What does "tannin" refer to in wine?

Tannin refers specifically to astringent compounds that are naturally found in grape skins, seeds, and stems. These compounds are polyphenols and play a significant role in the structure and aging potential of wine. Tannins contribute to the mouthfeel of the wine, often imparting a drying sensation, which is particularly prominent in red wines that have spent time in contact with grape skins during fermentation.

Their presence also serves to contribute to a wine's complexity and can compliment its overall balance. Tannins are an essential component in the aging process, as they can soften and develop over time, allowing the wine to mature gracefully. Additionally, they have antioxidant properties, which play a role in preserving wine.

The other options do not accurately describe what tannins are. For instance, tannins are not compounds that enhance sweetness and flavor, nor are they preservatives used in winemaking or flavoring agents added to wines. Understanding tannins is crucial for appreciating the texture and aging potential of wines, especially for those interested in wine tasting or studying oenology.