What is a tannin? If you have been around wines for a little while, you must have heard of something called a tannin. From Google:
tan·ninˈtanən/nounplural noun: tannins
a yellowish or brownish bitter-tasting organic substance present in some galls, barks, and other plant tissues, consisting of derivatives of gallic acid, used in leather production and ink manufacture.
Yummy stuff. And actually it really isn’t so bad since you’ve probably tried a wine with tannins before. That “dry” feeling you get in your mouth that might make you pucker, those are tannins at work. The more dry your mouth feels, the more tannins there are in the wine. An example is the feeling that you get when you drink a strong black tea that is steeped for too long, there are tannins in black tea.
So where do they come from?
Tannins actually occur naturally inside the grape skins, seeds (or pips), and stems. Science calls tannins by another name: polyphenols. Polyphens are released from skins, seeds, and stems when they are soaking (after being pressed). Since red wines are fermented with their skins and seeds, there are more tannins in red. The skins also give the red wine its redness.
Tannins are natural antioxidants that protect the wine and they also have health benefits for humans too! This is also another reason why reds can be cellared better than whites. They have more tannins. One downside, however, is that some humans report getting headaches from tannins.
If you want to go out and do a tannin sampling (because what could be more fun than that?), Cabernet Sauvignon is an example of a wine that is high in tannins. Tempranillo and Sangiovese are wines that are moderately high in tannins. On the other side of the scale with reds, Zinfandel, Pinot Noir, and Merlot are examples of wines that are low in tannins.