Influence of yeast strain on Shiraz wine quality indicators.

Wine styles are defined by complex and highly diverse chemical compositions. Evidence suggests that some of this complexity is determined by the choice of yeast strain used in fermentation. There are hundreds of different commercially available wine yeast strains that, potentially, provide a means by which winemakers can tailor their wines for different consumer market segments. In this study we evaluated the impacts of fermenting Shiraz must with different yeast strains, with a focus on chemical composition and tannin content of the finished wines. Principal Component Analysis (PCA) of the wines indicated that choice of yeast strain had a strong influence on a number of wine compositional parameters, including tannin. In three fermentation experiments, across two vintages and using different winemaking protocols, a compelling case for yeast strain 'signature' was evident. The results demonstrate that there is an opportunity to use commercial wine yeast diversity to modulate red wine composition and, by implication, the style of finished wines.