What specific aging characteristic is used to define "Fino" Sherries?

The defining characteristic of "Fino" Sherries is the aging process that occurs under a layer of yeast known as flor. This flor layer protects the wine from oxidation while also imparting unique flavors and characteristics. For a Sherry to be classified as Fino, it must age strictly under this flor for a minimum of five years. This specific aging environment results in Fino Sherries being pale in color, dry, and having a distinctive briny, nutty, and floral flavor profile.

In contrast, other aging processes mentioned do not define Fino specifically. Aging in oak barrels for just one year may apply to various types of Sherries, but it does not meet the requirement for Fino. Aging without exposure to oxygen is typically associated with styles of wines that are in contact with air, like Oloroso, which is the opposite of the protected aging that Fino undergoes. Aging with significant residual sugar content is more representative of styles like Pedro Ximénez or Cream Sherries, which are sweet and do not reflect the dry nature of Fino.