Yeast Diversity during Spontaneous Fermentations and Oenological Characterisation of Indigenous Saccharomyces cerevisiae for Potential as Wine Starter Cultures.

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.

Selection of indigenous Saccharomyces cerevisiae strains in Shanshan County (Xinjiang, China) for winemaking and their aroma-producing characteristics.

In order to select potential indigenous Saccharomyces strains, diversity of indigenous Saccharomyces strains in Shanshan County (Xinjiang, China) was preliminarily analyzed. Twenty-one genotypes were found through interdelta fingerprinting analysis. According to this result, representatives of each genotype were chosen to test the enological criteria. After tests of fermentation characteristics and growth ability, eight strains were finally selected as starters to further fermentation of Merlot must for aroma analysis and sensory evaluation at the same testing conditions, with one commercial strain F15 as control. Each strain of Saccharomyces cerevisiae produced individual volatiles in different concentrations and combinations which significantly influenced resulting wine flavour. Except of LFP522, all indigenous isolates produced more concentration of esters than F15. Higher concentrations of linalool, ß-damascenone and citral, associated with S. cerevisiae LFE1809, considerably distinguished this strain from the others. Sensory evaluation present the Merlot wine fermented by LFE1225 isolated from Merlot, had the highest sensory score.