In this study, the distribution of lactic acid bacteria (LAB) in typical sweet potato shochu mash was investigated. The number of bacterial cells peaked on the second day of the second-stage fermentation and gradually decreased as the fermentation process progressed. Sequences of 16S rRNA genes in isolated LAB revealed that the majority of LAB strains in the sweet potato shochu mash belonged to Lactobacillus plantarum, L. fermentum, and L. casei groups. Investigation of physiological characteristics showed that the L. casei group had high ability to assimilate citric acid; in fact, resulting increases in lactic acid, formic acid, and acetic acid were confirmed. The laboratory scale fermentation test using the characteristic LAB revealed changes in organic acid compositions in the second stage fermented mash, and in flavor components in shochu, increases in the levels of diacetyl and diethyl succinate-- both of which were derived from LAB-- were particularly prominent. Furthermore, sensory testing confirmed the influence of LAB. Taken together, the results indicate that certain LAB in sweet potato shochu mash influence the quality of the final shochu product.
In sake brewing, rice polishing is one of the important processes that affect the quality of high-quality sake --such as Daiginjyo-shu-- using highly polished rice. In general, a similar-figures-polishing (SFP) ratio is required for high-quality sake brewing. Here we set 2 polishing programs (P1 and P2) with different polishing parameters and compared the effect of these programs on the SFP in the high polishing of 2 sake rice varieties (KOS:Koshitannrei and TAK:Takanenishiki). The results indicated that P2 was more suitable for SFP than P1. Further, both the crushing rate of the polished rice (CRP) and loss ratio during polishing (LRP) of KOS were lower than those of TAK, and the shape of the polished rice of KOS was closer to the SFP than that of TAK.