Alcohol distillation is where flavors are created and separated. A fermented liquid known as wash contains mostly water and alcohol (ethanol), while the remaining 25% comprises organic chemical compounds like aldehydes, esters and acids; collectively known as congeners which contribute both positive and negative flavor notes to alcohol beverages.
Distillation involves heating liquid to turn it into gas, which is then passed along to a condenser to be condensed back into liquid form. As it passes through this process, its ratio of components A to components B in its vapor changes as more flavor compounds emerge; early stages see mostly heads (lower boiling point, highly volatile) and tails (higher boiling point, less volatile), either discarded or collected depending on what spirit being made.
As the vapor continues to move down the column, it becomes concentrated into hearts as more low-boiling alcohols collect at its center. This heart is responsible for creating that unique fruity or floral taste you find when sipping on spirits such as gin or whiskey.
As hearts continue to collect more fusel alcohols, unpleasant aromas and flavors will develop in them; therefore, distillers will make cuts and divert that vapor flow to another container – often times, this results in tails which you might find in rum, but depending on what spirit is being produced it might benefit from early heads in their heart cuts or late tails in its hearts.
