Isovaleric Acid
Introduction
Isovaleric Acid, also known as 3-Methylbutanoic acid, is an organic compound with the formula (CH3)2CHCH2CO2H. The flavor and aroma are often described as rancid Parmesan, or foot odor. it is not to be confused with Butyric Acid.
Production in Beer and Wine
Brettanomyces can create isovaleric acid [1]. The compound generally takes a few months to produce in beer by Brettanomyces. Brettanomyces breaks down leucine present in beer into isovaleric acid (controversial, but generally accepted) [2][3].
Isovaleric acid can also be produced by a bacteria that lives naturally on human skin and is responsible for foot odor called Staphylococcus epidermidis. It does so by degrading leucine, an amino acid present in sweat [4]. Leucine is also present in beer [5].
Other bacterias, including species and strains of Streptococcus (more so) Lactobacillus (less so) can produce various amounts of isovaleric acid from leucine, as well as other compounds from other carboxylic acids [6]. This may be the reason that sour mashes often have a rancid cheese off flavor (although this may also be at least partially due to Butyric Acid production during Sour Mashing).
References
- ↑ Wikipedia article
- ↑ Botha, Janita J. Sensory, chemical and consumer analysis of Brettanomyces spoilage in South African wines. March 2010. Pg 2, 13, 17, 18
- ↑ Oelofse, Adriaan. Investigating the role of Brettanomyces and Dekkera during winemaking. December 2008.
- ↑ Ara K, Hama M, Akiba S, Koike K, Okisaka K, Hagura T, Kamiya T, Tomita F. Can J Microbiol. 2006 Apr.
- ↑ Hall, Nutfield, Redhill, Surrey. Amino Acid Esters in Beer. Brewing Research Foundation. July 14, 1980.
- ↑ Helinck, Le Bars, Moreau, and Yvon. Ability of thermophilic Lactic Acid Bacteria To Produce Aroma Compounds from Amino Acids.