Some magnet board wisdom at our taproom, Mousetrap.

Why Wild Does Not Mean Sour

How did “sour” a flavor profile, come to be an umbrella term for “Wild,” a style of beer that uses wild yeast? Wild fermentation is the oldest way to make beer, but wild ales are currently one of the least understood and most poorly defined styles, which creates a lot of confusion when it comes to the relationship between sour and wild. Let’s start with a simple truth — wild does not mean sour. What does wild mean then?

At one point, all beer was wild, relying on native sourcing to provide yeast to ferment. As we gained more of an understanding of what was happening and that fermentation was not, in fact, magic, we were able to start reusing yeast from batch to batch. When batches fermented poorly or unpredictably that yeast was abandoned and when it performed well it was kept and repitched. For generations, brewers have used and re-used these same yeasts over and over, all the while putting selective pressure on them to perform the way we want and nipping any aberrant mutations in the bud. Inventions such as the microscope and sterile technique helped accelerate and codify this. During this process we ended up with pure strain cultures of both lager yeast (Saccharomyces pastorianus) and a plethora of ale yeasts (Saccharomyces cerevisiae). Modern techniques such as PCR (Polymerase chain reaction) and genomic sequencing are helping us further understand and categorize these yeasts. All this development is fantastic — we have a well made toolkit and a thorough knowledge of how to use them. But along the way, we’ve lost something. Not only have we lost countless yeasts and yeast mutations that were discarded along the way because they didn’t fit with whatever the predominant goal of the times and region were, but we’ve also begun to lose that elusive sense of wonder. Super-expressive saison yeasts that ferment super hot? Not sure how you got here, but we’re trying to make lager beer in caves in Bavaria so out the window you go.

Five Italian Barolo foedres, and one French Calvados foedre. These serve as both an aging vessel as well as a source of wild yeast.

Wild brewing seeks to bring us back around to some of this unexplored territory. By capturing non-domesticated yeasts as they float through the air or from sources such as old wine barrels or fruit skins, brewers were able to find novel yeasts and, with them, novel flavors. Stewed jam, blueberry juice, bright lilac, and musty leather. The possibilities are endless, but are all flavors that would have been roundly rejected in the race to industrialized beer. Post- Budweiser, though, there’s a host of us that are more interested in these beers and the sense of exploration involved in creating them. These wild yeasts don’t always work well or as expected, of course. Sometimes they create undesirable flavors and we discard them. Sometimes they create pleasant flavors but don’t ferment a beer to completion or the flavor profile is out of balance and needs a little something. In these cases, we’ll blend in other yeasts and bacteria to make up for these deficiencies in the fermentation profile. A practice known as mixed culture fermentation.

There’s a lot of science and discipline that goes into breaking the rules.

All yeasts used in brewing create a level of acidity. A typical wort is cast in the range of 5.2–5.5 pH. Through the process of breaking down sugar into alcohol and CO2, acidity is created and the pH drops to around 4.2–4.4. Some yeasts will push it a bit lower through the creation of additional organic acids, but ultimately yeasts (wild or domesticated) that create what we would think of as “tart” are relatively rare. Most of the acidity in beers that have “perceived acidity” or sour character are derived from bacteria. Of these beers with perceived acidity, a few categories have emerged that are primarily based on production method.

The quickest and least costly method is to perform a lactobacillus fermentation prior to the addition of brewing yeast. This can be done either in a controlled, anaerobic environment of a stainless steel tank (such as we do with Fierce and Troublesome for example) or through the sometimes derogatory practice known as “kettle souring.” A lot of the negative stereotypes of kettle souring have to do with the creation of poor quality, off flavored beer which result from brewers inability to carefully control the fermentation in a vessel not designed or really fit for controlling and restricting contaminates and oxygen ingress. The other issue is that some breweries take advantage of the idea that all beer with perceived acidity are being referred to as “sours” and then grossly overcharge for those beers even though they can be made in the same time-frame as a standard ale with a negligible increase in fixed labor and ingredient cost.

A second, much more difficult and costly method to create a beer with sour qualities is through the introduction of mixed cultures utilizing Brettanomyces and Saccharomyces yeasts in addition to lactic acid producing bacteria such as Lactobacillus, Peddiococcus, and others. These are generally fermented and aged for a significantly longer time than standard ales, often in wood vessels, and require a much higher level of skill and specialized expertise to balance the multivariate needs and fermentation time-frames required by each of the different organisms that need to work in concert. All of these elements add substantial costs, of course, but, in our opinion, are well worth it.

Checking in on one of the foedres.

Whether these yeasts and bacteria are pure culture, domesticated strains, or are wild caught organisms is a further classification. There’s certainly nothing wrong with ordering pure culture, well understood cultures from a yeast lab; however, we personally feel that pushing the boundaries, searching out and befriending new, interesting wild yeasts and bacteria is an inherently more interesting, substantially different process. The nature of this classification is similar to the differences between farm raised vs wild caught salmon or factory eggs vs cage free eggs. In its simplest form, the base is the same, but the level of complexity and detail is substantively different and we think beer is one of those things where detail matters.

Some of the beers produced with wild and/or mixed culture have acidity and in some of these beers, acidity is the star of the show; however it is rarely the only characteristic present and needs to be balanced and congruent with all the other qualities. Regardless of how much acidity is present, “wild” necessarily refers to the sourcing of the organisms involved, not the flavors they create. A general lumping off all these beers as “Sours” has led to several problems in the industry. Obfuscating production methodology has lead to artificially inflated pricing. The nomenclature results in prizing acidity above balance and harmony. Even in the flawed name, different acids and levels of acidity taste radically different! Lactic and citric acid are bright and spritzy. Malic and tannic acids are much deeper and add structure and tone. Acetic acid is vinegar and both gross and a sign of poor practice outside a few, very specific styles.

So now that we know what wild means, how can we effectively introduce this information to beer drinks? This discussion has directly influenced our decision to present many Off Color beers in a new way that should better inform our customers. In order to best convey the processes involved and flavors one can expect in our beers, we’ve started adding emblems to many packaged offerings. Read more about the new emblems here.