Have you ever been on a distillery tour and the guide discusses the outcomes of the distillation process and starts dropping the words heads, hearts, and tails? Ever wonder how your bourbon tastes like, well, bourbon, and not ethanol? After all, the cooking process for bourbon isn’t a lot different than the cooking and distillation process to make ethanol to power your car.
The liquid produced from grain fermentation contains many chemical compounds - some undesirable, some downright deadly. The distillation process separates these compounds as each has a different boiling (i.e. evaporation) point. A good distillation process will remove the unwanted components and leave the desirable/drinkable alcohol to bottle as white dog/moonshine or to age over time in a barrel.
Heads are toxic and evaporate first. The hearts are the drinkable liquid and follow next. These are sometimes referred to as low-wine. The tails evaporate last. Some of the aromatics found here are actually desirable, and select tails may be condensed and re-distilled in a second still into high-wine.
Tails
Furfural: Almond-scented colorless liquid that darkens when exposed to air, and also one of the aromatic components of vanilla, flowers, and beans. Used as a chemical solvent and, oddly enough, in many processed foods.
Amyl Alcohol: An industrial solvent with the scent of artificial bananas or Band-Aids. Used to make amyl acetate which is used as a flavoring agent to make foods taste like bananas or apples.
Acetic Acid: This liquid smells like vinegar because it is vinegar. Used in salad dressings, pickling agents and cleaning products.
Butyl Alcohol: Liquid with a lightly sweet scent that is used as a base for perfumes and paint thinner.
Water: No explanation needed.
Propyl Alcohol: A slightly floral or medicinal scented liquid used as a solvent in cosmetics and in the manufacture of lacquers.
Hearts
Ethyl Alcohol: This is white dog - the goal of the entire process. Depending on the grains utilized, this can be aged to become a whiskey, bourbon, rye, or other whiskey. At a higher proof, it can be used as industrial-grade alcohol, used in a variety of manufacturing processes. During World War II, U.S. distilleries produced millions of gallons of this to make synthetic rubber for tires as well as explosives for bombs and artillery shells.
Heads
Ethyl Acetate: A very-sharp, eye-watering scented liquid. Used to kill bugs in jars and traps. Also, oddly, used to decaffeinate coffee.
Methanol: A devilish liquid that has a sweet alcohol odor, but is toxic and causes blindness if consumed. Used as an industrial solvent in the manufacture of resins. At one time, this was made from wood, leading to the phrase wood alcohol.
Acetone: You’ll recognize this one. Yep, the same bottle in your cabinet to remove nail polish. Also used as a solvent in manufacturing plastics.
Acetaldehyde: A highly flammable liquid with the odor of green apples or grass. Can be used as a solid fuel in portable stoves or to repel slugs from your garden.
There you have it. You now have an idea where your decaf coffee, paint thinner, plastic, and bourbon come from. Hats off to our distillery workers that keep allow us to safely sip.