UBC Theses and Dissertations
The interaction of two Saccharomyces cerevisiae strains (Lalvin RC212 and Lalvin ICV-D254) during wine fermentation and its effect on fermentation-derived by-products in wine Gustafsson, Frida Sofie
Little is known about the direct effect Saccharomyces cerevisiae strains have on operational wine production during fermentation. Previous research has shown two strains, Lalvin® RC212 (RC212) and Lalvin® ICV-D254 (D254), co-fermenting and occupying > 50% of the yeast population at the end of operational level fermentations. These findings suggest that D254 is competitive in tanks inoculated with RC212. The aims of this study were: (1) to follow the interactions between RC212 and D254 under in-lab and operational fermentations; and (2) to compare the fermentation-derived by-products between in-lab and operational fermentations. Five inoculation ratios of RC212 to D254 were analyzed for in-lab controlled fermentations: a) 1:0; b) 9:1; c) 3:1; d) 1:1; and e) 0:1. During the in-lab fermentations, the strain abundance was analyzed with two methods: 1) microsatellite analysis and 2) a novel strain tracking method using fluorescent quantum dot particles. Operational fermentations at Quails’ Gate Estate Winery, both inoculated and spontaneous, consisted of varying, but defined ratios obtained at the end of fermentation. Strain populations at the operational level were sampled and analyzed solely by microsatellite analysis. Wine samples were analyzed for the following fermentation-derived by-products: acetaldehyde, ethyl acetate, methanol, propanol, isobutanol, active amyl alcohol, isoamyl alcohol, ethyl butyrate, isoamyl acetate, hexanol, and 2-phenylethanol. Regression analysis was used to determine whether these compounds were associated with a specific yeast strain. During the in-lab study, both tracking methods revealed the absence of competition between the yeast strains and populations remained at the inoculated ratio throughout the fermentations. In the operational fermentations, the strain RC212 dominated inoculated fermentations, whereas D254 dominated spontaneous fermentations. During the in-lab study, acetaldehyde, propanol, isobutanol, and isoamyl alcohol significantly increased in concentration as RC212 abundance increased. Meanwhile, ethyl acetate and active amyl alcohol significantly increased as D254 increased; however, in the operational samples, only isobutanol and isoamyl alcohol were shown to be strain specific. Additionally, hierarchical cluster analysis showed that the inoculation treatment of 1:1 most closely resembled the pure D254 treatment, suggesting that D254 has a greater effect on the chemical profile than does RC212 under in-lab conditions.
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