Effects of Pure and Mixed-Cultures of Saccharomyces cerevisiae and Williopsis saturnus on the Volatile Profiles of Grape Wine

Non-Saccharomyces yeasts are being recognised for their ability to produce wines with unique character. This study assessed the production of volatiles by co-inoculating Saccharomyces cerevisiae and Williopsis saturnus. Laboratory-scale fermentations were carried out using pure and mixed-cultures of S. cerevisiae and W. saturnus at a ratio of 1:1000. The mixed-culture fermentation was dominated by S. cerevisiae, while W. saturnus had an early growth arrest. Changes of oenological parameters and volatiles were similar in both the mixed- and the S. cerevisiae monocultures. A range of volatiles was formed with alcohols and esters constituting the majority of volatiles produced. Volatiles initially present in the grape juice, particularly (E)-2-hexen-1-ol, 1-hexanol, trans-2-hexenal and n-hexanal, were metabolized. Wines produced using mixed-cultures closely resembled those fermented by the S. cerevisiae monoculture but acquired minor flavor characteristics from the initial presence of W. saturnus. These findings suggest that the ratio of S. cerevisiae and W. saturnus is critical to the survival of the non-Saccharomyces yeast and the impact on the perceivable characteristics of the resultant quality and flavor of wines.