A winemaker who does not completely fill a barrel may expect which tertiary characteristic in their fortified wine?

When a winemaker does not completely fill a barrel, it creates more surface area of the wine that is exposed to oxygen. This interaction with oxygen is crucial in developing tertiary characteristics during the aging process. Tertiary flavors are complex and often include notes like toffee, nuts, and caramel, which emerge as the wine undergoes oxidative aging.

The presence of oxygen facilitates various chemical reactions that enhance the complexity of the wine, resulting in these rich and nuanced flavors. This contrasts with wines that are completely filled, where the lack of oxygen can preserve more primary and fruity characteristics, keeping the wine fresher and potentially more introverted in flavor profile.

In this context, it is clear why the expected outcome of not fully filling the barrel leads to pronounced tertiary characters like toffee, nuts, and caramel, showcasing the influence of oxygen on the wine's aging process and flavor development.