Distillation is the next step to turning fermented mash into something you might enjoy drinking: distillation. While distillation might sound complex and wizard-like, it really just means extracting only the desirable parts of alcohol as liquid vapor while leaving behind any less desirable elements. Heat is then used to break apart and separate its components, known as congeners; these include alcohols, aldehydes, acids and esters whose flavors give spirits their signature taste. Some spirits also have legal requirements regarding minimum or maximum percentages that must be achieved during distillation; other regulations specify this step as part of production.
Here, physics of alcohol-water vapor mixture interactions comes into play. As a general rule, the ratio of alcohol to water in gaseous mixture above liquid is typically less than its ratio in liquid itself – this phenomenon is known as equilibrium relationship.
At first, the ratio is quite stable up until an alcohol concentration of around 95.6 percent; at this point, liquid and vapor mixtures reach an “azeotrope,” rendering fractional distillation useless without other means for separation.
To overcome this obstacle, many large fuel alcohol plants employ vapor separation. This method involves packing a final column with absorbents such as finely ground cornmeal that absorb water, leading to anhydrous (water-free) alcohol being separated from high proof vapors. Unfortunately, however, this process is both costly and energy intensive.
