The effect of distillation conditions and alcohol content in 'heart' fractions on the concentration of aroma volatiles and undesirable compounds in plum brandies

This study investigates the effect of double- or single-stage distillation and different alcohol content in 'hearts' (middle fractions) on the distribution of aroma volatiles and undesirable compounds (methanol, hydrocyanic acid, ethyl carbamate) during distillation of plum brandies. Irrespective of the distillation method used, the first fractions ('heads') included mainly aliphatic aldehydes, acetals and esters as well as higher alcohols (1-propanol, 2-methyl-1-propanol, 1-butanol, 2-methyl-1-butanol and 3-methyl-1-butanol). Furfural, 1-hexanol, benzyl alcohol, 2-phenylethanol and ethyl carbamate occurred in relatively high concentrations in the 'tail' fractions. Increasing the concentration of alcohol in the heart fractions from 70 to 90% v/v resulted in a gradual decrease in the concentration of all detected volatile compounds. Compared with single-stage distillation, double distillation produced heart fractions with lower concentration of acetaldehyde and benzaldehyde and with higher contents of furfural and esters, such as isobutyl acetate and isoamyl acetate. There was a statistically significant increase in the amounts of methanol and ethyl carbamate obtained from double distillation compared with similar fractions derived from the single-stage process. However, in all fractions these compounds occurred in concentrations much lower than the limits specified by EU regulations. The heart fraction from the double-stage process with 83% v/v alcohol content received the best scores for aroma and flavour. Copyright (C) 2017 The Institute of Brewing & Distilling