Wine starter selection for adsorption activity to control colour of Slovakian wines

The aim of this work was to specifically select autochthonous strains of Saccharomyces cerevisiae to improve colour of wines produced in the area of Little Carpathians (Slovakia) by: (a) preservation of the phenolic compounds, and (b) protection of colour, for red winemaking, or removing of residual colour, for white winemaking. In 2008 and 2009, a total of 50 Slovakian autochthonous yeast strains were pre-selected. The strains were stored in YPD agar and molecular identification was performed to select only the Saccharomyces cerevisiae. After this, 44 strains were chosen and stored at -85°C using the Protect system. To study their aptitude to adsorb grape pigments, the 44 strains, together with 6 Calabrian strains of Saccharomyces cerevisiae previously selected for winemaking, were characterized by micro-winemaking trials, carried out using pasteurized (110°C x 10 min) must from black grapes, pressed after 3 days of cryomaceration at 4°C in contact with skins and seeds. At the end of fermentation, wines were centrifuged at 4,500 rpm for 5 min and analysed for: alcoholic content (by ebulliometer), absorbance at 420, 520, and 620 nm, colour intensity and tint, Folin-Ciocalteu index. Yeasts characterization was performed by two PCR-based typing methods (PCR-RFLP and fluorescence ITS PCR) in order to cluster and preliminarily identify the isolated yeasts. After clustering some yeast members were identified through ITS sequencing. Among the selected yeasts, strains M2VCHU7 and M2FCHU9 exhibit the highest aptitude to adsorb grape pigments, so producing wines with the lowest colour intensity and total phenolic content. These yeasts are able to remove the residual colour from white wines, so allowing refining them. On the contrary, strains M2VCHU6 and M2FVUP4 exhibit the lowest aptitude to adsorb grape pigments, so producing wines with the highest colour intensity and total phenolic content. These yeasts are able to express the chromatic properties of black grapes, giving an improved performance in the production of red wines.