Flavour extraction during gin production using different distillation methods

Gin distillation is a flavouring process through extraction of flavour compounds from essential oils in plant materials (botanicals) by the usage of a neutral alcohol-water solution. There are two principal distillation methods used: steep and vapour infusion. Investigating influencing parameters for extraction of terpenes during the vapour infusion process showed that the botanical ratio had the greatest effect on the extraction, but the ethanol concentration of the charge had a significant influence on the extraction levels of oxygenated monoterpenes. By fractioning and measuring the distillate at different time points a kinetic study was carried out to investigate the extraction dynamics of flavour constituents during gin distillation, where steep infusion was best described with a first-order rate equation and vapour infusion by using a logistic function. A comparison of the behaviour of three classes of terpenes solubilized in an ethanol solution, distilled in a batch still with two modes of reflux and with or without a packed column and two pressures (atmospheric and partial vacuum) was carried out. The results showed a clear difference in behaviour between monoterpenes, with highest concentration in the distillate in the beginning, and oxygenated terpenes and sesquiterpenes, with an increase of the concentration towards the end of the distillation. Simulation of two different distillation settings were carried out with a heterogeneous approach using the non-random two liquid (NRTL) activity coefficient model to represent the interactions within the liquid between terpenes and water and ethanol.