Dimethyl sulfide (DMS) is a volatile organic byproduct of the brewing process that imparts unwanted flavors in beer. This research aims to develop a method for quantitation of DMS in mash, wort, and finished beer. During the mashing process s-methylmethionine (SMM), an amino acid found in barley, is broken down into DMS. Though much of the DMS is removed during mashing, enough remains to impact the flavor of the finished product. This is due to two factors: DMS has a low flavor threshold of approximately 50 μg/L, and its flavor, often described as tasting like cooked vegetables, contrasts strongly with the flavor profile of the beer. To quantify DMS a flame-photometric detector (FPD) equipped gas chromatograph/mass spectrometer was chosen due to the sensitivity of the FPD to sulfur-containing compounds. Original experiments were complicated by the co-elution of ethyl acetate with the internal standard ethyl methyl sulfide (EMS). The FPD allowed separation of the two signals for quantitation. Samples were analyzed via an internal standard of EMS. The calibration curve was constructed from the ratio of the signal response of DMS to EMS as a function of DMS concentration in μg/L. The R<sup>2</sup> value ranges from 0.995-0.999, and the limit of detection is equal to or less than 20 μg/L DMS, indicating that this method is a reliable measure of DMS concentration below the flavor threshold. The results of this research allow for the refinement of the brewing process and management of consistency between batches of finished product.

Quantitation of dimethyl sulfide in beer using headspace flame-photometric detection and gas chromatography/mass spectroscopy

255th National Meeting (2018)

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