The Okanagan valley of British Columbia, Canada, includes over 130 wineries. This has caused Okanagan winemakers to seek to produce a more unique product by means of spontaneous fermentations. Traditionally, inoculated fermentations are conducted by adding an abundance of a particular Saccharomyces cerevisiae yeast strain to produce consistent and specific chemical and sensory attributes in wines; however, many winemakers are choosing to conduct spontaneous fermentations to achieve more complex characteristics in their wine. Our first objective was to compare S. cerevisiae strain and yeast species diversity and composition between inoculated and spontaneous fermentations of Pinot noir and Chardonnay musts. Our second objective was to determine whether yeast species assemblages, diversity, and composition differed between culture-dependent identification methods using microsatellites and DNA sequencing and culture-independent identification via the Illumina MiSeq platform. Using the culture-dependent method, uniquely different S. cerevisiae populations and yeast communities were found between spontaneous and inoculated fermentations of Pinot noir; however, there was no difference between the two fermentation treatments in Chardonnay. Unexpectedly, both Pinot noir and Chardonnay fermentations included non-Saccharomyces yeasts, specifically Hanseniaspora and Pichia sp., throughout fermentation and in large relative abundances. Culture-dependent or independent analyses had similar results when describing species diversity and composition. The detection by both methods of unique yeast species assemblages and differences in diversity and community structure between inoculated and spontaneous fermentations of Pinot noir musts indicate that both methods are valid. However, the culture-independent method represented a microbial community based on the whole sample rather than a portion of the sample as in the culture-dependent method.

Funding Support: BC Wine and Grape Council, NSERC