Microbial and Chemical Analysis of Wild Yeasts from Chambourcin Hybrid Grapes for Potential Use in Winemaking
Open Access
- Author:
- Feng, Chun Tang
- Graduate Program:
- Food Science
- Degree:
- Master of Science
- Document Type:
- Master Thesis
- Date of Defense:
- October 19, 2020
- Committee Members:
- Josephine Wee, Thesis Advisor/Co-Advisor
Edward G Dudley, Committee Member
Ryan John Elias, Committee Member
Robert F Roberts, Program Head/Chair - Keywords:
- Wild yeast
Fermentation
Wine
Microbiology
Fungi
Hybrid grapes
Chambourcin - Abstract:
- Native microbial populations present on grape berries in the vineyard and in winery environments can influence final wine quality. Previous studies on wild yeasts isolated from Vitis vinifera grapes have been reported to enhance wine flavor complexity. Although commercial Saccharomyces cerevisiae has been historically used for winemaking due to its efficiency and reliability in alcoholic fermentation, the role of other fungal populations on fermentation and physicochemical properties of final wines are not well characterized. Chambourcin, a French-American hybrid grape, is the most abundant hybrid grape variety grown in Pennsylvania and is relatively more resistant to cold temperatures and fungal diseases compared to Vitis vinifera grapes. In this study, we isolated and identified wild yeasts from three regional wineries that grow and produce Chambourcin to explore their potential to enhance complexity of final wines. We selected five candidate yeasts, Hanseniaspora uvarum NV192410, H. opuntiae NV192404, Pichia kluyveri NV192402, P. kudriavzevii SM192402 and Aureobasidium pullulans SM190002 and characterized their ability to tolerate varying concentrations of sulfite (0~100mg/L sodium metabisulfite, pH=3) and ethanol (0~12%v/v). We further developed a laboratory scale fermentation system that allowed analysis of non-volatile and volatile compounds derived from inoculated fermentations using candidate wild yeasts using Ultra High-Performance Liquid Chromatography and Gas Chromatography Mass Spectrometry. One hundred and twenty yeast isolates were obtained from three regional vineyards which comprised of 29 unique yeast species. Two wild yeast strains H. opuntiae NV192404 and P. kudriavzevii SM192402 demonstrate tolerance when grown in 8-10 % ethanol and are able to convert sugars to ethanol at a level comparable with control strain S. cerevisiae BY4742 (0.5 g ethanol/g sugar). Concentration of wine important non-volatile compounds were conserved among wild yeasts. Of interest in winemaking, H. opuntiae NV192404 was positively correlated to acetoin and linalool (pleasant buttery and flowery odor) and P. kudriavzevii SM192402 had positive correlation with 1-butoxy-1- ethoxyethane and ethyl 2-hexenoate (fruity aroma). In summary, microbial and chemical analysis of candidate wild yeasts can play a role in fermentation and in wine flavor complexity. Future work will focus on sensory and consumer studies to determine whether the differences of wine flavor can be detected and appreciated.