3.2.3 Vacuum distillation
Here, the process of distillation is carried out under reduced pressure – known as a ‘vacuum’. The vacuum lowers the boiling point of the ethanol, meaning that other volatile flavour chemicals (such as alpha acids in the hops) are less affected, and the flavour remains closer to the original. Under the vacuum, the boiling point of the ethanol reduces from 78 °C to approximately 34 °C. This, therefore, allows the ethanol to be removed before the temperature of the distillation apparatus reaches the boiling point of the volatile flavour components.