In the present study, the relationship between the flavor compounds in sake exhibited at the Annual Japan Sake Awards and the meteorological conditions during grain filling and the properties of rice starch during the 2009 – 2018 brewing years were investigated. The mean concentration of ethyl caproate in sake exhibited at the Annual Japan Sake Awards showed significant correlations with the maximum Baumé, the ratio of sake cake, the gelatinization temperature, the enzyme digestibility of steamed rice grains, and the temperature during one month at grain filling of the Yamadanishiki rice cultivar harvested at Hyogo, but that of isoamlylacetate, isoamylalcohol, and ethylacetate did not. Therefore, when the temperature during grain filling of Yamadanishiki was lower and the enzyme digestibility of steamed rice grain was higher, the mean concentration of ethyl caproate in sake exhibited at the Annual Japan Sake Awards was higher. The present study indicated the possibilities that the meteorological conditions during rice grain filling cause the change in digestibility of sake rice and have considerable influence on the ethyl caproate concentrations in daiginjyo-sake.
The properties of “Gin no iroha”, a new rice cultivar for sake brewing, was examined by comparison with “Kura no hana” cultivated in Miyagi Prefecture in the practical scale production in the 2018 brewing year. “Gin no iroha” had sufficient polishing properties to a 50% polishing rate and higher solubility than “Kura no hana” in fermentation mash. Sake produced from “Gin no iroha” had a rich and soft taste, while that from “Kura no hana” had a light and clean taste. These results suggest that “Gin no iroha” is a compatible cultivar to “Kura no hana” in Miyagi Prefecture.
In shochu brewing, citric acid produced by koji fungus enables stable fermentation. Therefore, any contamination of lactic acid bacteria that have the ability to assimilate citric acid can cause spoilage of the mash. The purpose of our research is to develop a method for early detection of putrefactive lactic acid bacteria by a PCR method using specific gene sequences of putrefactive lactic acid bacteria. Focusing on two types of structural genes(mleP, citT)encoding the putative citrate permease involved in the uptake of citrate in Limosilactobacillus fermentum(formerly Lactobacillus fermentum)enabled us to detect specific lactic acid bacteria that cause putrefaction of shochu mash.