Native yeast selection to improve red wine aroma by fermentation at low temperature

MASSERA A.; STURM M.E.; ASSOF M.; ROJO M.C.; JOFRÉ V.; COMBINA M.

Paris, Francia

Simposio; 27th International Specialized Symposium of Yeast “Yeasts for health and biotechnologies” (ISSY); 2009

Aroma and flavor are the main characteristics to determine wine quality and value. The nature and amount of volatile compounds are dependent of multiple factors, such as fermentation temperature and yeast strain used. Therefore, selecting the appropriate strain for each type of fermentation is an adequate strategy to ensure good fermentation performance and to improve the wine flavour. The aim of this work was to select native S. cerevisiae strains to ferment red must at 15ºC and to improve the aroma profile of red young wines. Fourteen S. cerevisiae native strains isolated from natural fermentation were oenological characterized in standardized laboratory conditions. Seven pre-selected strains were evaluated in microvinifications (5L) using Merlot grapes. The strains whose wines had the best analytical and sensorial characteristics were evaluated in red must fermentations at pilot scale (80L). Implantation of S. cerevisiae strains was controled by interdelta PCR. Chemical and sensory analyses were performed. Volatile compounds were quantified by GC/MS. Standardized oenological laboratory tests allowed reducing the number of strains evaluated. The characteristics considered to strain selection in this scale were fermentation rate and purity, ethanol tolerance, low H2S production and killer factor. Seven native S. cerevisiae strains were used to ferment natural must in 5L scale. Native yeasts produced less volatile acidity than commercial yeasts evaluated. Only one native strain was unable to complete the fermentation. MaB-2C, MaE-1C and Bo-1C produced wines with better chemical and sensory characteristics and were selected to be evaluated at the following scale. At pilot scale, MaB-2C wines showed more terpenes level while Bo-1C wines showed significantly higher esters and high alcohols concentrations, and they were related with banana and floral sensorial descriptors. Implantation of native strains at the end of fermentation was higher than 90% in all of the assays. In spite of GC/MS volatile concentration and sensory analyses data were difficult to be correlated; some group of aroma compounds could be associated to sensory descriptors and were useful to strains differentiation. In all the assays the native yeasts showed better oenological attributes than commercial yeasts in the evaluated conditions. MaB-2C and Bo-1C were finally selected to enhance aroma in red young wines production conducted at low temperatures.