The word tannin is often used and frequently misunderstood. Although the science of tannin is all chemistry and molecules, in this post I will skip the science to tell you the basics of tannin: why it matters and where it comes from.
What are tannins?
Over-steep a cup of black tea and take a sip without milk or sugar. Better yet chew on a grape stem. That bitter, astringent taste followed by the mouth puckering, gum drying sensation is a concentrated example of tannin. Both options sound terribly unpleasant with good reason. Tannin evolved in a variety of plants, leaves and fruit as a defense mechanism. The astringent flavours ward off hungry herbivores. Luckily for us, tannin in wine can be anything but off-putting. In fact, some of the world’s most revered wine is chock full of the stuff.
Why do we need tannins?
Tannin in wine is important for several reasons: it contributes to a full mouthfeel, enables aging, and provides health benefits. Tannins are thought of as the backbone of red wines, providing structure and ageing potential. The structure in tannin creates a full-bodied, mouth-filling sensation that we so often look for in a red wine. This filling sensation is created when tannin molecules bind with proteins in our saliva (more geeked out tannin information here).
Tannins also act as a natural preservative, preventing oxidation and spoiling. As tannins age their chemical makeup changes. These changes produce two effects. First, the once very drying sensations of young tannins become softer and more elegant. Second, some tannin may be converted to tiny crystals that form in the bottom of the bottle. These crystals are harmless, but usually not pleasant to drink so aged wines are sometimes poured into a glass decanter to the point where sediment begins to fall. Tannins are also thought to have a beneficial effect on our vascular system, suppressing arterial hardening (yay!).
Where do tannins come from?
[Editor's Note: Warning! Some nerdy scientific wine stuff ahead...] [Writer's Note: I'm a nerd!]
Tannin in wine comes from two sources. The first source of tannin is from the grape or more specifically the seeds, skins, and stems. As most of a wine’s tannin comes from skin contact, the thickness of a grape’s skin is linked to its tannic potential. Grapes like Cabernet Sauvignon, Nebbiolo and Syrah have thick skins and thus tend to produce more tannic wine. Grapes like Pinot Noir, Gamay and Cabernet Franc have thinner skins and produce lower-tannin wine.
Although grape skin thickness plays a role, winemaking techniques ultimately determine tannin level. For example, white wines are not exposed to grape skin during fermentation so have no tannins and no colour, colour also determined by grape skin contact.
Red wines, by definition have skin contact, if they didn’t they would not be coloured red. The length of time a red wine soaks with the skins (“maceration time”) and the amount of times the skins are stirred in the fermentation tank (“punching down the cap”) impacts the amount of tannin in a wine. Tannin is further impacted by how the grape’s juice is extracted. The juice that flows freely from the tank after fermentation or “free run” contains less tannin than the juice that is pressed from the tanks after free run finishes (press wine). This makes sense, as pressing the wine further crushes the grape skins, concentrating tannin. Sometimes free run and press wine are combined, the free run juice adding bright fruit flavours and the press wine adding tannins, colour and complexity. Other times these wines are not combined and will be produced under different labels, the free run usually higher regarded and higher priced.
The second source of tannin in wine is from oak barrels, newer oak in particular. Remember that tannin occurs naturally in bark, and plants. Oak ageing is the only way a white wine can have tannins. Tannins from oak are usually softer and more easily oxidized than tannins from grapes.
Although tannins are very important to red wine, wines with low or no tannins are not necessarily lower quality and may in fact be more enjoyable in their youth. Wines like Beaujolais (from the Gamay grape) and Pinot Noir can be delicious, and complex without high tannin levels. So what to do with all this new-found tannin knowledge? Drink of course. Notice differences in tannin levels, think about what these differences could be caused by, and most importantly sort out what types of wines you prefer.
Nicole is a wine blogger and all around wine worker bee at Lifford Wine Agency, Ontario’s largest supplier of wine to the province’s hospitality industry and the number one supplier of fine wine to the L.C.B.O. Wine Decanted is a bi-weekly column about wine. You won’t find tasting notes or scores here. Instead she’s taking the hot air out of wine writing and giving us tips for folks who just want to learn more about the good grape.