Mixed-Fermentation Sour Beer

BJCP 28b

Overall Impression
A sour and/or funky version of a base style of beer.
Aroma
Variable by base style. The contribution of non-Saccharomyces microbes should be noticeable to strong, and often contribute a sour and/or funky, wild note. The best examples will display a range of aromatics, rather than a single dominant character. The aroma should be inviting, not harsh or unpleasant.
Flavor
Variable by base style. Look for an agreeable balance between the base beer and the fermentation character. A range of results is possible from fairly high acidity/funk to a subtle, pleasant, harmonious beer. The best examples are pleasurable to drink with the esters and phenols complementing the malt and/or hops. The wild character can be prominent, but does not need to be dominating in a style with an otherwise strong malt/hop profile. Acidity should be firm yet enjoyable, but should not be biting or vinegary; prominent or objectionable/offensive acetic acid is a fault. Bitterness tends to be low, especially as sourness increases.
Mouthfeel
Variable by base style. Generally a light body, almost always lighter than what might be expected from the base style. Generally moderate to high carbonation, although often lower in higher alcohol examples.
Comments

These beers may be aged in wood, but any wood character should not be a primary or dominant flavor. Sour beers are typically not bitter as these flavors clash. The base beer style becomes less relevant because the various yeast and bacteria tend to dominate the profile. Inappropriate characteristics include diacetyl, solvent, ropy/viscous texture, and heavy oxidation.

History
Modern American craft beer interpretations of Belgian sour ales, or experimentations inspired by Belgian sour ales.
Ingredients
Virtually any style of beer. Usually fermented by Lactobacillus and/or Pediococcus, often in conjunction with Saccharomyces and/or Brettanomyces. Can also be a blend of styles. Wood or barrel aging is very common, but not required.
Commercial Examples
Boulevard Love Child, Cascade Vlad the Imp Aler, Jester King Le Petit Prince, Jolly Pumpkin Calabaza Blanca, Russian River Temptation, The Bruery Rueuze, The Bruery Tart of Darkness