3.3. Production of ethanol
Fig. 4 demonstrates the time course of ethanol concentration in
all cases. In general, the amount of sugar consumed by yeast is
proportional to the alcoholic concentration of the must. Similarly,
as seen in Figs. 2 and 3, the ethanol yield rate was proportional to
the sugar consumption rate during fermentation. However, unlike
general grape wine fermentation, a linear correlationwas observed
between fermentation time and ethanol production, especially at
the middle stage of fermentation. Based on the measured ethanol
concentration over 20 days of fermentation, 6 linear plots (data not
shown) were constructed with strong correlation (coefficient of
determination, r2 ¼ 0.975e0.998). Therefore, the equations can be
used to estimate the ethanol concentration of fermenting blueberry
wines. Although a difference in ethanol production rate during
fermentation was observed, the final ethanol concentrations in
wines were similar for all samples and ranged from 12.3 to 13.2%.