Project Title: Microbiology and Chemistry of Washington Wines
Project Duration: 2013-2015
Principal Investigator: C.G. Edwards
Organization: School of Food Science, Washington State University, Pullman, WA 99164-6376
Phone: 509-335-6612; Email: [email protected]
Cooperator: J.K. Fellman (Washington State University, Pullman, WA)
Role: analytical methods for phenolics
Cooperator: D.A. Glawe (Washington State University, Prosser, WA)
Role: molecular identification of yeasts.
Cooperator: J.F. Harbertson (Washington State University, Prosser, WA)
Role: analytical methods for phenolics.
Cooperator: T. Henick-Kling (Washington State University, Richland, WA)
Role: wine processing/microbiology.
Cooperator: J. Lee (USDA-ARS, Parma, ID).
Role: analytical methods for phenolics/student committee member.
Cooperator: C.F. Ross (Washington State University, Pullman, WA)
Role: sensory methods development/student committee member.
Cooperator: G. Unlu (University of Idaho, Moscow, ID)
Role: molecular analysis of Brettanomyces/student committee member.
Studies related to the ability of Brettanomyces to metabolize phenolics present in grape cultivars. Overall, these experiments demonstrated that (a) Brettanomyces are not able to metabolize tartaric acid esters of phenolic acids present in red wines, (b) culturability of Brettanomyces may or may not indicate formation of 4-ethylphenol/4-ethylguaiacol (e.g., culturable cells can be recovered but volatile phenols are not produced), and (c) growth and metabolism by the four strains studied was more dependent on the strain rather than the wine. Significant interactions between ethanol (12 to 16% v/v) and storage temperature (12° to 21°C) were observed for two strains of Brettanomyces. In general, strains grew well in wines containing 12% to 14% ethanol at ≥15°C. Culturabilities of strains decreased in all wines kept at 12°C or in wines containing 16% ethanol. At 15%, growth depended on strain with I1a more resistant to this concentration of ethanol (growth at 18° and 21°C) than F3. Chitosan was observed to be ineffective against killing two strains of Acetobacter isolated from commercial Washington red wines. Finally, research with non-Saccharomyces yeasts isolated from Washington grapes was initiated. In general, the non-Saccharomyces yeasts evaluated (C. californica, C. oleophila, Mt. pulcherrima, My. caribbica, My. guillermondii, or W. anomalus) reached populations in excess of 107 cfu/mL but did not completely metabolize glucose or fructose, unlike that of fermentations conducted by Saccharomyces. Based on an initial principal component analysis, differences in aroma were noted between C. californica, My. caribbica, and S. cerevisiae.
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