Analysis of implantation dynamics and ethanol reduction of a low-ethanol yeast starter in real wine conditions

CUELLO R.A.; COMBINA M.; MERCADO L. A.; CIKLIC I.

Bariloche

Simposio; 34th International Specialized Simposium on Yeast (34 ISSY).; 2018

CONICET

Lately, wine industry has been looking for disrupting methodologies to reduce alcohol content without compromising wine sensory characteristics. Increment in the alcohol concentration have been related with global warming and viticulture management strategies to obtain wines with improved polyphenolic features (e.g. sweet tannins). In previous laboratory-scale assays, we have demonstrated that the insertion of the pdc2Δ519 mutation in Saccharomyces cerevisiae wine yeast strains, can reduce the ethanol concentration up to 1.89% (v/v) without affecting the fermentation performance. This difference in alcohol production between mutant and control strains was observed in culture media and natural grape musts previously pasteurized. However, verification in real vinification conditions is still lacking. The aim of this work was to evaluate our reducing mutant yeast strain in natural grape must fermentation at pilot-scale, including an ethanol reducing commercial strain as a positive control. In order to diminish the natural microbiota of must and consequently improve the implantation of mutant strains, two minimal invasive treatments (microwave and centrifugation) were applied to fresh grape musts. Fermentation in non-treated grape must was also included as control and the implantation dynamics of the pdc2Δ519 mutant strain was monitored during the whole process. The results showed that the pdc2Δ519 mutant strain was largely dominant during the vinification with implantation percentages higher than 70% after only 24h, and reaching values over 90% with a good performance of alcoholic fermentation. However, ethanol reduction was at best 0.4% v/v with little difference between treated and non-treated grape must. This trend has been previously observed in other studies performed with natural must. Our results suggest that the inhibition of the ethanol reduction effect under natural conditions is not a consequence of a substrate competition and other interaction mechanisms may be involved.