Influence of Three Non-Saccharomyces Yeasts on Fermentation and Volatile Components of Italian Riesling White Wines

In this study, three commercial non-Saccharomyces yeasts, i.e., Torulaspora delbrueckii, Metschnikowia pulcherrima and Lachancea thermotolerans were tested in combination with Saccharomyces cerevisiae to produce Italian Riesling white wines, with the fermentation progress, physical and chemical indexes of white wine, volatile profile and aromatic property of resulting white wines determined and compared, in order to elucidate their influences on the aroma quality of white wines. Results showed that, all fermentations were completed successfully, but the growth of M. pulcherrima was more easily inhibited by the proliferation of S. cerevisiae. Moreover, the ethanol concentrations of white wines from mixed fermentations were lower than that of S. cerevisiae single inoculation. Volatile compounds were detected by HS-GC-IMS, and a total of 34 volatiles were obtained. Wines inoculated with M. pulcherrima contained the highest signal intensities of ethyl caproate, ethyl isovalerate, ethyl 2-methylbutyrate, hexyl acetate, γ-nonolactone, δ-octanolactone, hexanol, 2,3-butanedione and linalool, the overall aromatic property was greatly enhanced. Wines conducted by mixed fermentation using T. delbrueckii/S. cerevisiae and L. thermotolerans/S. cerevisiae contained higher intensities of ethyl octanoate, propyl acetate, ethyl propionate and α-terpinene, and the aroma and sensory characteristics of these two pairs were similar, both better than the wine fermented singly by S. cerevisiae. Moreover, principal component analysis could better distinguish the wines produced by different mixed fermentation processes. In conclusion, this study showed that the mixed fermentation using non-Saccharomyces yeasts/S. cerevisiae pairs played an important role in the improvement of the aroma of white wine.