Effect of Ethanol and Temperature on Partition Coefficients of Ethyl Acetate, Isoamyl Acetate, and Isoamyl Alcohol: Instrumental and Predictive Investigation

Abstract

For alcoholic beverages such as beer, downstream processing for either dealcoholization or off-flavor removal requires both quantitative data and suitable predictive methods. Along with experimental investigations, we use a method initially developed for studying the solubility of gases in two or more miscible liquid solvents to monitor the effect of ethanol on air-water partition coefficients of three major flavors found in beer, namely, isoamyl alcohol, ethyl acetate, and isoamyl acetate. In the ethanol concentration range between 0 and 0.1 mole fraction, a slight, rather linear increase in the Henry's solubility coefficient was observed. This overall behavior can be captured well using Henry coefficients for aqueous binary and ternary systems together with the Wohl expansion for excess Gibbs free energy coupled with the one-parameter Margules equation. Based on the developed model, the Wohl's expansion parameter for ethanol-water is introduced as the solvent-solvent interaction parameter. The van 't Hoff parameters for temperature dependence of Henry coefficients for binary water-flavor solutions are determined in the range of 30 to 60 °C.