Isovaleric acid
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Isovaleric acid is a short-chain fatty acid with a sensory threshold of 0.3–0.9 mg/L.[1] At high levels, this compound has an unpleasant aroma, usually described as old cheese, rancid, foot-like/dirty socks, goaty, or sweaty, and therefore its presence at higher concentration is undesirable. However at low levels it can add to the flavor "complexity" of a beer or wine, even if its signature aroma is not detected outright.[1][2] Isovaleric acid may potentially be confused with caprylic off-flavor.[2]
Isovaleric acid is usually derived from the use of old hops that have become oxidized, where it is often accompanied by grassy notes.[2] To reduce avoid high levels of isovaleric acid, hops should be fresh or stored in an oxygen-deprived environment (e.g. vacuum bags in a freezer).[2] Isovaleric acid can also be produced in significant quantities by yeast and bacteria (especially from a contamination or wild fermentation).[2] The formation of isovaleric acid during fermentation is likely coupled with leucine (amino acid) metabolism.[1] Brettanomyces is known to metabolize isovaleric acid into ethyl isovalerate, which has a nice sweet fruity flavor.[citation needed]
See also[edit]
- Isovaleric Acid on the Milk the Funk wiki
References[edit]
- ↑ a b c Olšovská J, Vrzal T, Štěrba K, Slabý M, Kubizniaková P, Čejka P. The chemical profiling of fatty acids during the brewing process. J Sci Food Agric. 2019;99(4):1772–1779.
- ↑ a b c d e Habschied K, Košir IJ, Krstanović V, Kumrić G, Mastanjević K. Beer polyphenols—bitterness, astringency, and off-flavors. Beverages. 2021;7(2):38.