Changes in wine ethanol content due to evaporation from wine glasses and implications for sensory analysis

Abstract

The relative proportion of water and ethanol present in alcoholic beverages can significantly influence our perception of wine sensory attributes. This study therefore investigated changes in wine ethanol concentration due to evaporation from wine glasses. The ethanol content of commercial wines exposed to ambient conditions whilst in wine glasses was monitored over time. No change in wine ethanol content was observed where glasses were covered with plastic lids, but where glasses were not covered, evaporation had a significant impact on wine ethanol content, with losses from 0.9 to 1.9% alcohol by volume observed for wines that received direct exposure to airflow for 2 hours. Evaporation also resulted in decreases in the concentration of some fermentation volatiles (determined by gas chromatography-mass spectrometry) and a perceptible change in wine aroma. The shape and volume of wine glasses was found to influence evaporation of ethanol. Ethanol evaporated more quickly from wine in certain glasses, which was likely due to increased wine glass opening diameter. The ethanol concentration of wine was found to decrease significantly over time as a consequence of evaporation. The rate of ethanol loss was strongly influenced by exposure to airflow (i.e. from the laboratory air-conditioning unit), together with glass shape and volume. This is the first study to demonstrate the significant potential for ethanol evaporation from wine in wine glasses. Research findings have important implications for the technical evaluation of wine sensory properties; in particular, informal sensory trials and wine show judging, where the use of covers on wine glasses is not standard practice.