Mixed-Fermentation Sour Beer

BJCP 2021:
North America


Mixed-Fermentation Sour Beer is characterized by its complex blend of flavors and aromas, resulting from the unique process of being fermented with a combination of different yeast strains and bacteria. These microorganisms include, but aren't limited to, Saccharomyces (brewer's yeast), Brettanomyces (wild yeasts), Lactobacillus, and Pediococcus bacteria. The result is a harmony of sourness, funkiness, and often fruity notes that can vary widely from one example to another. Historically, this style has its roots in traditional European practices where beer was produced under less controlled conditions than it is today, allowing for the influence of local wild yeast and bacteria. The style represents both historical methods as well as modern craft interpretations of those old practices. Unlike purely wild or spontaneously fermented beers like Lambics or Gueuze, mixed-fermentation sours are more curated concoctions where brewers carefully select their strains for desired effects.

Appearance-wise, these beers can range from pale golden to deep amber hues with varying levels of haze due to the mixed culture fermentations; some aged examples may clear up over time. The carbonation level can also fluctuate depending on the specific production techniques used. On the nose and palate, one might find a tapestry of flavors: tart and tangy notes from lactic acid produced by certain bacteria complemented sometimes by acetic sharpness if vinegar-producing bacteria are present; earthy barnyard characteristics or a ripe fruit bouquet courtesy of Brettanomyces; all supported by a malt base that is typically medium-light to medium-full in body. Sweetness varies but generally takes a back seat to the sour profile.

There's significant overlap with other sour styles such as Flanders Red Ale or American Wild Ales in terms of flavor characteristics and fermentation agents used – each has its own distinctive qualities mostly defined by tradition and regionality but united through their complex interplay between microbes that create their defining sour taste profiles.



In Database
2.9 < 5.6 < 9.3 %


In Database
1 < 11 < 56 IBU


In Database
5 < 8 < 59 EBC
2 < 4 < 30 SRM

Original Extract

In Database
7.5 < 12.8 < 19.4 °P
1.030 < 1.052 < 1.081 OG

Final Gravity

In Database
0.3 < 2.6 < 6.8 °P
1.001 < 1.010 < 1.027 FG

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