The impact of indigenous Saccharomyces cerevisiae and Schizosaccharomyces japonicus on typicality of crystal grape (Niagara) wine

Schizosaccharomyces japonicus have been found as dominant yeast species coexisting with Saccharomyces cerevisiae during late stages of spontaneous fermentation of local grapes in Guizhou, China. Therefore, this study further investigated the impacts of the two indigenous yeast species on typicality of crystal grape (Niagara) wine. Five indigenous and one commercial S. cerevisiae strains were firstly selected based on their genotypes and fermentation traits in synthetic medium. All the six S. cerevisiae exhibited high tolerance to glucose, temperature, and SO2. The two killer active strains FBKL2.996 and FBKL2.9126 showed relative higher tolerance capacity of ethanol, pH and osmotic pressure than the other four S. cerevisiae strains. Further pure fermentation of six strains using crystal grape must exhibited different contents of volatile compounds, with commercial strain CECA producing the highest levels of acetate esters (phenethyl acetate), ethyl esters (ethyl caprylate, ethyl hexanoate), n-caprylic acid isobutyl ester, and terpenes (linalool) whereas being ranked the last in the sensory analysis. The co-inoculation of indigenous S. japonicus with each of the six S. cerevisiae strains increased the acetate esters (mainly isoamyl acetate) by 2-3 times in crystal grape wine. The indigenous S. cerevisiae FBKL2.9128 showed the most obvious variation of volatile compounds between pure and mixed fermentation, exhibiting the significant increase of isoamyl acetate, ethyl decanoate, ethyl caprylate, ethyl hexanoate, methyl decanoate, and dodecanal when co-inoculated with S. japonicus. Sugar addition in immature crystal grape juice increased the ethanol, glycerol, and some volatile compounds such as ethyl butyrate, but decreased the volatile compounds with floral and animal odors. The aroma sensory analysis confirmed the decrease of varietal aroma in wines with sugar addition when comparing with wines made from immature crystal grape. The results of this study provide basic information on the impact of indigenous S. cerevisaie and S. japonicus, and sugar addition on typicality of crystal grape wine, which would help to improve the wine flavor made from crystal grape in southwest China.

Automated summary

This study discovered the coexistence of indigenous yeast species Schizosaccharomyces japonicus and Saccharomyces cerevisiae during late stages of spontaneous fermentation of local grapes in Guizhou, China, and investigated their impact on the typicality of crystal grape wine. The results showed that two S. cerevisiae strains exhibited higher tolerance and produced higher levels of killer active strain products compared to other S. cerevisiae strains. Co-inoculation of indigenous S. japonicus with S. cerevisiae significantly increased the acetate ester content in crystal grape wine. Sugar addition increased the content of certain compounds but decreased the varietal aroma.