Temperature had important effect on yeast growth and on the
levels of volatile compounds.It was observed that the final concentrations of ethyl acetate and some of the higher
alcohols decreased when fermentation temperature increased to 25
◦
C (35 mg/l at 15
◦
C and 27 mg/l at 25
◦C). SO2
stimulated the yeast growth up to certain level and in excess it inhibited the yeast metabolism. Ethanol concentration
slightly increased with the addition of 100 ppm SO2 (8.2 g/l) and decreased with increase in concentration of SO2
(6.2 g/l in 300 ppm SO2). Aeration by shaking increased the viable cell count (from 52×10
6
in the absence of oxygen to
98×10
6in shaking at 30 rpm) but decreased the ethanol productivity (from 7.2 in initial dissolved O2to 6.5 g/l shaking
at 30 rpm).