esters are compounds produced by the chemical reaction between acids and alcohol. In wine and spirit production, they occur mainly as a result of fermentation and aging in a process called esterification. Esters formed during fermentation are influenced by many factors, including base ingredient (grain, fruit, molasses, etc.), fermentation temperature and length, yeast strain(s) used, climate, and other factors, and they can be classified into two groups: acetate esters (acetate plus alcohol) and ethyl esters (ethanol plus fatty acid).
A distilled spirit typically contains hundreds of esters in its makeup, which help create its aroma. The most abundant esters include ethyl hexanoate, with an aroma commonly described as apple, and ethyl acetate, which can contribute both fruity and nail-polish aromas. Other examples of esters and their aromas include ethyl lactate (butter and cream), ethyl cinnamate (cinnamon), isoamyl acetate (banana and pear), and isobutyl acetate (cherry and berries). See aroma.
Many of the lighter esters from fermentation are removed during distillation. The amount of reflux and the size of the cuts made during distillation will affect the amount of esters left in the resulting spirit, as does the acidity of the type of alcohol; highly acidified cognac, bourbon, and many rums are typically high in esters. See reflux and cut.
Barrel aging also contributes esters, transforming acids into simple esters and simple fruity esters into those with notes that include honey and spice. The spicey and cinnamony ethyl ferrulate is a typical result of barrel aging. Generally speaking, the longer a spirit is in a barrel, the more esters it will have.
See also fermentation and yeast.
Fromm, James Richard. “Introduction to Esters.” http://www.3rd1000.com/chem301/chem301v.htm (accessed March 3, 2021).
By: Jack Robertiello