If you love wine, you’ve probably already noticed it has a sneaky way of lingering in your mouth long after you’ve enjoyed it. Ever observed how your teeth look a bit purple after your glass of cabernet? This is thanks to a set of bitter astringent compounds known as tannins. Tannins can be found in foods such as grapes, cacao, cranberry, and tea. But why do they leave behind such annoying mementos on your teeth? Keep reading to understand how tannins take their toll!