Thesis
Optimization of fermentation temperature and inoculation timing for use of non-Saccharomyces yeasts to reduce ethanol production in red wines
Washington State University
Master of Science (MS), Washington State University
08/2020
DOI:
https://doi.org/10.7273/000004135
Handle:
https://hdl.handle.net/2376/125097
Abstract
Non-Saccharomyces yeasts have been studied as a means to reduce final ethanol content in wine by metabolism of sugars in grape must prior to inoculation of S. cerevisiae. However, little work has been performed to optimize fermentation factors for non-Saccharomyces yeasts growth and metabolism. The aim of this work was to optimize fermentation temperatures and timing of S. cerevisiae inoculation for use of non-Saccharomyces strains Metschnikowia pulcherrima P01A016 and Meyerozyma guilliermondii P40D002 to reduce ethanol content in red wines. In 2018, temperature optimization was studied. Merlot grape must (120 kg) was distributed into temperature-controlled tanks and inoculated with either Mt. pulcherrima or My. guilliermondii prior to adding S. cerevisiae D254. While control tanks, inoculated with S. cerevisiae alone, were set 25°C, treatments were set to either 15°C or 17.5°C before adding S. cerevisiae on day 3 and temperature adjustment to 25°C. Once fermentations achieved dryness (≤ 2 g/L residual sugar), wines were bottled and stored for 6 months at 7°C prior to sensory analysis. In 2019, timing of inoculation was optimized using Merlot grapes from the same vineyard block as in 2018. Tanks with 85 kg of must were inoculated in triplicate with either S. cerevisiae or Mt. pulcherrima, which were then inoculated with S. cerevisiae on day 0, 1, or 3. Maximum temperatures of all tanks were set to 17.5°C until adjusted to 25°C on day 3. In 2018 fermentations, temperature optimization resulted in ethanol reductions of at least 0.2% in all treatments. Wines inoculated with Mt. pulcherrima at 17.5°C were reduced by 0.8% v/v, and panelists found this treatment to express lower sensory scores for hotness, bitterness, and ethanol flavor. However, optimization of inoculation timing in 2019 was inconclusive due to hindrance of non-Saccharomyces yeasts by reduced initial must temperatures as a result of harvest conditions. In this work, temperature was the most important factor affecting ethanol reductions with use of Mt. pulcherrima and My. guilliermondii. In agreement with previous work conducted using these strains, reducing final ethanol concentrations was achievable without quality loss.
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Details
- Title
- Optimization of fermentation temperature and inoculation timing for use of non-Saccharomyces yeasts to reduce ethanol production in red wines
- Creators
- Tara Cook
- Contributors
- Charles Gould Edwards (Advisor) - Washington State University, Food Science, School of
- 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
- Identifiers
- 99900890781301842
- Language
- English
- Resource Type
- Thesis