Which process has the largest impact on the flavor profile of bourbon?

Barrel aging has the largest impact on the flavor profile of bourbon due to several key factors associated with the interaction between the spirit and the wooden barrel. During aging, bourbon undergoes a chemical transformation as it absorbs compounds from the charred oak barrels. The extraction of flavors like vanilla, caramel, and spice occurs primarily during this maturation process.

The length of time the bourbon spends in the barrel significantly affects the depth and complexity of its flavor profile. The interaction with the wood mellows the spirit and allows for the development of additional nuanced flavors as the bourbon breathes in and out of the barrel due to changes in temperature and humidity.

Moreover, the char on the interior of the barrel caramelizes the sugars from the wood, contributing to the sweetness and complexity of the bourbon. This process of aging and the specific conditions under which it takes place (environment, barrel treatment, etc.) are often what distinguish one bourbon from another, making barrel aging a crucial factor in determining the final profile of the spirit.