What term refers to the product that evaporates from the barrel during bourbon maturation?

The term that refers to the product that evaporates from the barrel during bourbon maturation is "Angel's Share." This phrase captures the phenomenon where a certain amount of the liquid in the barrel evaporates due to the aging process. Various factors, such as temperature and humidity changes, influence how much bourbon is lost during maturation. The remaining bourbon is what makes it to the bottle, while the evaporated portion is poetically referred to as the "Angel's Share," implying that the loss goes to the angels.

In the context of bourbon production, understanding the term "Angel's Share" is essential, as it affects both the concentration of flavors and the overall yield of bourbon from any given barrel. The concept also highlights the unique characteristics of bourbon aging in different environments, such as variations experienced in different seasons or in various geographical locations.