“Paul, I noticed that you often mention ‘tannins’ in your newsletter. Are tannins what makes a wine taste dry?” E.N., Portland, OR
This is a good question and although the answer is yes, there’s much more here than meets the eye (or the palate, in our case).
In looking at a wine’s overall quality profile, one will find that tannin content is just one of several factors which contribute to a wine’s dryness. One will also find that the function of tannin goes way beyond adding to the dry taste. But let’s back this up for a moment. What exactly are tannins?
Tannins are a group of organic compounds existing in the bark, wood, roots and stems of many plants, and in the skins of grapes. They are important commercially as they are used in the tanning of leather. Although tannins are perhaps the most important component of fine red wines, they have a bitter and astringent taste. When tasting an extremely dry wine, astringency is evident as a coarse or rough feeling and/or a “puckery” sensation on the walls of the mouth.
This is only part of the perception of dryness, since sugar and acid content also have a lot to do with the overall characteristic that we refer to as “dry”. A vintage port, for example, might contain a heap of tannin, but also a lot of residual (unfermented) grape sugar The consequent sweetness would tend to “mask” any astringency. The port would taste sweet. By the same token, a wine could contain very little tannin and still taste dry. Grapeskins, the major source of a wine’s tannin content, are generally not used in the vinification of white wines. Dryness in white wines reflects their high fruit acid content and low residual sugar, no their tannin content.
The bitter taste which tannins can impart (especially noticeable in young red wines) is not normally savored by new wine drinkers. As a wine ages, it casts off a sediment. Tannin forms part of this sediment. A mature red wine has less tannin than a young one. With experience, many consumers do develop an appreciation for the slight bitterness which can be encountered even in a well-aged red. One gauge of the maturity of a wine is its tannin content. A wine, though ten years old, might contain a lot of tannin. Relative to its life cycle, it would still be young (some wines don’t peak until they are 20 or 30 years old!). Tannins act as antioxidants in wines, protecting them against overoxidation during the aging process. Moreover, when tannins themselves oxidize, they can produce desirable flavors. This is why some very old wines are so wonderful.