AGGLOMERATION OF ETHYL-ESTERS IN MODEL SPIRIT SOLUTIONS AND MALT WHISKEYS

Medium- and long-chain ethyl esters were found to have a limited solubility when model spirits and malt distillates were diluted to 230 ml ethanol per litre for sensory analysis. At concentrations above this critical level the concentration of esters in solution remained constant, with the excess esters forming agglomerates. The saturated nature of the solution reduced the volatility of other esters, with a proportion of these compounds being partitioned into the agglomerate. The distribution was dependent on the mole fraction of each ester and its activity coefficient. Dissolution of wood extractives caused a number of changes in the solubility parameters of organic compounds; activity coefficients were increased and both the concentration and activity at which agglomeration occurred were decreased. This resulted in lower solution concentrations with increased concentrations in agglomerates. The reductions in free solution concentration could result in lower headspace concentrations, and thus have a direct effect on the flavour of the matured spirit.