what are tannins in wine

What are tannins in wine?

Learn About Tannins in Wine

What are tannins? It’s a question every wine lover asks sooner or later. 

Not long ago I was asked about what happens to tannins in red wines as they age. The best ad-lib analogy I could come up with at the time was this: They’re like the Rolling Stones—just when you think they’ll soften up, mellow out and fade quietly into the background, they’re back on tour, on stage, commanding attention and prancing on your palate.

I am reminded of the staying power of tannins whenever I taste red wines, irrespective of their age. Infant red wines are predictably tannic because tannins come from grape skins (and seeds and occasionally stems), which also capture the varietal flavor of a grape. But even in mature wines, tannins rarely melt away like butter.

I like tannins. Aside from flavor, they provide structure, texture and mouthfeel. You can actually chew on the tannins. But a little tannin goes a long way, and when I drink older wines I prefer the ones in which fruit survives and is the focal point rather than the tannins. Usually, it’s the other way around.

As it is, tannin types and their presence in wine vary considerably by varietal. Some wines that are lighter in color can be quite tannic, especially if they’re also high in acidity or alcohol, which magnifies tannin levels. Nebbiolo, the great grape of Barolo and Barbaresco, and Pinot Noir are two grapes that can render surprisingly tannic wines, even when their colors are not saturated.

What are Tannins?

The dictionary isn’t much help. Here is the definition:

tan·nin
noun

Tannin in Oak

Tannins are also leached into wine from oak; and the newer the barrels, the stronger the presence, in mouthfeel and flavor.
The major threat tannins pose, though, is bitterness, or astringency. That’s why so much attention is paid to tannin management, starting in the vineyard and extending through fermentation. Harvest dates are crucial. Picking underripe grapes gives tannins a green, herbal edge; overripe grapes can taste raisiny or pruny.

Winemakers are constantly rethinking tannins and experimenting with new methods of taming them. Tasting grapes (and chewing the skins and seeds) is the current rage. That gives an indication of a grape’s physiological ripeness and tannins.

Fermentation methods also influence tannic strength. Some winemakers prefer shorter, weeklong fermentations, with an emphasis on extracting color and flavor (and some even barrel-ferment the final phase). Others stretch vinification for weeks, even months, with the goal of softening the tannins and culling flavor. Some even add tannin powder to buff up their wines.

Effect of Age on Tannin

Because tannins act as a preservative, they are one of the most important factors in determining the longevity of red wines. Their enduring presence is also one revelation that comes from drinking older red wines, great or otherwise.

When you taste a mature wine that has evolved gracefully and that has maintained a mix of youthful flavors while developing the subtle nuances that come with time, you can be assured that it began life in near-perfect balance (and that it was impeccably cellared with a faultless cork). That’s why winemakers ultimately define great wines by their balance. Foremost among the factors determining balance is the structure and amount of tannins.

Concentration, richness, acidity and alcohol (and sugar in sweet wines), among other factors, also play vital roles in a wine’s ageworthiness. Moreover, defining what constitutes a mature wine differs for each of us. I’ve savored ancient Bordeaux, Brunello di Montalcino, Sauternes and Vintage Port and listened to experts discuss these century-old wines as if they grew up as childhood buddies who are still close friends.

Century Old Wines

The last time I tried a pair of 1870 Bordeaux, from Châteaus Lafite Rothschild and Latour, both exhibited the faded, wilted rose petal and dried-fruit scents of their age. I admired the longevity of these wines, but was amazed by how persistent the tannins remained. Clearly, these wines aged beautifully because of their tannins and balance. But more often, older wines dry out and lose their fruit vitality. Then tannins are all that remains.

After years of tasting, reviewing and drinking wines, I’ve come to a greater appreciation of texture and pleasure. More often than not, the two go hand in hand. Central to that equation is the balance of tannins.

You rarely have to look hard to find tannins. They hang around like the Stones. No one knows when they’ll fade away.


The Science of Red Wine

The science of flavor is still in its infancy. Only a handful of the trace elements of wine have been studied, and many flavor compounds -in different proportions-can give distinctly different flavors.

Esters

The biggest contributor to flavor is yeast. It is the fermentation process that truly gives a wine its flavors. If conditions are right, acids will combine with alcohol or tannin in the grape to form an ester. These are the flavor compounds in wine.

To rephrase: Esters are the result of a reaction between the grape skins, acids, and yeast during fermentation.

When you say a red wine has  has a berry-like character, or smells like roses, it is because the esters in the wine are mimicking the smell of berries. Please also note that – as we have discussed – flavors such as apple and pear can also come from the acids (tartaric and malic) in wine.

These esters can work together to create new flavors. For example, ethyl butyrate (from the grape) with diacetyl (malolactic fermentation) yields a butterscotch attribute in a wine. Another  example is ß-damascenone which gives an apple, fruity flavor and will elevate other fruity notes (such as a-ionone) in a wine.

Sometimes the esters will clash: a high concentration of methionol will blunt most fruit flavors. Polyphenols
One of the most important flavor elements in wine, especially red wine. Polyphenol translates to  “many phenols” or, more prosaically, “lots of aromatic stuff jammed together”. They are also responsible for the coloring of some plants—for example, the color of leaves in the autumn… and the skin color of red wine grapes.

Tannins

Research indicates that a class of polyphenols has antioxidant characteristics with potential health benefits. These polyphenol antioxidants may reduce the risk of cardiovascular disease and cancer. High levels of polyphenols can generally be found in fruit skins, with some of the highest percentages in grape, apple, and orange skins.

This class of polyphenols is called tannin, which give red wines their astringency and bitter taste. Well, actually they are condensed tannin (anthocyanins) but that really isn’t that important. What is important is that tannins are not water-soluble and will precipitate protein.

To rephrase: eventually the red and bitter stuff in wine will fall to the bottom of the bottle, turning the wine from ruby-red to brick colored… and that is why people age wines! FYI: Tannins are an important ingredient in the process of tanning leather. Oak bark has traditionally been the primary source of tannery tannin, though synthetic tanning agents are also in use today.

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