The Trouble With Butyric Acid (Nerdy)

Last night I was drinking a gose and noticed a flavor I’ve encountered in some beers soured by Lactobacillus: the faint flavor and aroma of vomit. Delish! It’s never been overwhelming in any beer I’ve encountered, but does tinge the whole affair with unpleasantness. Horse blanket, a touch of compost, vinegar–all of these have their place. Vomit not so much.

I tweeted out my finding and the result was a flurry of information. The culprit here is butyric acid, actually an ester, which is indeed found in human vomit.

Butyric acid is a carboxylic acid found in rancid butter, parmesan cheese, and vomit, and has an unpleasant odor and acrid taste, with a sweetish aftertaste (similar to ether). Butyric acid is a fatty acid occurring in the form of esters in animal fats and plant oils. Interestingly, low-molecular-weight esters of butyric acid, such as methyl butyrate, have mostly pleasant aromas or tastes. As a consequence, they find use as food and perfume additives. 

(Interestingly, it’ …