Quantitative Differences in Products of Fermentation by Different Strains of Wine Yeasts

Ninety-eight wine yeast strains belonging to the species Saccharomyces cerevisiae and its variety ellipsoideus were grown in 300-ml quantities of the pasteurized grape juice at 25°C and the yields of ethanol determined. From these results 44 strains were selected for more detailed study. These were grown in grape juice at 12, 25, and 35°C, and in grape juice with added cane sugar at 25°C. The resulting wines were analysed for ethanol, residual reducing sugar, volatile and total acids, glycerol, and acetaldehyde, and the pH values were determined. The final ethanol content varied from 8 to 15 per cent. v/v at 25°C. Although the production of ethanol was slightly higher at 15 than at 25°C the period of fermentation was longer. At 35°C the quantity of ethanol produced varied from 18 to 70 per cent. of that produced at 25°C, depending on the strain. In grape juice containing added sugar the strains showed marked differences in the quantity of ethanol produced at 25°C. Most strains produced more volatile acid at 25 than at 15 or 35°C, but the fixed acid and final pH showed little variation. More glycerol was produced at 25 than at 15°C, certain strains consistently producing more than others. The production of acetaldehyde was investigated with 11 strains, two of which produced high yields particularly at 15°C. The origin and method of storage of the strains are given and their taxonomy is discussed.