Measuring Rates of Esterification in Spirits Based on Multiple Variables

  Jordan Spitzer The formation of esters is an essential process in the aging of spirits. The two principal classes of esters, acetate esters and ethyl esters, are enumerated as to their structures, sensory characterizations and aroma thresholds. The formation of acetate esters is inhibited by the time-dependent rise in acetic acid content from wood-based hemicellulose extractions and from oxidation of ethanol, both of which processes require several years in barrel. The formation of ethyl esters is similarly inhibited by the slow oxidation of higher alcohols to their respective fatty acids, which also requires several years in barrel. The dependencies of reaction temperature, % alcohol by volume, and the presence of catalysts on the kinetics and eventual equilibrium ratios of ethyl acetate and its constituents (ethanol and acetic acid) are presented here.