Statistical analysis of sake-preparation conditions and dimethyl trisulfide formation.

Dimethyl trisulfide (DMTS) is known to be responsible for hineka, an off-flavor that develops during storage, in sake. Previous studies have attempted to elucidate the mechanism of DMTS formation during sake storage, but the mechanism underlying DMTS formation remains unclear. In this study, we determined the sake-preparation conditions that affect DMTS formation. We analyzed 76 sake samples immediately after filtration, which were donated by sake-producing companies. We measured the DMTS concentration in sake after 7 days of storage at 70°C (DMTS-pp) using gas chromatography/mass spectrometry. In the statistical analysis, DMTS-pp was set as the objective variable, whereas the preparation conditions and analytical results for sake were set as the explanatory variables. We used multiple linear regression (MLR) analysis with a stepwise method and partial least squares regression (PLSR) to analyze the data. The statistical analysis showed that the significant factors for DMTS-pp were the average temperature in the moromi mash (Temp ave), the total daily temperature in the moromi mash (Temp sum), the concentration of sulfur-containing amino acids in sake, and the Zn concentration in sake. These factors explained 63.4% of the variance in DMTS-pp according to the MLR analysis and 64.2% according to the PLSR analysis. Further MLR analysis showed that Temp ave in early stage and Temp sum in later stage were important factors for DMTS-pp. This result suggests that the rice dissolution caused by high Temp ave in early stage and yeast cell lysis caused by high Temp sum in later stage contribute to high DMTS-pp.