UBC Theses and Dissertations
Effect of mixed Saccharomyces strain fermentation on Pinot noir wine Terrell, Emily Elizabeth
Pinot noir has traditionally been fermented by native winery flora; however, the recent practice of single yeast strain inoculation may simplify wine aromas and flavours. Thus, a need exists for yeasts that create the complexity of naturally fermented wines and provide the consistency of commercial strains. It has been suggested that mixed Saccharomyces strains may be capable of this dual role. In this study, three novel Burgundian S. cerevisiae strains were characterized for enological equivalency against five industrial strains recommended for Pinot noir. The volatile compounds produced by these strains along with four Burgundian strain mixtures were quantified in Pinot noir wine to evaluate the hypothesis that mixed S. cerevisiae strains contribute to the complexity of naturally fermented wine. The Burgundian strains were enologically equivalent to the industrial strains in terms of killer phenotype, fermentation kinetics, production of ethanol, glycerol, and acetic acid, conversion of sugar to ethanol, ethanol tolerance, foam production, sulfur dioxide production, and compatibility with malolactic fermentation. The concentrations of most of the 25 compounds quantified in the headspace of Pinot noir wines fermented at 22°C and 27°C significantly differed among yeast strains and between temperatures. Principal component analysis revealed different patterns of volatile production among the industrial, individual Burgundian and mixed Burgundian yeast strains. Mixed Burgundian strains produced greater amounts of most of the higher alcohols than individual Burgundian strains. Additionally, individual and mixed Burgundian strains produced greater amounts of ethyl esters than most industrial strains, but did not differ from one another. In contrast, the pattern of acetate ester production differed between individual Burgundian and mixed Burgundian strains in a fermentation temperature-dependent manner. Cluster analysis revealed that differences in the patterns of volatile production among industrial, individual Burgundian and mixed Burgundian yeast strains extended over the complete volatile profile. Furthermore, cluster analysis of the averaged profiles showed greater overall similarity between the industrial and the individual Burgundian strains than the mixed Burgundian strains. Fermenting Pinot noir with mixed Burgundian yeast strains resulted in unique patterns of volatile production, which holds promise for mixed Saccharomyces products that yield wines of greater complexity.
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