Thesis
Microbial spoilage of wines: characterization and use of alternative strategies to limit infections by Brettanomyces bruxellensis and Bacillus spp.
Washington State University
Master of Science (MS), Washington State University
2016
Handle:
https://hdl.handle.net/2376/102832
Abstract
Various yeasts and bacteria such as Brettanomyces and Bacillus spp. cause spoilage issues for the wine industry. The overall goal of this work was therefore to determine methods of their control and to characterize their wine spoilage potential. Although the nutritional requirements of Brettanomyces have been published, consideration has not been given towards issues related to nutrient carry-over (the ability for cells to carry vitamins into an otherwise vitamin-omitted medium), strain diversity, or media composition (presence of ethanol). Furthermore, the impact of some bacteria infrequently isolated from wine on final product quality is not understood. The objectives were to (a) determine vitamin requirements of B. bruxellensis and evaluate strategies to remove these nutrients from wine as a means to limit growth, and (b) identify and characterize unidentified bacteria isolated from a spoiled wine. Of the vitamins studied, biotin was consistently required by a number of strains of B. bruxellensis without or with 10% ethanol present. Concentrations as low as 0.002 µg/L biotin reduced yeast populations. Removal of the vitamin from a red wine using egg white fining or through addition of avidin, a protein naturally present in egg white that irreversibly binds the vitamin, significantly reduced the maximum populations of two B. bruxellensis strains. Three different species of bacteria, Bacillus megaterium, B. pumilus, and Paenibacillus polymyxa, were isolated and identified from a spoiled wine. In general, these isolates could each grow in media of low pH containing lower amounts of ethanol (<10%) or sulfite (<0.2 mg/L molecular SO2), conditions similar to some grape musts prior to alcoholic fermentation. Growth in a grape juice was characterized by increases in titratable (TA) and volatile (VA) acidities. In conclusion, removal of biotin reduced growth of B. bruxellensis while use of sulfites greater than 0.4 mg/L molecular SO2 generally inhibited Bacillus spp. and related bacteria.
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Details
- Title
- Microbial spoilage of wines
- Creators
- Nicolas Hogrefe Von Cosmos
- Contributors
- Charles G. Edwards (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
- 99900525174801842
- Language
- English
- Resource Type
- Thesis