Differences in Brewing Characteristics between Saccharifying Microorganisms, Rhizopus and Aspergillus, for the Fermentation of Rice Wine

Abstract

Saccharifying microorganisms are critical to brew various rice wines, as traditional alcohol beverages produced and consumed widely in Southeast Asia. Rhizopus and Aspergillus are the most common saccharifying fungi, which could trigger the diversity in production and quality of rice wines. This study focused on investigating the difference in brewing characteristics between Rhizopus and Aspergillus, including 4 Rhizopus strains and 4 Aspergillus strains. Their performance was analyzed and compared in the process of saccharification and co-fermentation with Saccharomyces cerevisiae for rice wine production. In the saccharification process, all Rhizopus strains produced higher reducing sugar concentration, hydrolytic enzymes’ activities and organic acids, especially lactic acid concentration compared with all Aspergillus, while Aspergillus showed their advantage in producing amino acids. This result demonstrated Rhizopus’s stronger saccharifying and acid-producing ability. In the co-fermentation with yeast, Rhizopus was more conducive to the fermentation in rapidly consuming sugars and producing ethanol. Rhizopus brought relatively more organic acids, especially lactic acid again into rice wine, while Aspergillus provided relatively more amino acids. However, comparing the volatile flavor compounds in saccharification and co-fermentation, both Rhizopus and Aspergillus made less contribution to rice wine, and these compounds could be produced mainly by the yeast. These results suggested that the saccharifying fungi might mainly influence the taste of rice wine, and they could also bring a diversity of aroma by the co-fermentation with yeast. This work provided a reference for understanding the roles of saccharifying microorganisms and their rational application in brewing and quality control of rice wine.

Keywords: Rice wine, Saccharifying microorganism, Rhizopus, Aspergillus, Brewing characteristics