Identification of Saccharomyces uvarum from Spontaneously Fermented Pinot gris in British Columbia’s Okanagan Valley
Garrett McCarthy,* Jay Martiniuk, Sydney Morgan, Dan Durall,
and Vivien Measday
*The University of British Columbia, 2205 East Mall, Vancouver/British Columbia/V6T 1Z4, Canada (email@example.com)
Commercial wines are produced either by inoculating fermentations with known commercial strains of Saccharomyces cerevisiae or by spontaneous fermentations, which rely on yeast from vineyard and winery environments. Spontaneous fermentation is characterized by a diverse succession of yeast genera, species, and strains, with usually one or multiple strains of ethanol-tolerant S. cerevisiae dominating the mid and final stages. One motivation for a winery to use a spontaneous fermentation is that the wine will contain a more complex sensory profile than an inoculated fermentation. This is likely due to the production of a wider range of metabolic by-products from a diverse yeast community. Spontaneous fermentations may also be used because resident yeasts partake in shaping the regional character (terroir) of the wine. In 2013 and 2014, we performed spontaneous fermentations of Pinot gris grapes from an Okanagan vineyard, where yeasts from different stages of fermentation were isolated. Surprisingly, we found that approximately half of the 1500 yeasts isolated from both vintages were strains of S. uvarum; as expected, the remainder of yeasts were S. cerevisiae. S. uvarum is more cryotolerant than S. cerevisiae and produces higher glycerol levels and lower levels of acetic acid; therefore, S. uvarum may be of commercial interest as an alternative yeast species for fermentation at lower temperatures. To characterize the S. uvarum strains isolated in our study and distinguish novel genotypes, we used a set of 11 microsatellite loci from previous studies to perform strain typing. We compared our S. uvarum isolates to S. uvarum strains previously identified in New Zealand. Our preliminary data suggests that we have isolated a population of S. uvarum that is indigenous to the Okanagan Valley of Canada and that it could potentially enhance the fermentation properties and sensory profiles of Okanagan white wines.
Funding Support: Natural Sciences and Engineering Research Council of Canada; British Columbia Wine Grape Council