The effects of copper and high sugar concentrations on growth, fermentation efficiency and volatile acidity production of different commercial wine yeast strains

The effect of high Sugar concentrations or the presence of copper residues on fermentation efficiency and volatile acid (VA) production were examined for selected commercial wine yeast strains. Fermentation rate as measured by accumulated mass loss appeared to be least affected by high Sugar concentrations during the first few days of fermentation for strains VIN13, WE14, N96 and RJ11 it was, however, only fermentations using VIN13, WE372, N96 and L2056 that contained less than 11 g/L fructose after 21 days. VIN13 and RJ11 produced the lowest VA in the 21 degrees, 25 degrees and 28 degrees Brix musts. Fermentation efficiency of six strains was also Studied in must containing 0.25 mM Cu2+. Results indicated that strains NT50, Collection Cepage Cabernet (CC) and D80 were not significantly affected, whereas VIN13, NTI12 and RJ11 contained significantly more glucose and fructose after fermentation in the must containing copper. Copper addition also increased VA production, with strains RJ11 and NT50 being the most affected.