Understanding Alcohol Yield in Distillation

Understanding alcohol yield in distillation is central to understanding spirit production. Yeast feed on sugar to produce ethanol, while the remaining liquid contains water as well as various chemicals including acids, aldehydes, esters and congeners – these components give spirits their flavour – both good and bad! Distillers must balance keeping these elements but only in adequate amounts for desired results.

Distillation is used to separate flavor components from water and ethanol by boiling off water through repeated cycles of vaporisation and condensation, with each cycle increasing alcohol concentration while decreasing congener content (see the graphic below).

At first, the lowest boiling-point compounds will be released – these are known as “heads” or ‘foreshots”, and their foul odour and taste isn’t ideal; further down comes more desirable ethanol alcohol vapors that have more desirable qualities which have become known as the ‘heart” of the run; by diverting their path out of the condenser they can be easily separated out and saved for future use.

Distillers aim for an end product that contains a high concentration of ethanol and lower concentrations of other congeners – and that’s exactly why we must understand % Yield. To calculate it, first know your Experimental Value; divide this figure by your Theoretical Value; multiply this resultant figure by 100; then this result will become your %Yield value.