Alcohol distillation is a delicate and intricate process, demanding the skills and expertise of an accomplished distiller to successfully complete it. At its heart lies producing a faultless distillate; any flaw could jeopardise both quality and acceptability of your final product.
Distillers employ fractional distillation to separate alcohol from its water components in fermentation mixtures, heating until all of it evaporates and collecting the vapor collected – known as fractional distillation – before cooling it and condensing alcohol from water molecules, thus isolating it from other components of spirit production. If there are unwanted components or ‘congeners’ which don’t evaporate with ethanol evaporating they must be separated out using various techniques (for more details please see Harold McGee’s wonderful book On Food and Cooking).
Ethanol has a lower boiling point than water, yet has higher vapor pressure due to its greater mass and surface tension, causing it to evaporate more quickly than water – leading to its composition being made up primarily of lower order alcohols such as propanol, butanol, and amyl alcohols (collectively known as fusel oils).
These volatile aroma compounds produce an unpleasant and bitter flavor. Their fumes numb the nose of distillers, and unless filtered out they alter the flavor of spirit. Therefore, it is vitally important that tasting vessels be selected with care; an engineered tasting vessel can reduce severe ethanol olfactory numbing while improving aroma definition for those evaluating, judging, rating or distilling spirits.