When is wine stored in barrels exposed most to oxygen?

• A. During fermentation and related tasks
• B. During bottling
• C. During racking, lees stirring, and topping up
• D. During initial fermentation

Answer: (C)

Oxygen exposure in barrel aging is highest when the wine is actively brought into contact with air. Fermentation happens largely without oxygen, so it isn’t the stage of greatest exposure. Racking—the transfer of wine between vessels—momentarily increases the wine’s surface contact with air and can introduce air into the barrel, creating a window of more rapid oxygen uptake. Lees stirring, or batonnage, increases agitation and surface area, allowing dissolved oxygen to enter the wine more readily through the tiny amount of air present and through the exposed surface of the lees. Topping up, while aimed at reducing headspace, involves opening the barrel and adding wine that may carry dissolved oxygen; the process creates a brief moment when oxygen can be introduced into the system. Taken together, these activities are the times when the wine experiences the most oxygen contact in barrel aging.