The Impact of Grape Marc Distillation Process on the Major Volatile Compounds

Abstract

The grape marc represents the product resulted after the pressing of grapes in the wine technology (clusters, skins, seeds and must). It contains many valuable compounds such as: carbohydrates, alcohol, tartaric salts and seed oils. In Romania grape marc is usually used to produce spirit. There were analyzed samples of grape marc spirits from the two stages of distillation process, first and second distillates, as were collected directly from the production process soon after the process ended. The aim of the study it was to evaluate the impact of distillation process on the major volatile compounds in grape marc spirit, resulted after the first and second distillation process. We investigated the ethyl alcohol content by electronic densimetry and 10 major volatile compounds (acetaldehyde, ethyl acetate, methanol, 1-propanol, 1-butanol, 2-butanol, isobutyl alcohol, isoamyl alcohol, amyl active alcohol and furfural) by Gas Chromatography coupled with Flame Ionization Detector. We used reference chemicals to identify these compounds and 3-pentanol as internal standard to quantify the volatiles. This analysis permitted to observe the differences between the two distillates. Acetaldehyde, ethyl acetate, methanol and higher alcohols have smaller amounts in the second distillation step. Furfural registered values below the method detection limit. The factors which differentiate the two samples can be separation of fractions (heads, hearts and tails), temperature applied in the distillation process, quality of raw material and the fermentation process.