Sydney C. Morgan,* Garrett S. McCarthy, Chrystal M. Scholl, Natasha L. Benson, Brittany S. Watters, and Daniel M. Durall
*The University of British Columbia, 1177 Research Rd, 372 Science Building, V1V 1V7, Canada (sydney.morgan@ubc.ca)

In modern-day winemaking, producing consistent wines year after year is often desirable. To achieve this, many winemakers add sulfur dioxide (SO2) and commercial yeasts to their fermentations to prevent the growth of unwanted microbes and ensure that fermentation will complete without undesirable by-products. However, there has been a shift in recent years, partially driven by consumer preferences, for wines produced with minimal input by the winemaker, for a more true expression of the grapes and the wine region they’re grown in. To investigate the implications of this shift, experimental fermentations were conducted at two wineries in the Okanagan Valley to assess the potential for introducing minimal intervention techniques into conventional cellars. At the first winery in 2014, we studied how different levels of SO2 at crush (0, 20, and 40 mg/L) can alter which yeasts conduct uninoculated fermentations. All treatments were dominated by a high diversity of commercial Saccharomyces cerevisiae strains, and each treatment had a significantly different strain assemblage, resulting in measured differences in wine sensory profiles. At the second winery in 2015, a pied de cuve inoculation factor was added, where vineyard-specific yeasts were used to initiate fermentation. The effect of two levels of SO2 added at crush (0 and 40 mg/L) and two types of fermentation (uninoculated and pied de cuve fermentations) were compared. All four treatments were dominated by a diversity of indigenous Saccharomyces uvarum strains, and fermentations with different SO2 treatments contained significantly different strain assemblages as well as unique wine sensory profiles. Pied de cuve inoculation did not significantly impact the fermentation or final wine. These results are of particular interest to winemakers looking to introduce minimal intervention techniques into their winemaking practices, while mitigating the risks associated with uninoculated and unsulfited fermentations.

Funding Support: Natural Sciences and Engineering Research Council of Canada; American Society for Enology and Viticulture; The British Columbia Wine Grape Council