Effects of low pressure and a rectification column on the volatile composition of fermented grape distillate

Fermented crushed Prosecco grapes were distilled using a batch still under normal (100.9 kPa) and reduced pressure (40 or 47 kPa) with and without the rectifying column of the distillation equipment. To improve insight into the behaviour of ethanol and the partitioning of some volatile compounds, each distillate was collected in fractions and analysed for lower volatile alcohols and esters. The results show that the behaviour of ethanol under reduced pressure was more consistent, the proof level higher than at normal pressure and there was a stripping effect on the volatile compounds considered at low pressure. This effect is enhanced when the rectifying column is included. It was concluded that it could be advantageous to use 'vacuum distillation' because it simplifies the operation of the equipment and leads to an overall reduction of the heating required, although there are problems of losses of desirable aromatic compounds