What occurs during the oxidation step of maturation?

During the oxidation step of maturation, oxygen interacts with the spirit that is stored in the barrel. This interaction occurs as the spirit breathes through the wood of the barrel, which has been prepared to allow for some level of air exchange. As oxygen enters the barrel, it plays a crucial role in developing the spirit's flavor profile. The presence of oxygen can enhance the formation of complex aromatics, contributing to the overall character of the spirit.

This process not only helps in softening certain harsh compounds but also facilitates chemical reactions that generate a variety of aromatic compounds, enriching the flavor and aroma of the spirit over time. This is an essential part of the maturation process and is integral to producing a refined and complex final product.

In contrast, the other options do not accurately describe the oxidation process. Water evaporation from the barrel is more related to the concentration of flavors but not directly about oxidation. The addition of charcoal is a separate filtration process and does not occur during maturation. Additionally, while the conversion of alcohol into esters is a part of chemical reactions occurring in spirits, it is not directly tied to the oxidation step itself, which emphasizes the role of oxygen in developing aromatics.