What risk is associated with a cork hardening due to refrigeration?

A cork hardening due to refrigeration poses a significant risk because it can compromise the seal of the wine container. When a cork becomes hardened, it may not fit snugly against the neck of the bottle, which can allow air to enter. The exposure to air can lead to oxidation of the wine, adversely affecting its flavor and aroma. This is particularly important for wines that age over time, as they are sensitive to oxygen exposure, and thus maintaining an airtight seal is crucial for preserving their quality.

In contrast, other options do not accurately represent the effects of cork hardening. The wine becoming sparkling is not a direct consequence of cork hardening. Similarly, while a fragile cork could potentially break, the specific scenario of hardening doesn’t inherently lead to fragility or breakage over time. Finally, the notion that the seal would improve contradicts the reality that a hardened cork will likely result in a compromised seal rather than an enhancement.