What is a major challenge in the care of barrels used for sherry aging?

Controlling mold growth is indeed a significant challenge in the care of barrels used for sherry aging. The warm, humid climate of the Jerez region, where sherry is produced, creates an environment conducive to mold development on the exterior of the barrels. Mold can form due to the unique environmental conditions found in the bodegas (warehouses) and can affect the quality of the wine if not managed properly.

Mold may not only impact the aesthetic of the barrels but can also influence the microclimate within the bodega, leading to fluctuations in temperature and humidity that are critical during the aging process. Maintaining the right balance is vital for the development of the wine, as the unique characteristics imparted by the barrels and the interactions between the wine and the wood can be affected if mold is left uncontrolled.

While preventing leakage, managing oak flavor extraction, and ensuring even wood absorption are indeed important considerations in barrel management, they are not as pressing as mold control given the specific conditions under which sherry is aged. Mold can lead to significant quality and production issues, making it a priority in barrel care for sherry aging.