Screening and identification of precursor compounds of dimethyl trisulfide (DMTS) in Japanese sake

Dimethyl trisulfide (DMTS) is involved in the unpalatable aroma of stale sake, called "hineka"; however, the mechanism underlying the formation of DMTS during the storage of sake has not been elucidated. This paper investigates the precursors of DMTS in sake. An experiment using [methyl-d(3)]-methionine showed that Strecker degradation of methionine plays a minor role in the formation of DMTS. Separation of components in sake by cation exchange resin revealed that DMTS precursors are present in the acidic/neutral fraction rather than in the basic one. Purification of the DMTS precursor compounds was carried out through several chromatographic steps, measuring DMTS-producing potential as an index. High-resolution ESI-MS and 1D/2D NMR experiments enabled the identification of one of the precursor compounds as 1,2-dihydroxy-5-(methylsulfinyl)pentan-3-one.