Fermentation of Grasevina must with different strains of wine yeast

Background and Purpose: Two autochthonous Saccharomyces cerevisiae yeast strains (ZIM 1900 from Cabernet Sauvignon grapes and ZIM 1899 from Chardonnay grapes), isolated from 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. Micro-fermentations of synthetic VP4 medium were done at 12 and 20 ^o C. Fermentation profiles were monitored by measuring CO_2 evolution and CO_2 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 CO_2 produced at used concentrations of inocula, there were no significant differences in fermentation 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 ^o C showed good fermentation properties both in synthetic medium and in Grasevina must. The highest average daily specific rate of fermentation at 12 ^o C was obtained during the third day with all yeast strains (0.79 - 0.87 g CO_2/Lh). The maximum fermentation rate at 20 ^o C was obtained during the second day (1.92 - 2.06 g CO_2/Lh for all fermentations). Contribution of indigenous yeasts to fermentation was considerable.