Last time, the topic of dry wines was addressed. It was discussed that 'dry' wines are technically those with no residual sugar. But, more often than not, wine can cause a drying sensation in the mouth that people associate with 'dry' wine. This sensation, generally with red wines, has little to do with residual sugar and is usually associated with tannins.
So, what is tannin? Without getting too technical, tannin is a chemical compound (polyphenol) that occurs naturally in the skin, seeds and stems of grapes. It can also be found in tea leaves, nuts with skins (e.g., almonds and walnuts) and dark chocolate, just to name a few.
Red wines are generally the ones that are highly tannic. This is because the process of making red wine involves leaving the grape skins, seeds and stems in contact with the juice of the grape during fermentation. While most wine makers remove the stems before fermentation, there is still plenty of tannin in the skin and seeds of grapes.
And, tannic compounds also come from wood. So, barrel aging of wines introduces yet another source of tannin.
But wait. With all this talk about tannin, you'd think it's a bad thing. No. Tannin is what gives a wine its complexity and depth of character. Without tannin, the wine would be 'watery,' 'thin' or 'flabby.' And, tannin is a great defender of oxidation. So it defends against the small amounts of oxygen that get introduced in the barrel or bottle that could otherwise spoil the wine.
Finally, and most importantly, tannins don't always produce the dry astringent sensation in the mouth. Tannins are also responsible for producing that wonderful silky smooth sensation in wines. Cabernet Sauvignon is the king of tannin and, when young, can have big tannins that can be described as 'rough' or 'dusty.' But, wines such as Pinot Noir, Merlot, and Zinfandel just naturally have softer, smoother tannins from the start.
To summarize, tannins are a good thing. They have no smell or taste and are responsible for the tremendous complexity and character in red wines. And remember, in wine lingo, a dry wine is one with no residual sugar. But, wines that produce the sensation of dryness in the mouth are due to strong tannins. Cheers!