Thesis
Optimization of yeast nutrient additions based on must sugar concentration and impact on microbial wine spoilage
Washington State University
Master of Science (MS), Washington State University
2014
Handle:
https://hdl.handle.net/2376/102685
Abstract
Although winemakers commonly use nitrogen additions to ensure complete fermentation of high sugar musts, interactions between sugar concentration and yeast nitrogen requirements are not well studied. In addition, excessive levels of residual nitrogen not metabolized during alcoholic fermentation may increase the risk of subsequent Brettanomyces spoilage. To study these relationships, synthetic grape juice media were prepared to contain different concentrations of yeast assimilable nitrogen (YAN) and fermentable sugar. Media were inoculated with S. cerevisiae strain ECA5 or Uvaferm 228 at 105 cfu/mL and once fermentation activities ceased, wines were inoculated with one of two strains of B. bruxellensis. Musts that initially contained ≤250 g/L sugar and 150 mg N/L YAN attained dryness (≤2 g/L residual sugar) within 750 hr while those containing 270 or 295 g/L sugar became stuck even at the highest nitrogen concentrations. Under these conditions, YAN composition had a minor effect on fermentation durations, residual sugar concentrations, or H2S production. Although higher YAN concentrations in musts increased quantities of residual nitrogen in the v resulting wines, Brettanomyces growth was not affected. In fact, Brettanomyces required ≤6 mg/L YAN to reach populations of 107 cfu/mL. While high-Brix musts may not require additional nitrogen to complete fermentation, residual nitrogen did not increase the severity of Brettanomyces infections.
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Details
- Title
- Optimization of yeast nutrient additions based on must sugar concentration and impact on microbial wine spoilage
- Creators
- Bradford Charles Childs
- Contributors
- Charels G. Edwards (Degree Supervisor)Jeffri C. Bohlscheid (Degree Supervisor)
- 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; [Pullman, Washington] :
- Identifiers
- 99900525095701842
- Language
- English
- Resource Type
- Thesis