What does "biological aging" refer to in Sherry production?

Biological aging refers to the process where Sherry wine develops in the presence of flor yeast, a layer of yeast that forms on the surface of the wine in cask. This yeast plays a crucial role in the aging process, as it consumes oxygen and protects the wine from oxidation, allowing for the development of unique flavors and aromas. During this period, the wine undergoes a transformation that enhances its characteristics, including a distinctive nutty, briny profile often associated with biologically aged Sherries, such as Fino and Manzanilla. The presence of flor not only helps to preserve the wine but also contributes complexity and a fresh quality that is highly desired in these styles of Sherry. Understanding this process is key to appreciating the distinct styles and qualities of Sherry wines.