Onion-like off-flavour in beer: Isolation and identification of the culprits

Abstract

Beer with an onion-like off-flavour is found to contain two unusual sulphur compounds: (1-methylethyl)-thiirane and 2-mercapto-3-methyl-1-butanol. The off-flavour is attributable to the latter, previously unknown compound. The methods used are: extraction of beer with trichlorofluoromethane, GC analyses of extractives and reference compounds, using a sulphur sensitive flame photometric detector, and GC-MS. Both of the new sulphur constituents are synthesized and their structures ascertained by NMR and MS. © 1988 Carlsberg Laboratory.