The secondary fermentation of Saccharomyces oviformis (strains Epernet and Varna-1) was studied using dry apple wine with low alcohol content (5%-6% vol). The influence of the carbon source concentration, pH, ethanol concentration, and nitrogen sources on the specific ethanol productivity was revealed. Yeast sediment from the primary fermentation was subjected to autolysis and further used as a nitrogen source. Using an additional hydrolysis by acid proteinases, the amino nitrogen concentration in the autolysate increased rapidly up to 800 mg/L. The favorable effect of the hydrolyzed yeast autolysate on the sugar assimilation, especially CO2 pressure, was demonstrated. The yeast autolysis was performed also after pH correction with ammonium phosphate solutions reaching a balanced ratio between amino nitrogen (of organic and non-organic origin) and phosphorus. A comparative analysis of the initial apple juice, dry apple wine, and the obtained low-alcohol sparkling apple wine was made.
- Copyright 1993 by the American Society for Enology and Viticulture