Effects of simultaneous and sequential mixed fermentation of non-Saccharomyces strains and a Saccharomyces cerevisiae strain on the fermentation process and volatile compounds of Mijiu

Summary The combined use of non- Saccharomyces yeasts and Saccharomyces cerevisiae in mixed fermentation is considering as a potential way to improve the flavour characteristics of Mijiu (a traditional rice wine in China). In this study, we investigated the effects of mixed fermentation, including simultaneous and sequential inoculation fermentation, of typical non- Saccharomyces yeast strains ( Saccharomycopsis fibuligera ; Candida glabrata ) and an S. cerevisiae strain on the fermentation process and volatile compounds of Mijiu . The results showed that the fermentation rate of Mijiu was improved by the simultaneous inoculation fermentation of different non- Saccharomyces yeasts and S. cerevisiae . However, the increase of volatile compounds in the simultaneous inoculation fermentation depended on non- Saccharomyces yeast species, although the positive contribution of non- Saccharomyces yeasts to volatile compounds of Mijiu was confirmed in their pure fermentation. The sequential inoculation fermentation significantly enhanced the content or complexity of volatile compounds of Mijiu but with low-fermentation rate. This could be attributed to the change of the number of non- Saccharomyces yeast cells during the mixed fermentation possibly caused by the inhibition of S. cerevisiae with high concentration on non- Saccharomyces yeasts. Our work provided useful information on the mixed inoculation fermentation strategy combining suitable non- Saccharomyces yeasts and S. cerevisiae for improving the fermentation rate and the aroma quality of Mijiu .