Have you ever been to a wine tasting or dinner party and heard some blowhard try to befuddle and belittle an enthusiastic however neophyte wine lover by asking can you taste how smooth the tannins are in this [red] wine?
One of the most common misperceptions in the wine world is that you can taste tannin. In fact, tannins are expressed through the mouthfeel of wine. In other words, you perceive tannin through a tactile sensation.
"Tannins, the constellation of phenolic compounds found in grape skins, stems, and seeds and in the wood of barrels," explain celebrity sommelier Rajat Parr and über hip wine writer Jordan Mackay in Secrets of the Sommeliers: How to Think and Drink Like the World's Top Wine Professionals (Ten Speed, 2010), "are the second important contributor to a wine's mouthfeel..." (Acidity is the first.) "Light tannins are typically gentle and flowing on the palate; heavier ones often have a grainy or coarse texture. Some can be so aggressive that they make the mouth pucker. Tannins can almost be perceived to have a flavor profile: some may seem sweet and others bitter."
In purely technical terms, tannins, write the editors of the Oxford Companion to Wine, are a "diverse and complex group of chemical compounds that occur in the bark of many trees and in fruits, including the grape. Strictly speaking, a tannin is a compound that is capable of interacting with proteins and precipitating them; this is the basis of the process of tanning animal hides (hence the name tannin) and is also a process that is believed to be responsible for the sensation of astringency."
What is astringency, you ask?
Parr and Mackay elucidate: "Rajat, a habitual tea drinker, suggests brewing a few cups of tea to gain a rudimentary understanding of the impact of tannins on the mouthfeel and flavor of a beverage. 'Get a green tea or a black tea,' he counsels, 'and brew cups that have steeped for thirty seconds, one minute, three minutes, and five minutes. You can easily taste the differences in astringency.'"
Although tannin can be imparted to wine through the use of wood tannin (new oak barrels or oak chips) or even through the addition of tannin extract (as in the case of one of the worlds most famously tannic wines, Penfolds Grange), most of the world's noble red wines get their tannic "structure" through skin contact, in other words, maceration of the juice and grape skins. The more tannic the grape and the longer the winemaker macerates the juice with skin contact, the more tannic the wine. (White grapes are generally not vininifed with skin contact, but an increasing number of European winemakers have begun to produce "orange wines" made from white grapes that have been macerated with their skins.)
In wines made from particularly tannic grapes like Cabernet Sauvignon, Syrah, Tannat, Nebbiolo, or Xinomavro, the tannic component can often mask the fruit flavors of the wine, especially when it is consumed too early in its evolution. This is one of the reasons that dick-wagging wine collectors will often cry "infanticide!" when wines intended for long-term aging like Bordeaux, Burgundy, Barolo, or Barbaresco (among many others) are opened in their youth (ten to 12 years of age is a good rule of thumb for opening wines like these).
Tannin helps to preserve the wine, and as the wine ages, it will become smoother and gentler, as in the case of the 1974 Barbaresco by Produttori del Barbaresco in the photo above. For the patient wine collector, the balance in astringency and fruit found in certain (not all) aged red wines can deliver the greatest reward (the trick is knowing when to open the wine before its acidity and fruit flavors begin to wane).
Here's my suggestion for learning how tannin affects the mouthfeel and flavor of wine: Buy a bottle of 2007 Barbaresco by Produttori del Barbaresco at the Houston Wine Merchant (for around $40); open the bottle and pour two glasses (one for you and one for your dining companion); put the cork back in the bottle and place the bottle in a cool place, shielded from sunlight; the next night, pour another two glasses, recork and store; repeat on the third night; with every 24-hour cycle, the tannin in the wine will become more mellow, allowing the fruit in the wine to emerge.
One of the things that we love about especially tannic wines is how the tannic structure preserves the wine after being opened and the gustatory joy delivered by the wine's evolution over the course of three or four days or even a week. Last night at dinner, for example, I drank the last glass of inky, chewy Syrah by one of my favorite California producers, Donkey & Goat. The wine had been open for five days and its tannin had mellowed to the point that the wine's umami and dark fruit flavors had emerged in their full glory.
The moral of the story? Good things come to those who wait... and even those who don't wait that long...