Abstract Sydney C. MorganJade J. HaggertyBrittany S. WattersVladimir JiranekDaniel M. Durall

Competition Between Saccharomyces cerevisiae and Saccharomyces uvarum in Controlled Chardonnay Fermentations

Sydney C. Morgan,* Jade J. Haggerty, Brittany S. Watters, Vladimir Jiranek, and Daniel M. Durall  
*The University of British Columbia, 1177 Research Road, Kelowna/BC/V1V 1V7, Canada (sydney.morgan@ubc.ca)

Although Saccharomyces cerevisiae is the most commonly identified yeast during alcoholic fermentation (AF) in winemaking, several species of non-Saccharomyces yeasts can compete with S. cerevisiae throughout AF and may end up dominating. These yeasts, which include strains of Saccharomyces uvarum, are often character-ized as efficient fermenters with high tolerance to ethanol, allowing them to complete AF. S. uvarum is a cryotolerant yeast that produces high levels of glycerol, but low levels of acetic acid, and has been isolated as a dominant yeast from uninoculated fermentations in Canada, France, and New Zealand. We isolated strains of S. uvarum from spontaneously fermenting Chardonnay must at a commercial winery in Canada in 2015 and selected one strain to further assess its fermentative capabilities. To observe the effects of both initial inoculation conditions and fermentation temperature on the competitive abilities of the S. uvarum strain, fermentations of five different inoculation ratios were conducted at two temperatures (n = 3). To determine whether one yeast contributed more strongly to a wine’s volatile profile than the other, post-fermentation samples were taken to analyze the fermentation-derived compounds of the resulting wines using HS-SPME-GC-MS. We found that S. uvarum was more competitive at a lower fermentation temperature, but was unable to outcompete the commercial S. cerevisiae strain unless inoculated at a higher initial concentration. This research is of interest to both the scientific community and the winemaking community, because most S. uvarum strains identified in wineries are non-commercial, and may have potential for enhancing regional character in white wines, which are usually fermented at a lower temperature.

Funding Support: Natural Sciences and Engineering Research Council of Canada; British Columbia Wine Grape Council