Analysis of metabolites in Japanese alcoholic beverage sake made from the sake rice Koshitanrei

Multifunctional-separation-mode ion chromatography method for determining major metabolites during multiple parallel fermentation of rice wine

Facile and effective analysis methods are desirable for elucidating the behaviours of metabolites during fermentation reactions. Herein, a multifunctional-separation-mode ion chromatography (MFS-IC) method was developed for the simultaneous monitoring of major metabolites during multiple parallel fermentation, including those related to central carbon metabolism (saccharification, glycolysis, alcoholic fermentation, and the tricarboxylic acid (TCA) cycle). The use of two types of sulfo-modified size-exclusion columns and phthalic acid as the eluent allowed the separation of oligosaccharides (disaccharides, trisaccharides, and tetrasaccharides), glucose, pyruvate, and major organic acids during the TCA cycle (cis-aconitate, citrate, iso-citrate, malate, fumarate, and succinate but not α-ketoglutarate) from other non-target analytes. The MFS-IC method was successfully applied to monitoring the major metabolites in the rice wine brewing process. This approach can contribute to an improved understanding of metabolite behaviour during fermentation without requiring the use of expensive advanced instrumentation methods such as liquid chromatography-mass spectrometry and gas chromatography-mass spectrometry.

Whether the Research on Ethanol-Water Microstructure in Traditional Baijiu Should Be Strengthened?

Baijiu is a unique and traditional distilled liquor in China. Flavor plays a crucial rule in baijiu. Up to now, the research on the flavor of baijiu has progressed from the identification of volatile compounds to the research on key aroma compounds, but the release mechanism of these characteristic compounds is still unclear. Meanwhile, volatile compounds account for only a tiny fraction, whereas ethanol and water account for more than 98% of the content in baijiu. By summarizing the ethanol-water hydrogen bond structure in different alcoholic beverages, it was found that flavor compounds can affect the association strength of the ethanol-water hydrogen bond, and ethanol-water can also affect the interface distribution of flavor compounds. Therefore, the research on ethanol-water microstructure in baijiu is helpful to realize the simple visualization of adulteration detection, aging determination and flavor release mechanism analysis of baijiu, and further uncover the mystery of baijiu.

Effect of koji starter on metabolites in Japanese alcoholic beverage sake made from the sake rice Koshitanrei

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.