The effect of SO2 on the production of ethanol, acetaldehyde, organic acids, and flavor volatiles during industrial cider fermentation

SO2 is widely used in cider fermentation but also in other alcoholic beverages such as wine. Although the authorized limit is 200 ppm total SO2, the International Organizations recommend its total elimination or at least reduction due to health concerns. Addition Of SO2 to apple juice at levels frequently used in industrial cidermaking (100 mg/L) induced significantly higher acetaldehyde production by yeast than that obtained without SO2. Although the practical implications of acetaldehyde evolution under cidermaking conditions has been overcome by research and few data are available, this compound reached levels in two 2000 L bioreactors that may have prevented the occurrence of simultaneous alcoholic and malolactic fermentation. It was observed that malolactic fermentation had a positive effect promoting reduction of acetaldehyde levels in cider fermented with juice, SO2-treated or not. The addition Of SO2 clearly delayed malolactic fermentation comparing to the control, affecting not the onset of the malolactic fermentation but the rate of malic acid degradation. This compound, however, had a stimulatory effect on alcoholic fermentation.