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The question: What are tannins? Do all wines have tannins, and are they good or bad?

Tthe answer: They're astringent, sometimes furry-tasting compounds found mainly in red wines. They're never a bad thing where quality is concerned. In fact, some of the greatest, most cellar-worthy wines are strongly tannic. But like the bristly texture of a wool sweater, they can bother some consumers.

Naturally produced by plants, tannins get into the juice by way of grape skins, seeds and stems. They can also come from contact with oak barrels, because there are tannins in wood. If you drink white exclusively, you need not worry. Virtually all juice destined for white wine is drawn off the skins (and seeds and stems) prior to fermentation, and most whites spend little, if any, time in barrel.

On the plus side, tannins enhance flavour by imparting a sense of structure to the wine. Think of a frozen lemon slush versus watery lemonade, or the pulp in orange juice versus the pulp-free stuff you can now buy. Depending on winemaking practices, tannins can have either a raspy texture or a more polished, creamy feel.

Tannins also act as antioxidants, another good thing. They help preserve wine from the ravages of air, and that's the key reason reds tend to cellar better than whites. As wine ages in bottle, the tannins soften. Old reds tend to be less harsh than young ones.

On the downside, tannins aggravate some people because of that sometimes harsh astringency. The mouth-parching quality you get from strong black tea and walnuts is tannins at work. In the case of wine, you can think of tannins as the opposite of acidity; tannins stick to the gums and make you pucker, while acidity makes the mouth water.

Worse, tannins are purported to cause headaches in a small minority of people. The science is sketchy, though, and if you feel no pain consuming tea or walnuts, you're probably not sensitive to tannins. Besides, there are bigger culprits where wine headaches are the issue, notably substances called amines, which are also naturally found in wine. Many people also simply are allergic to alcohol and may not know it.

Even if you're a red-wine drinker, you can curb your tannin exposure, assuming you'd want to. Some red grapes contain more than others. Cabernet sauvignon and nebbiolo (of Barolo fame) are particularly tannic. Tempranillo (of Rioja fame) and sangiovese (the main grape of Chianti) are only moderately tannic, while gamay, the red grape of Beaujolais, and pinot noir tend to be on the tamer side.

That said, it's become a fashion among many producers to soften tannins using a variety of winemaking tricks. Harvesting later in the season can yield riper, less aggressive tannins, for example. And there's a fancy technique, first introduced about 20 years ago, called micro-oxygenation, which rounds out the angular texture with controlled exposure to air during fermentation or maturation, before the wine is bottled.

If it's simply the raspy, furry sensation you want to avoid, try pairing your young red with steak, lamb or cheese. Fats counteract astringency. That's one reason people take their tea with cream even if they're not aware of the science. Cream softens the rough edges. I, for one, have never been a cream man. I'd rather tenderize my tea with a juicy rib-eye.

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E-mail your wine and spirits questions to Beppi Crosariol. Look for answers to select questions to appear in the Wine & Spirits newsletter and on The Globe and Mail website.