Breeding of the high ethyl caproate-producing sake yeast “Gifu G2”

Sake yeast produces a fruity flavor called “ginjo-ka” during sake brewing. Ethyl caproate is one of the important flavor components of ginjo-ka. In this study, to brew rich-flavored sake, we aimed to breed high ethyl caproate-producing sake yeast strains derived from the Gifu Prefecture yeast strain G. Among the obtained mutant strains, we selected strain Ce18 from small-scale brewing tests because (i) it inherited a high fermentation ability from the parent strain G, (ii) it produced 3.5 times more ethyl caproate than strain G, and (iii) the sake brewed using this strain exhibited a unique fruity flavor and taste. Furthermore, in sake brewing tests with Ce18 at sake breweries, a sake rich in flavor (3.6–8.7 ppm ethyl caproate) and with a dry taste (-1.0–18.3 sake meter value) was produced. From the results, strain Ce18 was named Gifu G2 and was made available to breweries.