Monitoring of Carboxylic Acids by In-Line Conductivity Measurement to Determine Optimum Distillation Strategy for Distilling Apple Spirits

Abstract

Using a novel in-line measurement technique for monitoring the distillate conductivity of apple spirits, the authors demonstrated that a more economic strategy of running a batch column still providing lower heating and cooling energy was able to shift higher levels of carboxylic acids more toward the cut point of tails. By means of more aggressive heating and cooling, the relative volatility of tail congeners was increased, enabling them to enter the condenser already at the beginning of the distillation. Especially during column distillation, reflux rates can heavily impact the transition of less volatile congeners into the product contributing either to an unclean taste when too enriched or to a lack of aroma intensity when too depleted. It was shown that with the selected strategies, the risk of depletion of aroma compounds is higher with increased ethanol fortification and unclean taste can easily be avoided even if higher levels of carboxylic acids are present, especially when the cut of the tail fraction is done appropriately using the described conductivity method.