68. Identification of a precursor of 2-mercapto-3-methyl-1-butanol in beer

Shigekuni Noba (1), Nana Yako (1), Minoru Kobayashi (1), Susumu Masuda (1), Masayuki Aizawa (1); (1) Asahi Breweries, Ltd., Moriya , Japan

Technical Session 20: Mashing, Boiling, & Wort
Wednesday, August 17  •  8:15–9:30 a.m.
Plaza Building, Concourse Level, Governor’s Square 14

2-mercapto-3-methyl-1-butanol (2M3MB) imparts an onion-like off-flavor in beer and is speculated to result from hot aeration of brewer’s wort. 2M3MB has been detected after fermentation of a wort spiked with 10 mg/mL of 3-methyl-2-buten-1-ol, the concentration of which did not change before or after hot aeration of the wort. In the present study, we attempted to detect and identify the precursor of 2M3MB that is formed during hot aeration of wort. The potential precursor was purified using distillation, column chromatography, and preparative gas chromatography. The accurate mass of the purified compound was measured using gas chromatography coupled to quadrupole-time-of-flight-mass spectrometry (GC-QTOF/MS), and the obtained mass value was used to calculate the elemental composition. In addition, the molecular structure of the compound was determined from fragment data of tandem mass spectrometry spectra. These data were used to chemically synthesize the potential precursor compound, which was then added to wort for fermentation analysis. The wort supplemented with the test compound contained a proper concentration of 2M3MB after fermentation, indicating that the identified compound was the main precursor of 2M3MB.