Originally isolated by scientists at Guinness, brettanomyces is a wild yeast that grows on the skins of fruit. Its name means British yeast because the scientists at Guinness thought the unique flavors of English ales came from secondary fermentation by brettanomyces in oak barrels. They weren’t wrong, but brettanomyces is also everywhere. Shortly after its discovery, brett, as it has come to be known, was shunned by the industrial beer producers as a beer spoiler. It produces acetic acid and has several components that are identifiable off-flavors: ethyl acetate (nail polish), ethylphenols (literally produced in a beaver’s castor sacs, a gland near the beaver’s anus (this is the barnyard, sweaty saddle, horse blanket, or medicinal aroma), ethylguaicols (spicy, woody, vanilla, or bacon/smoky), ethyl butyrate (vomit), and isovaleric acid (literally the smell of foot odor and cheese). Except in Belgian saisons and Belgian lambics, the use of wild fermentation and utilization of brett ceased and the crazy array of flavors that the wild yeast can impart disappeared.
So why would anyone want to have a beaver sac, sweaty horse saddle, smelly foot, vomit beer? Well, have you ever had an industrially-produced burger? A burger that tastes exactly like all other burgers that came before it with nothing that is even a little off about it, a burger without even a texture that stands out? Well, those industrially-produced burgers are a lot like the beer market today, especially for brewers. We’ve had decades of industrial beer and our palettes are seeking out these different flavors; our sense of adventure is pushing these process changes (really reversions to old world production processes). Craft brewers have learned the art of making very clean beer, very hoppy beer, making very malty beer, making beer with very high IBUs and with very high alcohol content. Now we’re trying to replicate these old styles of beer and have found that the components of brett flavors – horse blanket, rat taint, funky foot odor – are actually quite pleasant if balanced with other normal beer flavors and in doses that are not overwhelming.
We’ve also learned how to control certain aspects of the yeast’s flavor/aroma production during fermentation and storage. We know that with large amounts of oxygen, the yeast is prone to acetate production and that the yeast will metabolize all kinds of molecules left over from normal fermentation/packaging/filtering: glucose, diacetyl, oxygen, etc., and that can be really good for long-term storage for beer (this aspect alone would explain why bottle conditioning with brett is so popular).
Also, these “off-flavors” in low doses, in a soft blend with other normal beer flavors (hops and malt) and some other off-flavors (lactic acid being the most common), can yield a delicious beer. Anyone who’s had a Saison Dupont, a Lindeman’s, or Duchesse de Bourgogne, you’ve had a beer with some brett fermentation.
I know the idea of having a beer with hints of nail polish, beaver musk, horse blanket, or smelly feet sounds terrible, but the reward of having a beer that tastes so different than any industrially-made beer is worth the risk. If you’re feeling bold and adventurous, try a beer by Crooked Stave, Casey Brewing and Blending, or look for the word “Brett” on a bottle at the local liquor store. You won’t be disappointed with the adventure.
Robert Alan Wendeborn is a former cellar operator at Ska Brewing and current lead cellar operator at Tin Roof Brewing in Baton Rouge, Louisiana.
