Abstract Detail

Mycological Section

Morgan, Sydney [1], Benson, Natasha [1], Scholl, Chrystal [1], Durall, Daniel M. [1].

The effects of initial sulfur dioxide addition on wine yeast populations during spontaneous fermentations of Pinot gris.

Wine is the product of complex interactions between grape must, bacteria, yeasts, and fungi. The main fermentative yeast in winemaking, Saccharomyces cerevisiae, is rarely present on grape surfaces and is instead a winery-resident yeast. S. cerevisiae is either introduced into fermentations deliberately through inoculation with specific commercial strains, or it spontaneously enters fermentations via the air or winery equipment. Many different strains of S. cerevisiae are used in winemaking, and many strains may be present in a single tank or barrel during fermentation, especially when the wines are allowed to ferment spontaneously. Sulfur dioxide is added to commercially-produced wines, both prior to alcoholic fermentation and just prior to bottling. It performs many functions for the winemaker, as it is both a strong antioxidant and an antimicrobial agent. The addition of sulfur dioxide prior to alcoholic fermentation can help remove unwanted bacteria and yeasts from the grape must. Although the effects of sulfur dioxide addition on spoilage bacteria and total yeast communities have been well-documented, few studies have focused on the effects of this initial sulfur dioxide treatment on the S. cerevisiae strains participating in fermentation. This is important to determine, because different strains of S. cerevisiae are known to produce different chemical and sensory profiles. This study aims to address this gap in knowledge by investigating the effects that three different levels of sulfur dioxide addition (0, 20, or 40 mg/L SO₂) have on the diversity and composition of S. cerevisiae strains present during spontaneous fermentations of Pinot gris at a commercial winery in British Columbia. Each of these treatments was replicated in triplicate in new 225L French oak barrels. Samples were taken for microbial analysis at three stages of fermentation. Yeast isolates were identified to the strain level using microsatellite analysis. Differences in strain diversity and composition between different treatments will be presented and discussed.

1 - University of British Columbia, Biology, 1177 Research Road, Kelowna, BC, V1V 1V7, Canada

Keywords:
Saccharomyces cerevisiae
wine grape
yeast
microsatellite
fermentation.

Presentation Type: Oral Paper:Papers for Sections
Session: 22
Location: Salon 1/The Shaw Conference Centre
Date: Monday, July 27th, 2015
Time: 3:45 PM
Number: 22001
Abstract ID:1119
Candidate for Awards:MSA Best Oral Presentation Award by a Graduate Student