2018 Volume 113 Issue 12 Pages 757-765
We previously reported that the flavor of imo-shochu was changed by increments of amino acids in moromi mash. We therefore investigated the effects of protease activity produced by Aspergillus sp. on the flavor of imo-shochu in this study.
Three strains of Aspergillus luchuensis --KBN 4038, KBN 4041, and KBN 4080-- were selected from 55 candidate strains by enzyme activities. Koji made with the selected strains showed higher enzyme activities than the control, which was made with commercial tane-koji. In particular, the acid protease activities of the selected strains were 1.3 to 1.7 times higher than that of the control. A small scale fermentation test of imo-shochu revealed that the amino acid contents in moromi-mash made with the selected strains increased in proportion with their protease activity.
The concentration of 1-octen-3-ol in imo-shochu using KBN 4038 was 32 times higher than the control.
Sensory evaluation revealed that sweet and koji-like flavors were stronger in imo-shochu made with selected strains compared to the control. The taste of imo-shochu made with KBN 4038 or KBN 4041 was evaluated as sweeter, richer, and less irritating than that with the control. Imo-shochu made with KBN 4080 had fruity and floral flavors, with a sweeter taste compared to the control.
As a result, the enzyme activity of A. luchuensis significantly affected the sensory quality of imo-shochu; accordingly, selection of the Asperigillus strain by enzyme activity would be beneficial for diversification of the imo-shochu flavor.