Dissertation
Characterization, Vectors and Control of the Wine Spoilage Yeast, Brettanomyces bruxellensis
Doctor of Philosophy (PhD), Washington State University
01/2018
Handle:
https://hdl.handle.net/2376/111021
Abstract
Brettanomyces bruxellensis continues to cause spoilage issues in wines throughout the world. Thus, understanding vectors towards infections and methods of control for this yeast remains a top priority. One such vector may be the spreading of grape pomace, unknowingly containing Brettanomyces, into vineyards as fertilizer or as waste. To investigate the implications of this practice, contaminated pomace samples were placed into storage temperatures (10 weeks) or vineyards (130 weeks). Generally, long term survivability of the yeast was observed as indicated by culturable populations in an enhancement medium. Furthermore, larger populations were recovered in pomace exposed to relatively higher temperatures and containing no microbial competition. To remove the yeast from pomace, heating was effective if sample centers reached at least 50°C for ≥10 min. Besides pomace, infected barrels were assessed to investigate populations at different stave depths and removal strategies using heat. A range of contaminated small (16 L) and large (225 L) barrels varying by age, oak species, and toasting level were obtained. First, the barrels were taken apart into individual staves, sawn into center blocks, and reduced to layers (4 mm thick) or shavings (2 mm depth increments) to assess for yeast penetration using recovery media. Additional blocks were held 30 cm over steam or placed 2 mm into heated water or wine for various amounts of time, with yeast recovery assessed by sawing samples into cross-sections and incubating in nutrient enriched wine. Results showed that populations were larger and at greater depths for staves having longer wine contact time, with French heavy toasted staves being the most contaminated. Steaming for 12 min removed the yeast up to 9 mm, as evidenced by a lack of culturable cells for at least 60 d. Equivalent results were observed using 70° or 80°C water for 30 or 20 min, respectively, or 50°C wine for 120 min. In summary, the collective results from all experiments demonstrated the capacity for B. bruxellensis to survive long-term in both grape pomace and oak barrels, and that eradication of the yeast is possible if certain time/temperature minimums are reached wherever the yeast is located.
Metrics
22 File views/ downloads
20 Record Views
Details
- Title
- Characterization, Vectors and Control of the Wine Spoilage Yeast, Brettanomyces bruxellensis
- Creators
- Zachary Michael Cartwright
- Contributors
- Charles G Edwards (Advisor)Carolyn F Ross (Committee Member)Bhaskar R Bondada (Committee Member)Thomas Henick-Kling (Committee Member)
- Awarding Institution
- Washington State University
- Academic Unit
- School of Food Science
- Theses and Dissertations
- Doctor of Philosophy (PhD), Washington State University
- Number of pages
- 170
- Identifiers
- 99900581510001842
- Language
- English
- Resource Type
- Dissertation