HEADSPACE CONCENTRATIONS OF ETHYL-ESTERS AT DIFFERENT ALCOHOLIC STRENGTHS

Ester concentrations in the headspace influence the aroma character of alcoholic drinks. Activity coefficients for esters showed log-linear decreases as ethanol concentration was increased from 17% (v/v), with rates inversely related to ester acid chain length. At concentrations below 17% (v/v) the activity coefficient remained constant. This could be related to structural changes in ethanol/water mixtures. Below 17% (v/v), ethanol forms a monodispersed aqueous solution. Above 17% (v/v ), ethanol molecules cluster to reduce hydrophobic hydration and ester s partition into these ethanol-rich clusters, where the lower ester in terfacial tension reduces the free energy of mixing and hence the acti vity coefficient. The increased solubility of the ester reduced the he adspace concentration of the eaters, and hence total ester content may not be a good indicator of their flavour impact. (C) 1998 SCI.