Diversity of regional yeast can be influenced by geography, grape cultivars and the use of SO₂, but at single vineyard scale in China, the impact of these factors on yeast population, particularly Saccharomyces cerevisiae, is not well studied. Here, we characterised yeast species and dynamics during spontaneous fermentations with/without SO₂ using eight typical grape cultivars from Yuma vineyard in Ningxia wine region of China. Results show that distribution and abundance of yeast species varied by grape varieties, fermentation stage and SO₂ treatment. A number of 290 S. cerevisiae isolates were further classified into 33 genotypes by Interdelta fingerprinting. A prevailing role of grape varieties in shaping the genetic divergence of S. cerevisiae in Yuma vineyard was observed, as compared to the impacts of fermentation stage and SO₂ treatment. Pre-selected S. cerevisiae strains were subjected to vinification with Cabernet Sauvignon and Chardonnay. All strains completed fermentations but the physiochemical parameters and volatile profiles of wines were strain-specific. Some indigenous S. cerevisiae yielded more desirable aroma compounds compared to the commercial strains, among which NX16 and NX18 outcompeted others, therefore having potential for use as starters. This study provides comprehensive analysis on yeast diversity at vineyard scale in Ningxia. Information on the vinification using indigenous S. cerevisiae is of great value for improving Ningxia wine regionality.

This study investigated and addressed the harm caused by high ethanol levels (above 16 % vol) to the quality of industrial Cabernet Sauvignon wines through aging in oak barrels with three types of wood grains and three toasting levels. Our findings demonstrated that differences in chemical indexes between the initial and final wines were not entirely due to the oak barrels. Barrels with medium grains and heavy toasting stabilized the wine's colour and minimised the loss of red tones; this effect was associated with phenolic components. Wood-unrelated volatiles were responsible for the considerable variations in volatile profiles; these differences were characterised by a decrease in alcohols, alongside an increase in ethyl esters, enhancing the fruity and floral attributes of the final aged wines. High-ethanol wines aged in medium-grained and heavily toasted barrels exhibited the best characteristics. These findings provide information to address concerns that a high ethanol content compromises wine quality.