Stable Isotope Analysis of Hydrogen and Oxygen in a Traditional Japanese Alcoholic Beverage, Sake, from Niigata Prefecture in Japan and Other Countries.

Stable hydrogen and oxygen isotopic compositions (δD and δ18O values, respectively) were analyzed for "sake," a traditional Japanese alcohol beverage, to assess these values for the identification of its geographic origin. We collected sake (Junmai-shu; made of only rice, water, and koji) and its source water (i.e., brewing water) from breweries in Niigata Prefecture, Japan, and measured the isotopic compositions of water in these samples. The δD and δ18O values for the sake are well correlated with their respective values for the corresponding brewing water (δD; r = 0.92, δ18O; r = 0.80). Furthermore, based on the δD-δ18O cross plot, sake brewed in Niigata Prefecture is distinguishable from that brewed in countries other than Japan. These results imply that this dual isotope (δD and δ18O) analysis is potentially useful in identifying the geographic origin of sake.

Isolation of a non-urea-producing sake yeast strain carrying a discriminable molecular marker.

In the fermentation industry, the traceability of microorganisms during the process is important to ensure safety and efficacy. Ethyl carbamate, a group-2A carcinogen, is produced from ethanol and urea during the storage of food/alcoholic beverages. We isolated non-urea-producing sake yeast car1 mutants carrying a discriminable molecular marker, and demonstrated, by the use of PCR assays, that these mutants are useful for traceability analysis and identification during the sake brewing process.

Polishing properties of sake rice Koshitanrei for high-quality sake brewing.

The Japanese high-quality sake Daiginjo-shu is made from highly polished rice (polishing ratio, less than 50%). Here we showed that the sake rice Koshitanrei (KOS) has an excellent polishing property. Rice grains of KOS had the same lined white-core region as the sake rice Yamadanishiki (YAM). The grain rigidity/hardness of KOS was higher than that of the sake rice Gohyakumangoku (GOM). The loss ratio of KOS after high polishing by an industrial polishing machine was lower than that of GOM. Further, a clear taste of sake produced from KOS was confirmed by sensory evaluation.