The Tannin Factor

Wine is such a mysterious beverage. We sniff it, quaff it, swizzle it, and then come up with all these wild descriptors: cassis, meadow, leather, mushroom. Where do all these elusive aromas and flavors come from? Partly from the grape, partly from aging in oak, (partly from our imaginations) and partly from tannin.

Tannins are a group of chemicals that occur in the bark of many trees, cinnamon is an example, and in fruits, including grapes. Tannins are also present in black tea, and cause the astringent, drying effect that you experience after several cups of strong tea. You'll also notice a dry, sandpapery effect in your mouth after eating a whole bunch of table grapes. The tannins in grapes are a woody substance in the skin and seeds.

The pulp of a grape is mostly juice, as you can see if you slice a grape open. This is why wine grapes are generally small and round. Table grapes seem to get larger, longer and more seedless every year (and in my opinion, a little more tasteless.) Wine grapes, unattended in rich soil, can also become quite large. I have seen bunches of zinfandel grapes as long as my forearm and as heavy as a small salmon. But this is exactly what winemakers do not want. Smaller grapes have a higher skin-to-juice ratio, resulting in wines with color, flavor and tannin.

Some grapes, like syrah, nebbiolo and cabernet sauvignon have naturally higher levels of tannin than other grapes. Winemaking styles also preserve or delete some of the tannins in wine.

Tannins, which are insignificant in white wines, quite strong in young reds, and softened in older red wines, have a drying effect on the palate. I've often encountered wine tasters who claim that a completely dry wine tastes "sweet" to them. What they are tasting, however, is a dry, fruity wine with very little of the drying astringency contributed by young tannins.

Tannins are derived from flavanoids by condensing together catechin and proanthocyanidins. Catechin, a natural compound used in tanning hides, is also making press in health reports these days as one of nature's compounds responsible for maintaining a healthy heart. Proanthocyanidins simply mean pro (from), cyan (blue), antho (plants); meaning a complex of substances derived from blue fruits like grapes and plums.

White wines are made without much contact between the juice and skins. Without the blue pigments and flavors of red grapes, the skins of white grapes are simply bitter, and are discarded early in the winemaking process. Woody flavors in white wines are generally contributed by oak. Red wines, however, are allowed to ferment for up to ten days with their skins and seeds, sometimes stems as well. In fact, as the skins and seeds float to the top, winemakers and cellarmen make an effort to punch them back down into the wine several times a day; much the same as stirring a slow-cooking pasta sauce.

Tannins play an important role in the aging of wine, particularly red wine, and need careful mastery during wine-making as they can taste bitter and astringent if the fruit is squeezed too hard in the press, or if the skins are left in the juice too long. Handling the skins and seeds during winemaking is one of the most critical steps in optimizing the quality and character of red wine.

Tannins in wine come from both the grapes, and the wood in which it was aged. However, the tannin in wood differs in significant ways from grape tannins. And since wine barrels hold fifty-five gallons or more of wine, the ratio of wine to wood is less and the effect gentler.

Over time, as wines mature in the barrel, and particularly as they age in the bottle, tannins are removed. The tannin molecules agglomerate and polymerize, chaining together to form larger, more complex substances, so that eventually those molecules above a certain size precipitate as sediment and no longer have any bitter or astringent effect on the palate.

Medium-sized polymerized tannins interact with the proteins of taste buds sensitive to bitterness, while larger ones function as tanning agents and a natural preservative. This is why well-made red wines can age for years, while white wines should generally be drunk young.

This is also why it's difficult to properly taste white wines after drinking red wines. The drying effect of tannin results in what we call "palate fatigue." I generally suggest to wine tasters that instead of tasting the entire gamut of white and red wines at several wineries, that they set up a wine "quest" for the weekend, and only taste whites or reds, but not both.

It's also possible, if you are confused about whether you like wines that are sweetish or completely dry, that you prefer a certain level of tannin and oak. There are many levels of tannin structure in wines, in addition to the varying elusive flavors of the grapes. The next time you go wine tasting or buy a new brand of wine, take your time and study its aroma, its flavors, and that leathery, woody, seedy component called tannin.

Comments

[Enobytes]

Great article Mary. I've had consumers describe tannins as "bitty" (bite-y) e.g. "I'm looking for a wine that doesn't give me that "bitty" sensation", as their facial gestures articulate a puckery expression. It's always a fun and informative opportunity to educate consumers on what sensations they are experiencing and to guide them in finding a wine that suits their palate.

Cheers! Pamela

[nolan tew]

am looking to buy 1(one) zinfandel plant for next years season. could u please direct me to an on-line location where i can do this? i consider myself a backyard master gardener with grapes as my 1st love; however retired, i am ordering exotic plants(zinfandel included) to plant in pots in my new rv park location.thank you for your time.

[Mary B.]

Hi, Nolan! You should be able to order single zinfandel vines from Aaron's Nursery. Here's the website: http://www.aaronsfarm.com/category/Grapevines
Let me know if they can't deliver, and I'll try to find another source.