VIEW ARTICLE    DOI: 10.1094/ASBCJ-37-0169

Dimethyl Sulfide Precursor in Beer. D. W. Hysert, N. M. Morrison, and R. L. Weaver, Molson Breweries of Canada Ltd., Montreal, Quebec H2L 2R5. J. Am. Soc. Brew. Chem. 37:0169, 1979.

A method for determining dimethyl sulfide precursor (DMSP) in bottled beer is described. The DMSP is converted to free dimethyl sulfide (DMS) by heating the degassed beer with alkali (1N) at 100° C for 1 hr. Free DMS is analyzed before and after this treatment by a gas chromatographic headspace technique using a flame photometric detector. Using this method, we surveyed DMSP and DMS levels in 114 commercial bottled beers from Canada, 13 from the U.S.A., and 15 from Europe. These beers had mean DMSP levels of 24, 17, and 6 µg of DMS equivalents per liter, respectively. The ranges of individual values were 2-112, 1-45, and 0-25 µg of DMS equivalents per liter, respectively. The corresponding mean DMS levels and their ranges were 81, 68, and 69 µg/L and 25-154, 40-165, and 24-111 µg/L, respectively. No significant correlation between DMS and DMSP concentrations was observed. First order rate constants were determined for the DMSP to DMS conversion at 70, 85, and 100° C. These rate constants and the energy of activation (31 kcal/mol) for the reactions derived from them support an S-methylmethioninesulfonium type of structure for DMSP. DMSP concentrations rapidly decreased during storage of bottled beer at 40 and 60° C. The increases in DMS concentrations that occurred during this storage did not appear to be directly related to the DMSP decreases.

Keywords: Analytical method, Beer, Dimethyl sulfide, Dimethyl sulfide precursor, Survey