Jocelyn Bernier-Lachance is an experienced homebrewer with over ten years of experience. He is also a trained microbiologist who has worked for companies such as Lallemand, Gallicus Craft Brewery, and La Chope à Malt/Beer Grains.
Wild yeasts are becoming increasingly popular in microbreweries in Quebec and across the country. When we think of wild yeasts, we immediately imagine a beer aged in a barrel with “funky” aromas. They are often unknown, yet they are responsible for the first fermented drinks! Modern beer yeast is the result of decades of experience in selecting certain properties, eliminating others, and achieving more consistent results.
The most well-known species of wild yeast belong to the genus Brettanomyces. Its name means “British fungus.” In 1904, N. Hjelte Claussen of the New Carlsberg Brewery in Copenhagen discovered that strong English-style beers underwent a second fermentation caused by this yeast. Brettanomyces are also associated with the Dekkera genus. Without going into the details of its genetics, let us simply remember that it is actually the same yeast.
What sets Brettanomyces apart from Saccharomyces cerevisiae, the traditional beer yeast? First and foremost, it’s their ability to digest sugars. The presence of certain enzymes (alpha-glucosidase) allows Brettanomyces to break down more complex sugars than traditional yeast. This means that Brettanomyces can digest very complex sugars that traditional yeast cannot. Thanks to their voracity, beers fermented with wild yeasts can reach a final gravity close to 1.000, or even below. In contrast, the final gravity of a beer fermented with traditional yeast rarely drops below 1.005.
When it comes to taste, the range of flavors can be very diverse depending on the species of Brettanomyces that is chosen. Even within the same species, there can be a lot of variation. Just like humans, yeasts evolve by mixing their genetic material with each other. However, over time, humans have put enough pressure on Saccharomyces cerevisiae to make it lose the ability to mix its genetic material with other species. As a result, Saccharomyces cerevisiae does not lose its desirable properties nor acquire new ones as it multiplies. In general, Brettanomyces claussenii give fruity aromas reminiscent of pineapple while Brettanomyces lambicus give more “funky” aromas (barnyard, hay, leather, etc.). Take the time to read the description of the yeast you want to use to avoid any unpleasant surprises!
Jocelyn Bernier-Lachance M.Sc., Mcb.A.
- Tonsmeire, M., American Sour Beer: Innovative Techniques for Mixed Fermentations, Brewers publications, Boulder, Colorado, United States, 2014.
- White, C. and Zainasheff, J., Yeast: The Practical Guide to Beer Fermentation, Brewers publications, Boulder, Colorado, United States, 2010.