Tannins. What are they? Where do they come from? Who's peach is this, can I have it? It's not labeled. But then, how do you label a peach? These are just some of the questions you might have.
Tannins are molecules that taste bitter and cause dryness in the mouth. But what seems like bad-tasting dork-science is actually a crucial part of wine, especially if it's meant to age. And what were once thought to be nutritionally neutral at best are now known to be good for our health. So bring on the dark chocolate, pair it with a nice red wine, and read on.
Tannins come into wine a couple different ways. First, grape skins have tannins. Since red wine is red because of skin contact, it generally has more tannins than white. The amount of tannins is influenced by the thickness of the skin and the time spent in contact with it. Cabernet Sauvignon and Syrah, for example, are thick skinned grapes, so they tend to yield tannic wines. Because the skins contain aromatics, sometimes winemakers will do a cold soak for whites. This means they allow the wine to spend some time in contact with the skins quickly, just to extract a little flavor. This will up the astringency (dry mouth factor, and how tannins are referred to in white wines). Winemakers will taste grapes for their "physiological ripeness" which is, in part, a judgement of their level of tannin (as opposed to their physical ripeness, which is just how ripe the fruit is).
Another place we get tannins is from wood. So an oak-aged Cabernet is going to be crazy tannic, and an oaked Chardonnay may have more tannins than an unoaked or lightly oaked Pinot Noir, a thin-skinned grape. Tannins help a wine age, so oak is often used for this purpose. This is also why red wines age best.
More bonuses? While tannins give headaches to some people, they improve vascular health in everyone. Antioxidants in red wine have also been shown to decrease the risk of cancer.
But sometimes tannins can be a bit much, their texture getting in the way of the wine's flavor. This is when we decant wines. If a wine is meant to be aged and we open it early, or just has too many tannins for our liking, we can speed up the aging process by pouring it out of the bottle and letting it relax for a spell. As the wine sits, the tannins link up and sink to the bottom of the vessel. Then they're not so strong. Most wines, however, do not need to be decanted, and contact with oxygen at room temperature will cause aromatics to release, making the wine blander than it ought to be. So don't decant unless the tannins are really getting on your nerves.
Fat softens tannins, which is why we serve red meats with tannic wines like Cabernet and Syrah. But tannins combined with fish oils will taste metallic, while tannins plus another bitter element like heirloom lettuces will create an overwhelmingly bitter sensation. If you like your big reds, make sure you give them a bold meal so they can be at their best.