Fatty Acids - My Beer Smells Like a Goat!

Fatty acids concentrations are low in wort but increase as fermentation and maturation progresses. Medium-chain acids are a normal constituent of and contribute to the characteristic flavors you associate with beer. When the concentration of these acids becomes high, off-flavors develop.

High concentrations of butanoic and 3-methylbutanoic acids will cause a sickly or "cheesy" off-flavor in your beer. Excessive levels of butanoic acid are usually caused by infections from anerobic bacteria. Excessive amounts of 3-methylbutanoic acid are commonly the result of oxidation of alpha and beta acids from old hops. Other off-flavors attributed to these acids are described as "goaty" and come from hexanoic, octanoic, and decanoic acids being produced in excess during fermentation.

Excessive concentrations of these acids can also cause a decrease in a beer's foam stability and should be avoided for obvious reasons.

Information for this page was adapted from Volatile compounds in foods and beverages By H. Maarse

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