Thesis
Determining Fermentation Parameters and Mechanisms Responsible for Alcohol Reduction in Wine by Metschnikowia pulcherrima and Meyerozyma guilliermondii
Washington State University
Master of Science (MS), Washington State University
2023
DOI:
https://doi.org/10.7273/000005109
Abstract
Non-Saccharomyces yeasts can reduce wine ethanol content when used in mixed culture fermentations with Saccharomyces, thus influencing quality. Two non-Saccharomyces isolates from Washington State, Metschnikowia pulcherrima and Meyerozyma guilliermondii, show this potential when sequentially inoculated into wine fermentations prior to S. cerevisiae. However, for these strains, fermentation conditions, including optimum temperature or sulfite content, hadn’t been established, nor the fate of carbon during sugar metabolism. The aim of this work was to determine fermentation parameters and mechanisms for ethanol reduction by these species. Hence, Mt. pulcherrima, My. guilliermondii, or S. cerevisiae (control) were each inoculated at 106 CFU/mL in 300 mL synthetic grape juice media containing 0.0, 0.2, 0.4, 0.6, or 0.8 mg/L molecular (m) sulfur dioxide (SO2) and incubated at 10°, 15°, 20°, 25°, or 28°C for growth and sugar utilization. Temperature affected Mt. pulcherrima (p<0.0001) and My. guilliermondii (p<0.0001) populations, but both were inhibited by ≥0.6 mg/L mSO2 regardless of temperature. Interactions among temperature, day, and sulfite concentration affected non-Saccharomyces sugar utilization (p<0.0001), with the greatest sugar utilization occurring between 20° and 25°C (p<0.0001). Selected parameters were applied to evaluate Mt. pulcherrima performance in sequentially inoculated standard (24°Brix) and high (28°Brix) sugar Chardonnay ferments. While no wines reached dryness (<2 g/L sugar), those containing Mt. pulcherrima yielded 1.1% and 0.5% v/v less ethanol in 24°Brix (p=0.026) and 28°Brix (p=0.033) ferments, respectively, than the S. cerevisiae wines. To study ethanol reducing mechanisms, Mt. pulcherrima and My. guilliermondii were individually or sequentially inoculated at 105 CFU/mL into media for substrate utilization and byproduct formation. Both yeasts grew with ethanol as a sole carbon source, and yields of glycerol, biomass, and succinic acid were higher than S. cerevisiae while carbon dioxide and ethanol yields were lower (p≤0.05) in sequential inoculations. This series of studies identified optimum fermentation temperatures for Mt. pulcherrima (20°C) and My. guilliermondii (25°C) as well as sulfite tolerance for each species (≤0.4 mg/L mSO2) to apply towards reducing ethanol in wines originating from high-sugar juice. Additionally, this work identified that these isolates produce lower alcohol wines by directly consuming ethanol and/or divert sugar towards biomass or organic acids.
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Details
- Title
- Determining Fermentation Parameters and Mechanisms Responsible for Alcohol Reduction in Wine by Metschnikowia pulcherrima and Meyerozyma guilliermondii
- Creators
- Heather Nicole Carbon
- Contributors
- Carolyn F Ross (Advisor)Thuy Bernhard (Committee Member)Franck Carbonero (Committee Member)
- Awarding Institution
- Washington State University
- Academic Unit
- Food Science, School of
- Theses and Dissertations
- Master of Science (MS), Washington State University
- Publisher
- Washington State University
- Number of pages
- 134
- Identifiers
- 99901019235701842
- Language
- English
- Resource Type
- Thesis