Beyond Dimethyl Sulfide: The Significance to Flavor of Thioesters and Polysulfides in Canadian Beers

Abstract

During prior investigations into the important beer flavor component dimethyl sulfide, traces of other sulfur compounds appeared in gas chromatographic profiles obtained with a flame photometric detector. We investigated the potential that these low-level compounds have for contributing to the sulfury character of some Canadian beers. Concentration was best achieved by purging the beer with inert gas and adsorbing the compounds on a short column of molecular sieve (type 13X), from which they could be flushed into a cold trap. Gas chromatography and mass spectrometry showed that the trapped components comprised methyl thioesters and dimethyl polysulfides. Quantitation required reverse elution of adsorbed compounds from the sieve with pentane followed by gas chromatography with flame photometric detection on the pentane concentrates. A survey of Canadian beers showed that thioesters are unlikely primary contributors to sulfury characters; however, an indirect role or the possibility of synergism cannot be ruled out. In contrast, dimethyl trisulfide is an important component of Canadian beer flavor, and levels appeared to correlate with taste-panel rankings for sulfury character. Analyses on worts indicated the thioesters resulted from fermentation, whereas the polysulfides derived primarily from malt.