Mixed fermentation with an aroma-producing yeast strain screened from the wild grape on Zhongtiao Mountain affects aromatic components of the wine

Abstract:

[Background] Aroma-producing yeast can endow wine with unique aroma. Therefore, the isolation and screening of excellent aroma-producing yeast strains is of great significance for brewing the wine with regional characteristic flavor. [Objective] Aroma-producing yeast strains were screened from the wild grape growing on Zhongtiao Mountain, identified, and characterized for the physiological and biochemical properties. Further, we applied the strain with the strongest aroma to wine fermentation and studied its effect on aromatic components of the wine. [Methods] The aroma-producing yeast strains were isolated with plate-streaking method and then identified based on the molecular evidence. The strain with the strongest aroma was used for mixed fermentation with Saccharomyces cerevisiae F15. The aroma components of the wine were analyzed by gas chromatograph-mass spectrometer (GC-MS). The content of aroma components was determined with semi-quantitative method. [Results] A total of 13 strains was isolated. The D1/D2 region sequence of the 26S rRNA gene indicated that these strains belonged to five genera of Issatchenkia, Torulaspora, Pichia, Saccharomyces, and Rhodotorula. The strain Issatchenkia orientalis XS-6 with the strongest aroma was selected for further study. It could tolerate the highest ethanol concentration of 8% and NaCl concentration of 6% and showcased the most vigorous growth at 38 ℃. A total of 31 aroma components were detected in wine fermented with I. orientalis XS-6 and S. cerevisiae F15. The total content of aroma substances in the wine produced by mixed fermentation increased by 19.8% compared with that by single strain fermentation. The total content of aroma compounds increased by 19.8%, and the content of 11 aroma components, especially phenylethanol with rose aroma, increased significantly. The content of alcohols and esters increased by 19.6%, and seven new esters such as ethyl vanillate and dibutyl phthalate were detected. [Conclusion] The aroma-producing yeast stain XS-6 has good tolerance to ethanol, NaCl, and temperature. Mixed fermentation of XS-6 with S. cerevisiae F15 significantly affects the aromatic components of Syrah wine, which suggests that XS-6 may have a potential application value in improving wine flavor.

Key words:wild grape on Zhongtiao Mountain;aroma-producing yeast;mixed fermentation;Issatchenkia orientalis;aroma components