Question: What substance found in almost all red wines and some white wines adds bitterness and astringency?

Answer: Tannins. While tannins can taste bitter, they help wine age well and are rich in antioxidants that may help reduce cholesterol. Tannins aren't limited to wines though and can be found in foods like walnuts, almonds, dark chocolate, cinnamon, cloves, pomegranates, and grapes. So cheers to the red wines...(and those other foods)!