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South African
Wine Lab Association:

The Diversity and Dynamics of Indigenous Yeast Communities in Grape Must from Vineyards Employing Different Agronomic Practices and their Influence on Wine Fermentation

B. Bagheri, F.F. Bauer, M.E. Setati*

The current study evaluated the diversity of yeast species in Cabernet Sauvignon grape must derived
from three neighbouring vineyards from a similar terroir but on which significantly different management
practices are employed. The fermentation kinetics and yeast population dynamics were monitored from
the beginning to the end of spontaneous fermentation. The grape musts were characterised by distinct
yeast populations comprising oxidative, weakly fermentative and strongly fermentative yeasts. Different
combinations of dominant non-Saccharomyces yeasts were observed in each must, with significantly
different assortments of dominant species, including Starmerella bacillaris (synonym Candida zemplinina),
Lachancea thermotolerans, Hanseniaspora uvarum, Candida parapsilosis and Wickerhamomyces anomalus.
None of these yeast consortia appeared to affect the growth of Saccharomyces cerevisiae or inhibit the
overall progress of fermentation. However, the percentage of fermentative yeasts was positively correlated
with the fermentation rate. Glucose and fructose consumption rates suggested active participation of both
glucophilic and fructophilic yeasts from the onset of fermentation. The data highlight two parameters, viz.
initial cell concentration and yeast community composition, as important fermentation drivers and open
the possibility to predict fermentation behaviour based on the initial composition of the yeast community.

Wine fermentation, yeast dynamics, non-Saccharomyces yeasts, fermentation kinetics

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