Beer Brewed with Sake Yeast Strain Has Unique Sake-like Flavors

"Sake Yeast Beer” is a beer style characterized by the unique flavor of the sake yeast strain; however, it cannot ferment wort because of the low assimilation ability of maltose. Herein, a sake yeast strain was bred for improved maltose assimilation ability and an original sake yeast strain optimized for a beer brewing environment was developed. The mutant sake yeast strains produced large amounts of isoamyl acetate (3-methylbutyl acetate) and ethyl caproate (ethyl hexanoate) responsible for the ginjo-aroma of sake. A detailed analysis of the volatile components in a small-scale beer brewing test revealed that the beer brewed with BMK3, one of the mutant strains, was composed of many volatile components generated by yeast, such as esters, alcohols, and fatty acids, in comparison to the beer fermented with a general brewer’s yeast. Moreover, in a full-scale beer brewing test using BMK3, the beer was composed of isoamyl acetate and ethyl caproate at 2.3 and 6.7 ppm, respectively. On the sensory evaluation of two beers fermented with BMK3 and a general brewer’s yeast, the beer brewed with BMK3 had the unique characteristics of “ginjo-aroma like fruit,” remaining “sweetness,” and a “rich body but crisp finish.”