American Wild Ale: A Profile

This Style Profile peers under the hood of American Wild Ale, the most interesting style this side of the BJCP.

By Michael Agnew
Illustration by DWITT

When discussing American wild beers, it’s hard to talk about “style.” The Beer Judge Certification Program (BJCP) doesn’t have a listing for it. These beers are relegated to the “specialty ale” category—the catch-all for beers that don’t fit anywhere else. The Brewers Association guidelines list five “styles,” but the descriptors are extraordinarily vague— “American sour ales are very light to black.” The vital statistics like gravities and IBUs simply say, “Varies with style.”


What we are really talking about is a set of beers that don’t fit the classic sour beer styles and that share a single characteristic, fermentation, either primary or secondary, with non-saccharomyces yeast or acid-producing bacteria. The underlying wort is irrelevant to the determination of style. American wild beers can be light or dark, hoppy or malty, strong or sessionable, barrel-aged or not. They may have fruit, spice, or any other adjunct added. Fermentation flavors encompass the tart acidity brought by bacteria like lactobacillus and acetobacter, as well as the leathery, earthy, and barnyard flavors that are the hallmarks of brettanomyces yeast.

These so-called wild fermentations aren’t always really so wild. Brewers can purchase pure strains of brettanomyces and the various bacteria from the same labs that supply them with brewers yeast. Some brewers though utilize strains that exist naturally in the brewery, isolating the cells and culturing them in a lab or simply letting them drop into the still-warm wort in shallow cooling troughs called coolships. Still others rely on the microflora inhabiting the porous wood of used barrels.

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Bacteria and wild yeast can be used as either primary or secondary fermentation agents. For the latter, the wort is first fermented with a standard saccharomyces brewers yeast. Wild critters are introduced in the tank or barrels where the beer is aged or in the bottle at packaging. Because much of the wort’s sugar is consumed during the first fermentation, this method can sometimes deliver a subtler wild character; sometimes, but not always.

Where wild fermentation is the primary fermentation, brewers may forego saccharomyces all together, or they may add a yeast blend that includes brewers yeast as well as brettanomyces and/or bacteria. Sometimes the wort is sent to large, wooden, aging vats called foudres (pronounced FOO der) where the cultures reside. These organisms work slowly, so beer fermented in this way may spend several months to several years in these vats.

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In either case it is the acidification of the wort or beer by these organisms more than the wort itself that defines it as American wild ale. The sour beer program at New Belgium Brewing Company offers a great object lesson in how this works. In its Lips of Faith series, New Belgium produces beers with a staggering array of flavors. Every one of them is built on one of two simple worts: a dark wort called “Oscar” and a light one called “Felix.” Each of the brewery’s many foudres produce beer with a distinct profile. These are blended and combined with fruit or other ingredients to create each unique beer.

Vague though they are, the Brewers Association guidelines for the American wild ales can serve to bring some focus to a discussion of the style. They have three main categories: American-style sour ale, American-style brett beer, and wood- and barrel-aged sour beer. The first and last categories have subcategories for fruited and non-fruited beers.

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About Michael Agnew, A Perfect Pint

Michael has a passion for beer. He is Minnesota's first Certified Cicerone (think sommelier for beer) with the Cicerone Certification Program, and a National Beer Judge with the Beer Judge Certification Program. In addition, Michael is himself an award-winning brewer. He writes a monthly column on beer for the Minneapolis Star Tribune.

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