Reduction of volatile acidity of wines by selected yeast strains

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2010-05
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Institute for Biotechnology and Bioengineering, Centre of Genomic and Biotechnology (IBB/CGB-UTAD)
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Herein, we isolate and characterize wine yeasts with the ability to reduce volatile acidity of acidic wines. From a set of 135 yeast isolates, four strains revealed the ability to use glucose and acetic acid simultaneously. Three of them were identified as Saccharomyces cerevisiae and one as Lachancea thermotolerans. Among nine commercial S. cerevisiae strains, strains S26, S29, and S30 displayed similar glucose and acetic acid initial simultaneous consumption pattern and were assessed in refermentation assays. In a medium containing an acidic wine with high glucose–low ethanol concentrations, under low oxygen availability, strain S29 was the most efficient one, conversely, for low glucose–high ethanol concentrations, under aerobic conditions, S26 was the most efficient acid-degrading strain. The influence of different combinations of initial concentration of acetic acid and ethanol on the removal of acetic acid from acidic wines by strains S26 and S29 was also evaluated. Both strains reduced the volatile acidity of an acidic wine (1.0 g l-1 acetic acid and 11% (v/v) ethanol) by 78% and 48%, respectively. Acetic acid removal by strains S26 and S29 was associated with a decrease in ethanol concentration of 0.7 and 1.2% (v/v). Strain S26 revealed better removal efficiency due to its higher tolerance to stress factors imposed by acidic wines. Sulfur dioxide (SO2), in the concentration range of 95-170 mg l-1 inhibits the ability of both strains to reduce the volatile acidity of the acidic wine used under our experimental conditions. Deacidification of wines with the better performing strain S26 was associated with changes in the concentration of volatile compounds but, still within the range of values described for spontaneous fermentations and with apparently no negative impact on the organoleptical properties.
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Volatile acidity removal, deacidification, acidic wines, yeast, acetic acid, ethanol, SO2
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