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UBC Theses and Dissertations

Characterization of vineyard-associated wine yeasts and flavonoid profiles of Pinot Noir grapes in the Okanagan Valley of British Columbia, Canada Cheng, Elaine


Wine is a product of grape juice fermentation by yeast. Terroir is a term that encompasses all environmental factors and interactions at a specific geographical site, resulting in the development of regional-specific microbial strains and differences in grape phenotypes. The objectives of this study were to determine the distribution of vineyard-associated wine yeast strains, identify potential regional-specific wine yeast strains and characterize the flavonoid profile of Pinot Noir grapes among three different sub-regions in the Okanagan Valley (OV), a major wine region in British Columbia, Canada, in the 2017 vintage. Grape samples were collected from thirteen vineyards among three sub-regions of the OV, namely Kelowna (KE), Naramata-Penticton (NP) and Oliver-Osoyoos (OO), within a week prior to the winery harvesting date, which occurred between September 2017 and October 2017. Vineyard-associated S. cerevisiae and S. uvarum on the grape samples were enriched and isolated from spontaneous fermentations conducted in the lab. The isolates were genotyped by microsatellite analysis. Regional-specific wine yeast strains were differentiated from commercial wine yeast strains using Bruvo’s genetic distance. The anthocyanin and flavonol profiles of Pinot Noir grapes were analyzed by HPLC/UV-vis/MS and the tannin profile was analyzed by a spectrophotometric method. In total, 10 commercial S. cerevisiae strains, 22 potentially indigenous S. cerevisiae strains, 2 previously isolated S. uvarum strains from OV, 1 previously isolated S. uvarum strain from Hornby Island and 2 newly discovered S. uvarum strains were isolated in this study. S. cerevisiae strains is genetically more closely related within each sub-region as compared to between sub-regions. The population structure of the S. cerevisiae strains was significant at the regional level. The anthocyanin content were significantly lower in Pinot Noir grapes isolated from OO as compared to KE. Furthermore, the relative abundance of methoxylated anthocyanin and flavonol compounds were higher in Pinot Noir grapes collected in OO as compared to KE. Therefore, the flavonoid profile of Pinot Noir grapes was significantly affected by sub-regional terroirs. Further research is required to determine how regional-specific wine yeast strains and the flavonoid profile of Pinot Noir grapes affect the quality of wine production in the OV.

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