This presentation will discuss the evaporation of pure water and binary and ternary mixtures of ethanol and water containing aroma molecules, focusing on the influence of composition and evaporation geometry on evaporation dynamics and interfacial adsorption-desorption processes. Experiments were conducted in a controlled environment by varying the diffusion pathways in both the bulk solution and the headspace, as well as the evaporation area.
Gravimetric measurements and maximum bubble pressure tensiometry were employed to monitor changes in the weight and composition of the solutions of volatile amphiphiles, as well as the interfacial adsorption-desorption processes, over a timescale of several days. For pure water, molecular flux towards exchange opening between the semi-closed headspace and open air is the rate-limiting step in evaporation. In ethanol–water systems (within a concentration range of 5–80 wt%), the relative and absolute evaporation rates of the components are determined by alcohol concentration, surface-to-volume ratio and liquid-phase diffusion path in a non-trivial way. By adjusting diffusion pathways in the liquid and headspace, the greatest reduction in ethanol concentration in an initially 40 wt% ethanol solution occurs in the system with the smallest surface area — a non-trivial result.
In the ethanol–geraniol mixture, the surface tension remained nearly constant during evaporation, suggesting the presence of a persistent ethanol–geraniol interfacial layer that retards geraniol desorption. The results demonstrate that in mixed solutions of volatile amphiphiles, bulk-phase evaporation is governed by coupled gas-phase transport, liquid-phase diffusion and interfacial kinetics, all of which are modulated by system geometry. These results pave the way for new approaches to studying the release of aroma molecules (e.g. fragrances), where the headspace volume and airflow influence olfactory perception.