Vineyard yeast involvement in spontaneous fermentations of chardonnay at Mission Hill Family Estate Winery

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Two groups of yeasts are involved in winemaking: the first group are the non-Saccharomyces yeasts (a large group of yeasts originating from the vineyard) and the second group include strains of Saccharomyces cerevisiae (mainly winery-residents that are responsible for the majority of wine fermentation). Non-Saccharomyces yeasts usually die out in the early stages of fermentation, because of an increasing concentration of alcohol, competition with S. cerevisiae, and by the addition of sulfur dioxide, which is added to almost all commercially-produced wines. Increased consumer interest in novel wine products has led some winemakers to adopt more traditional methods of winemaking that encourage the involvement of vineyard (non-Saccharomyces) yeasts during fermentation, in order to increase wine complexity. Two such methods will be investigated in this project: the first method is 'spontaneous' fermentation, where no commercial yeast strain is added to the pressed grape juice and fermentation is allowed to be conducted naturally, and the second method is 'pied de cuve' fermentation, where the winemaker spontaneously ferments a small amount of juice out in the vineyard, and then uses this as an inoculum for the juice in the winery. Both methods aim to increase the involvement of vineyard yeasts for a more unique final product, but there is a lack of research comparing the two techniques. This project aims to: 1) develop a research partnership between UBC Okanagan and Mission Hill Family Estate Winery; 2) determine the Saccharomyces and non-Saccharomyces yeasts fermenting wines made with a spontaneous or pied de cuve fermentation technique, at varying levels of sulfur dioxide; 3) make recommendations to winemakers regarding the potential benefits of producing wines made using a pied de cuve style of fermentation at low sulfur dioxide levels. Chardonnay fermentations will be sampled during the 2015 vintage, and samples will be taken at multiple stages of fermentation for microbial and chemical analysis. Both non-Saccharomyces species (via next-generation sequencing) and S. cerevisiae strains (via microsatellite strain typing) will be quantified and identified at each stage.