Born To Be Wild: Brettanomyces-The Wild Yeasts behind Cultured Beers
At BSI, we carry a microorganism that has long captivated the imagination of brewers and beer enthusiasts alike. Its name holds a certain mystery, a whisper of wild aromas and complex flavors: Brettanomyces. Often referred to as “Brett”, this genus of wild yeast has carved a niche for itself in the world of craft beers, elevating brews to new heights of taste and aroma.
In 1904, N. Hjelte Claussen, director of the New Carlsberg Brewery in Copenhagen, isolated and introduced Brettanomyces to the world. Claussen was able to demonstrate that strong English stock beer underwent a slow secondary fermentation. As a result, the secondary fermentation process produced the characteristically high-gravity British beers, and Claussen was able to replicate those by inoculating beer with pure Brettanomyces cultures.
Brettanomyces, derived from the Greek words “brettanē” meaning British and “myces” meaning fungus, is a genus of wild yeast found in the natural environment on surfaces such as the skins of fruit or wood. In contrast to the commonly used brewing yeast Saccharomyces cerevisiae, Brettanomyces is known for its ability to ferment complex sugars and other compounds not accessible to Saccharomyces, leading to a much wider array of distinctive flavors and aromas in beer.
Using Brettanomyces in Brewing:
The use of Brett introduces a unique set of challenges and opportunities in the brewing process. Although historically considered a nuisance due to its unpredictable nature, Brett has been a companion to brewers for centuries. It is tolerant to alcohol as well as many fermentation conditions, and in recent years, craft brewers have embraced its wild character, incorporating it intentionally into their beer recipes.
Strains of Brettanomyces often take months or even years to complete fermentation in comparison to much faster fermenters of Saccharomyces. This prolonged fermentation period allows for the development of complex flavors and aromas, resulting in fruity esters, spicy phenols and earthy, rustic notes in beers. These aromas are often described as funky, barnyard-like, or leathery.
Many brewers employ a technique called mixed fermentation, where both Saccharomyces and Brettanomyces yeasts are used together, along with lactic acid producing bacteria. These combinations result in beers with extraordinary complexity, depth, and most of all, sourness. These are seen in styles like Lambics and American Wild Ales. The flavor characteristics of wild and mixed fermentations can vary widely depending on the strain of Brettanomyces and/or Saccharomyces used, the brewing process, ingredients, and the beer’s aging conditions.
Brettanomyces Strains
Researchers have identified five species based on ribosomal DNA sequence homology:
Brettanomyces bruxellensis, which includes B. intermedia, B. lambicus, and B. custersii
• … anomalus, which includes …claussenii
• …custerianus
• …naardenesis
• …nanu
In truth, there are only a few Brett strains that brewers regularly use and those tend to include bruxellensis, lambicus, and anomalus. B. bruxellensis is a great strain for secondary fermentation. B. lambicus as the name would suggest, is that which is commonly associated with the lambic-style. B. anomalus, a lesser known strain which includes the variation claussenii, produces more fruity flavors.
Brewing Science Institute: Yeast Library
At BSI, our Yeast Library has a variety of wild yeasts to choose from:
• B. bruxellensis – A classic Brettanomyces strain that produces a medium intensity Brett character, with earthy and mild fruit esters. Ideally suited for secondary fermentations in Belgian and lambic-style beers.
• B. bruxellensis var. Drei – A unique and highly aromatic Brettanomyces strain. Produces complex earthy and fruity esters reminiscent of sweet tarts. Fruitier than regular bruxellensis. Ideally suited for secondary fermentations in Belgian and lambic-style beers.
• B. claussenii – A Brettanomyces strain that produces a low intensity Brett character, with subdued fruitiness and a slight earthy profile. Both primary fermentation and secondary fermentation steps use Brett. Ideally suited for secondary fermentations in Belgian and lambic style beers.
• B. lambicus – A Brettanomyces strain that produces a high intensity Brett character. Very funky “horse blanket” aroma and flavor. A classic strain used by a Trappist brewery in the Guame region of Belgium. Ideally suited for secondary fermentations in Belgian and lambic style beers.
“Brett” character can take extensive aging to produce. These strains blend well with traditional Belgian and Saison strains. Pitch in conjunction with bacteria, like pediococcus, if lactic acid development is desired during aging. We offer CUSTOM BLENDS of our yeast and bacteria strains so you can customize your wild fermentations.
In an industry where people’s creativity knows no bounds, the use of Brettanomyces stands as a testament to the beauty of embracing the wild, the unpredictable, and the extraordinary. So, the next time you raise a glass of your favorite funky farmhouse ale or sour beer, remember the tiny, shockingly wild organism that played a pivotal role in creating that exceptional brew. Cheers, from BSI to your wild side!
References and Further Readings:
White, C., & Zainasheff, J. (2010). Yeast: The Practical Guide to Beer Fermentation (Ser. Brewing Elements Series). Brewers Publications.
Yakobson, Chad. Primary fermentation characteristics of brettanomyces yeast species and their use in the brewing industry. MSc. Thesis. Heriot-Watt University, 2010.
https://beerandbrewing.com/dictionary/sZ3rBkmAXZ/ (article for Craft Beer & Brewing researched and written by Chad Michael Yakobson of Crooked Stave, Denver, CO.)
https://brettanomyces.wordpress.com/
Written by: David Pritchard, Microtechnologist