Defining and exploiting the indigenous microflora of grapes
| dc.contributor.advisor | Jiranek, Vladimir | |
| dc.contributor.advisor | Borneman, Anthony | |
| dc.contributor.author | Caliani, Natalia Soledad | |
| dc.contributor.school | School of Agriculture, Food and Wine | |
| dc.date.issued | 2024 | |
| dc.description.abstract | Management practices and environmental factors influence yeast diversity in vineyards and wineries, which affects subsequent fermentations. Through bioprospecting and diversity profiling, valuable yeast strains can be discovered, and key drivers of community composition explored. This is a critical step in defining and utilising the indigenous grape microflora. Vineyards host a complex microbial ecosystem, with yeast species playing a vital role in wine fermentation and influencing sensory attributes. While Saccharomyces cerevisiae is used globally for wine fermentation, other Saccharomyces and non-Saccharomyces yeast species in vineyards and uninoculated fermentations are gaining attention for their unique metabolic features. This research focused on exploring the diversity within the non-Saccharomyces yeast group in local Australian vineyards, aiming to understand and leverage their potential in winemaking. The first part of this study investigated the impact of seasonal rain patterns and fungicide spray regimes, conventional vs. biodynamic, on yeast diversity in the Pewsey Vale Riesling vineyard, South Australia, . Fungal diversity was assessed using both culture-dependent and culture-independent methods across three consecutive seasons. Despite variations in seasons, minimal differences in yeast community profiles were observed between biodynamic and conventional treatments. Fungicide resistance testing on isolates revealed similar susceptibility patterns between strains from biodynamic and conventionally managed grapes. Results revealed minor differences in yeast diversity between conventional and biodynamic grapes post-fungicide spraying, diminishing over time. Higher yeast diversity was observed in conventional juice right after pressing, highlighting the impact of fungicide sprays, particularly those containing sulfur and copper, on yeast survival. Copper sulfate and copper oxychloride, sulfur exhibited the most toxic effects on yeast, which is crucial for growers planning fungicide spraying strategies. In the second part of this study, yeast performance during fermentation was explored, considering factors such as ethanol concentration, pH level, temperature, sulfur dioxide addition, and nutrient availability. Autochthonous yeast isolates from Pewsey Vale and additional isolates from Chalmers Merbein vineyard, Victoria, were pre-screened for their fermentation profile and sulfur dioxide resistance. Five isolates, Hanseniaspora, Kazachstania, Metschnikowia, Torulaspora, and Saccharomyces, showed potential for application in the wine industry, exhibiting desirable characteristics in Riesling and Shiraz grape juice fermentations. In conclusion, this study contributed significantly to understanding yeast population dynamics in vineyards and underscored the potential of non-Saccharomyces yeast species in winemaking. The comprehension of how management practices influence yeast diversity in the vineyard, as well as their subsequent impact on fermentation performance and quality, was elucidated. Autochthonous yeast phenotyping identified isolates with potential for incorporation into the winemaker's toolbox based on SO, resistance, ethanol, glycerol, and aromatic volatile production. The insights gained are invaluable for grape growers, vineyard managers, and winemakers, guiding informed decisions to optimise vineyard microbial 'terroir' and enhance winemaking outcomes. | |
| dc.description.dissertation | Thesis (Ph.D.) -- University of Adelaide, School of Agriculture, Food and Wine, 2024 | en |
| dc.identifier.uri | https://hdl.handle.net/2440/144683 | |
| dc.language.iso | en | |
| dc.provenance | This electronic version is made publicly available by the University of Adelaide in accordance with its open access policy for student theses. Copyright in this thesis remains with the author. This thesis may incorporate third party material which has been used by the author pursuant to Fair Dealing exceptions. If you are the owner of any included third party copyright material you wish to be removed from this electronic version, please complete the take down form located at: http://www.adelaide.edu.au/legals | en |
| dc.subject | native | |
| dc.subject | indigenous | |
| dc.subject | yeast | |
| dc.subject | vineyard | |
| dc.subject | grape | |
| dc.subject | uninoculated fermentation | |
| dc.subject | non-Saccharomyces | |
| dc.title | Defining and exploiting the indigenous microflora of grapes | |
| dc.type | Thesis | en |
Files
Original bundle
1 - 1 of 1
No Thumbnail Available
- Name:
- Caliani2024_PhD.pdf
- Size:
- 12.09 MB
- Format:
- Adobe Portable Document Format