The evolution of acetic acid during yeast growth was followed
using either unsupplemented grape juice or grape juice supplemented
with 1 g/l of acetic acid (Fig. 1). For both fermentations,
three steps in acetic acid evolution can be observed. In unsupplemented
grape juice, acetic acid concentration increases from the
beginning of the alcoholic fermentation to the middle exponential
growth phase, then it decreases until yeast growth stops and finally
increases slightly until the end of the fermentation. In supplemented
grape juice, the first step where acetic acid concentration
increased disappears. Acetic acid concentration seems to remain
almost unchanged until the middle of the exponential growth
phase and then it decreases, this decrease being more pronounced,
as compared to the unsupplemented grape juice. The yield factor