave, and Jester King are just a few of the breweries with large portfolios of wild beer.
For more information on American Wild Ales and how wild ale is made in general, I highly recommend the book American Sour Beers by the great Michael Tonsmiere. If you’re interested in learning more about yeast and its role in brewing, check out Yeast: The Practical Guide to Beer Fermentation by Jamil Zainesheff and Chris White. Finally if you’d like to learn more about the wild beers of Belgium that inspired millions around the world, I recommend picking up either Wild Brews by Jeff Sparrow or Great Beers of Belgium by Michael Jackson.