Tannins: What are they?
Take a sip of strong black tea, and notice that puckery sensation as it coats your mouth with an astringent fuzziness.
Now take a taste of a young Cabernet Sauvignon, and chances are you'll feel a similar sensation.
What you're tasting is tannin (tannic acid), a natural chemical that's sometimes found in tree bark, wood, and the skins, seeds and stems of some fruits - in particular some red wine grapes.
Tannins are used to "tan" animal hides to turn them into leather, and that's actually the process you feel when the tannins in tea or wine start to work on the proteins inside your mouth. Think about that the next time you enjoy a youthful Cabernet!
Tannins in wine come primarily from the grape, although aging wine in oak barrels can also impart a dose of the puckery stuff.
A healthy dose of tannins in a young wine can make it less than a pleasure to drink, and for this reason, certain wines - in particular red Bordeaux and other young Cabernet Sauvignons, the Nebbiolo-based reds of Northwestern Italy, and such less-widely known wines as the Tannat of Madiran - are customarily held in the wine cellar until they mature. During the maturation process, the tannins polymerize (combine into longer-chain molecules), and as a result of this process, the wine develops a bit of sediment in the bottle as its flavor evolves from harsh and astringent to mellow and complex. Tannins also act as antioxidants, naturally preserving the wine during its maturing years.
Not all tannic wines evolve into stylish maturity, however. If a wine is merely tannic without fruit in its youth, it isn't likely to become a thing of beauty with age. Balance is the key.
Finally, if you must "rob the cradle," as wine enthusiasts say of drinking an ageworthy wine before its time, this is the one case in which "breathing" - or better yet, decanting your wine with lots of splashing to mix it with air as you pour - may help soften its rough edges a bit. And serving a youthfully tannic wine with rare red meat will also go a long way to ameliorate that rough tannic astringency.