brettanomyces

Brettanomyces is a genus of yeast in the family Saccharomycetaceae commonly referred to in beer geek circles as "Brett". Under a microscope, the yeast bodies can appear ovoid to long cigar-shaped. In the presence of oxygen, the yeast may produce ample acetic acid (vinegar). In beer, flavor characteristics are most commonly described as "barnyard" or "horse blanket". Strains of Brett may also produce catty, wet bandage, antiseptic, grapefruit, clove, mousey and other flavors. Brettanomyces may be used by brewers as a single brewing yeast, in combination with another traditional brewing yeast, or in combination with bacteria like Lactobacillus or Pediococcus. Brettanomyces may be added to a beer by intentionally pitching a culture into wort, subjecting wort to barrel storage in inoculated barrels, or more traditionally via the Belgian method of "spontaneous fermentation" whereby wild yeasts are allowed into the brewhouse through open windows and into cooling wort exposed to the air.