In sake brewing, the steamed rice is used in 2 ways, added to sake-mash and making rice-koji. Rice-koji is made from the steamed rice by using koji starter, and its quality is an important determinant of the aroma/taste of sake. The sake rice Koshitanrei (KOS) was developed in Niigata Prefecture by crossing 2 sake rice varieties, Gohyakumangoku and Yamadanishiki. Recently, we reported the characteristic components/metabolites in sake made from KOS by conducting metabolome analysis using UPLC-QTOF-MS. In this study, to investigate the effect of koji starter and sake rice cultivars on the sake metabolites, we performed small-scale sake-making tests using the above 3 rice cultivars and 3 koji starters. Finally, we demonstrated that some of the characteristic components/metabolites of sake from KOS are affected by the koji starter. Thus, in addition to rice cultivar, koji starter plays an important role for establishment/maintenance of the quality of the final product.
Keywords: Koshitanrei; koji starter; metabolite; metabolome analysis; sake.