Medium and acetification conditions
A white wine from the Montilla-Moriles region (southern Spain) with
an ethanol concentration of 11.5±0.5 %(v/v) and an initial acidity of 0.4%
(w/v), expressed as g of acetic acid¥100 mL–1 of medium was used.
Experiments were carried out in a Frings 8L fermenter working in a
semi-batch mode. For a specific type of wine, the operational variables
that can usually be modified are: temperature, final ethanol concentration,
unloading percentage of the medium, loading flow rate and air-flow
rate. This study compared three different operational conditions. In all
cases, temperate (31°C), final ethanol concentration (0.5±0.1 %v/v),
final acidity (10.0±0.2% w/v) and unloading percentage of the medium
(75%) were the same for all experiments, but loading and air-flow rates
were modified.
The bioreactor was fully automated. Loading, unloading, control and
monitoring operations were performed via a previously programmed
computer. A semi-continuous operational mode was used. Therefore,
once it was partially unloaded, a new cycle was started by adding fresh
wine. The experimental process was repeated at least four times for
each case.