What type of yeast is primarily involved in biological aging of Sherry?

The primary type of yeast involved in the biological aging of Sherry is Flor yeast. Flor yeast, specifically Saccharomyces cerevisiae, is a unique strain that thrives in the environment of Sherry casks. It forms a protective layer, known as "flor," on the surface of the wine, which helps to prevent oxidation and imparts distinct flavors and aromas. This yeast plays a crucial role in the aging process, especially for styles like Fino and Manzanilla, where a significant amount of biological aging occurs, enhancing the wine's complexity and profile.

Flor yeast contributes to the development of the unique characteristics associated with these types of Sherry, creating fresh, floral, and sometimes nutty notes that are key to their identity. Its presence is essential for the successful aging of Sherry wines in the solera system, as it allows for the development of the specific organoleptic qualities desired in these styles.