Fermentation of Grasevina must with different strains of wine yeasts

Background and Purpose: Two autochthonous Saccharomyces cerevisiae yeast strains (ZIM 1900 from Cabernet Sauvignon grapes and ZIM 1899 from Chardonnay grapes), isolated from the Istria region were tested for their wine production properties. Methods: Fermentative abilities of isolated yeast strains were tested in a small scale using Grasevina must and compared with fermentative properties of wine yeast strain Z-2 (Saccharomyces bayanus), two commercial wine yeasts, denominated as A and B (both Saccharomyces cerevisiae) and yeast microflora naturally present in must. Microfermentations of synthetic VP4 medium were done at 12 and 20 degrees C. Fermentation profiles were monitored by measuring CO2 evolution and CO2 production rate. Reducing sugars, ethanol, total and volatile acids in wines produced by different yeast strains were compared. Data were also compared with synthetic medium fermentation performed in our previous work. Results: Except for residual sugar concentrations and final mass of CO2 produced at used concentrations of inocula, there were no significant differences infermentation rates and basic wine composition between inoculated must fermentations and fermentation performed using naturally present must microflora. It was probably because of considerable contribution of autochthonous yeasts present in must before inoculation. Conclusions: Must fermentation trials conducted with yeasts isolates ZIM 1900 and ZIM 1899 at 12 and 20 degrees C showed good fermentation properties both in synthetic medium and in Grasevina must. The highest average daily specific rate of fermentation at 12 degrees C tvas obtained during the third day with all yeast strains (0.79-0.87g CO2/Lh). The maximum-fermentation rate at 20 degrees C was obtained during the second day (1.92-2.06g CO2/Lh for all fermentations). Contribution of indigenous yeasts to fermentation tvas considerable.