Saccharomyces uvarum is a cryotolerant yeast specie that naturally occurs in spontaneous fermentations. It has been observed to contribute positively to fermentation and final wine quality and at least one commercial S. cerevisiae / S. uvarum blend exists (Enartis), as well as a S. cerevisiae / S. uvarum hybrid yeast (Maurivin). The aim of this study was to observe the interactions between a commercial S. cerevisiae yeast strain and an indigenous S. uvarum strain at two temperatures in controlled Chardonnay fermentations.
- Commercial yeast Lalvin QA23 and indigenous yeast S. uvarum SU01 were inoculated into sterile-filtered Chardonnay juice from South Australia in five different ratios (1c | 0u, 10c | 1u, 1c | 1u, 1c | 10u, 0c | 1u).
- Fermentations were conducted at both 15 and 24°C on small scale (250 ml glass Schott bottles).
- Sulphur dioxide and pH measurements were also conducted on the juice before fermentation.
- Samples were taken from the must on days 1,3,5,7 and 10 to measure glucose and fructose concentrations as well as yeast ratio / cell density.
- On day 10 the wines (some not finished with fermentation yet) were analysed for 26 secondary metabolites.
- Fermentations at 24°C were faster than fermentations at 15°C regardless of which yeast strain dominated.
- S. cerevisiae dominated in the 10c | 1u and 1c | 1u fermentations at both temperatures.
- At 15°C S. uvarum was more competitive and managed to maintaine a 25% abundance in the 1c | 1u fermentations, better than its performance in the 24°C fermentations.
- In the 1c | 10u fermentations S. uvarum dominated.
- The fermentations that were dominated by S. uvarum had the highest concentrations of secondary metabolites.
- S. cerevisiae / S. uvarum fermentations generated a unique volatile profile when compared with the single-strain fermentations.
SIGNIFICANCE OF THE STUDY
The study has various limitations in that it was done on small scale and no sensory analysis was done. However, it does indicate that the use of S. uvarum strains in isolation or co-inoculation could potentially lead to the production of unique quality wines.
Sydney C. Morgan, Jade J. Haggerty, Vladimir Jiranek, Daniel M. Durall (2020). Competition between Saccharomyces cerevisiae and Saccharomyces uvarum in controlled Chardonnay wine fermentations. Am J Enol Vitic. 71: 198-207; published ahead of print January 29, 2020 ; DOI: 10.5344/ajev.2020.19072
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