Fermentation profiling of rice wine produced by Aspergillus oryzae KSS2 and Rhizopus oryzae KJJ39 newly isolated from Korean fermentation starter

Abstract

The objective of this study was to determine the fermentation characteristics of rice wine produced by koji inoculated with Aspergillus oryzae KSS2 and Rhizopus oryzae KJJ39 on moisturized wheat-bran and rice grain. We also compared rice wine samples produced in this study and three commercial Makgeolli. The alcohol content was about 12% higher in the rice wine samples fermented by wheat-bran koji than in the other samples. In all of the samples, the range of pH value was 3.8–4.6 and the total acid was below 0.5. The soluble solid content was highest in the rice wine sample prepared by the wheat-bran R. oryzae KJJ39 koji (15.5°Brix) and overall relatively higher in the samples with wheat-bran koji than rice koji. The content of reducing sugar was twofold higher in rice wine prepared by koji inoculated with R. oryzae KJJ39 than A. oryzae KSS2. The volatile acid content was higher in rice wine produced by the wheat-bran A. oryzae KSS2 koji than the others. In the analyses of five organic acids, A. oryzae KSS2 was found to produce more malic acid and fumaric acid while R. oryzae KJJ39 to do more citric acid, lactic acid and acetic acid. The rice wine sample prepared with the wheat-bran A. oryzae KSS2 koji contained much higher concentration of sucrose, maltose and amino acids. Comprehensively, the results of fermentation profiling suggest that both A. oryzae KSS2 and R. oryzae KJJ39 can be applied to the production of rice wine as a valuable fungal isolate for fermentation start.