Impact of koji-making time on sake quality analyzed using gas chromatography/mass spectrometry-based metabolite
Yoshihiro Tamada1, Natsuko Kaneko1, Takuya Asai1
1Hakutsuru Sake Brewing Co., Ltd., 4-5-5 Sumiyoshiminami-machi, Higashinada-ku, Kobe, Hyogo 658-0041, Japan.
Abstract:
Koji-making is a critical process in sake brewing, and the duration of koji-making is a key parameter that influences the quality of rice koji. However, the impact of koji-making time on overall sake quality remains to be fully elucidated. In this study, sake was brewed using rice koji prepared with different koji-making times (45, 55, and 65 h), and the effects of koji-making time on sake quality were investigated. Sensory evaluation revealed that extending the koji-making time resulted in sake with enhanced richness and mellowness. Gas chromatography/mass spectrometry-based profiling of hydrophilic, non-volatile, low-molecular-weight compounds demonstrated that several components, including glucose and erythritol, increased with longer koji-making times. Overall, this study provides quantitative evidence that koji-making time influences sake quality at the component level. Our findings substantiate the empirical notion that rice koji produced with extended koji-making time (i.e., hine-koji) affects sake quality, and provide a basis for the rational design of koji-making conditions tailored to the desired sake characteristics.
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