Butyric Acid
Butyric Acid is a carboxylic acid that is produced by aenarobic bacteria during sour mashing production such as Clostridium butyricum, C. kluyveri, and Fusobacterium nucleatum [1]. It is often described as a vomit or rancid cheese aroma and flavor. This is not to be confused with Isovaleric Acid which has a more "feety" aroma and flavor, and is produced by Brettanomyces. Brettanomyces can convert Butyric Acid into Ethyl Butyrate at low levels [2].