Tannins: What Are They and What Is Their Role in Wine?

Tannins – soft tannins, firm tannins, round tannins. What exactly are these mysterious, elusive elements you’re always reading about in wine reviews and ratings?  Simply put, tannins are chemical compounds – polyphenols, to be exact – that are found primarily in red grape skins, seeds and stems, and to a lesser extent in oak casks.  Their particular characteristics in wine vary according to the grape varietal and the vinification process.  But how are they actually “expressed” in the wine and what are we looking for when sampling a wine?  The best explanation I’ve found on this subject was posted in a weekly e-mail I receive from “The Juice” which lists wine tasting events in the area and always includes a few factoids about wines from acknowledged experts.  So here we have it:

Explaining tannins in simple terms is rather challenging since they are chemical compounds which have long been studied and analyzed by scientists. Here's my best effort...Tannins come primarily from the grapes - skins, seeds and stems - and, to a lesser degree, from wood barrels. They are associated mainly with red wines, since the juice of dark-skinned grapes is macerated with their skins (and sometimes, the stems). The juice also takes on its red coloring from the skins, with very few exceptions; in fact, tannin and color are linked. So, for this reason, white wines rarely have any detectable tannin, and roses may contain a negligible level. In terms of taste, tannins are best understood as drying, rough coating on the tongue comparable to a strong cup of tea. Not all red wines, or even the majority, impart that astringent sensation. Tannin content differs according to the grape variety and its ripeness. Moreover, the entire winemaking process is controlled to minimize what can be, for many people, an unpleasant and even bitter taste. On the other hand, the great reds - the best Cabernets, Bordeaux, Brunello, Barolo, and so on - do often contain high tannin levels. This can make them challenging to enjoy when first released. However, their tannins allow them to age for many years in bottle. With time, the tannins combine with the coloring matter and "fall out" of the wine, creating sediment. This also explains the fact that old red wines are paler than they were when first bottled, and why they are smooth and silky.

-Roger C. Bohmrich

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