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  • Teresa Gomes

All About Tannins: Top 6 Questions Answered

You might have been told that tannins are indispensable in a great red wine. Or you read in a magazine that wine is astringent. And maybe even during a vineyard visit, you were told that some grapes are rich in tannins, but you’re still not sure what they are…

So what are tannins anyway? Want to know the answer? Then, read on.




1) What are tannins?

Tannins are natural compounds scientifically called polyphenols. They are not unique to grapes; they are also present in other plant species in nature. In fact, they appear in the plant as a self-defense mechanism and thus prevent predators from eating their fruits, leaves, and seeds before they fully ripen.

It's no different on the vines. Tannin is one of several phenolic compounds present in grapes.

Approximately 2-7% is present in the stem of the grape bunch, the woody part that supports the berries. And between 0.4 to 3% in the skin of each berry.

Phenolic compounds are important elements of the grape's composition extracted into the wine during vinification. The profile of phenolic compounds in a wine varies greatly depending on the vinification techniques, especially the fermentation time and temperature, the contact time with the skin (maceration), the yeasts and bacteria used, aging (whether in a bottle or wooden barrels) and the use of clarifying agents. All these factors can influence the amount of resveratrol and other phenolic compounds in wine. (Goldberg et al., 1996; Ribéreau-Gayon et al., 1998)

Considering a red wine, it is perhaps one of the most important compounds. The other being the anthocyanins, responsible for the color of the wine, also present in the skin of the grape berry.

Interestingly both tend to soften and become elegant as the wine ages in the bottle.


2) Only red wines have tannins?

During the Sommelier Certification I attended in 2000, this questions was heavily debated. So much so that I still remember.

At that time, tannins were almost exclusive to red wines, as most of the white wines were made through Bica Aberta (see below) method and the rosés were very little coloured or serious.


The exceptions would be some (very few) white wines aged in barrels and whose tannin sensation would be somewhat noticeable in the mouth.


Twenty years later, white wines vinified with the skins (sur lies) and aged in oak, or other woods kinds, are now abundent. So, the answer is no. Tannins can also be present in white and even rosé wines.

“Bica Aberta is the vinification process in which fermentation is carried out separately from the solid parts of the grape. Usually used for whites and some rosés.”

3) What do tannins taste like?

Ripe tannins do not have flavor per se; they generate a feeling of dryness. During the tasting of a wine rich in tannins, your mouth will feel dry, rough, corky mainly on the gums and from the middle to the tip of the tongue.


Describing this sensation with technical tasting terminology, the wine is rough, hard, tannin or astringent.


One of the parameters that’s increasingly considered when deciding when to harvest is phenolic maturation because if the grapes are harvested with green tannins, the wine may have a bitter, herbaceous taste. In other words, the tannins ripen with the grape in the vine, and must be harvested when both are ripe. Amazing, isn't it?


The maturation of the tannins and monitoring the levels of sugars and acidity are the key factors in deciding the ideal time for the harvest. Therefore, the quality of tannins and even the intensity of perception in the mouth are also linked to phenolic maturation.

Therefore, (mature) tannins do not have a flavor. They are perceptible by a tactile sensation in the mouth because the high molecular weight ones are not soluble in water, so they “fight” with our saliva, causing sensations like those described above.

Feel the tannins without drinking wine
Here’s a simple exercise that you can do at home. Make a strong black tea and drink it without adding sugar “et voilá”!
It’s true that tea is also rich in tannins. As are almonds and walnuts when eaten with the skin on. Chocolate rich in cocoa, cinnamon, pomegranate, persimmon, quince, açaí seeds or red beans, among other foods.

Maybe you've lost the desire to drink red wine, but tannins are not the "villain." Remember that tannins, especially in red wines, are very important for the balance of the wine, as are acidity and alcohol.


And yes, they are essential when we talk about aging wines, as they will prevent the wine from oxidizing (antioxidant effect) and the formation of reducing aromas.


Over time in the bottle, the tannins in the wine become elegant.

When they don't cause aggressive dryness in your mouth, you can call them just that - elegant, smooth. You’ll feel their presence but in a pleasant way. They give a soft and velvety texture to the body of the wine. You can also refer to tannins as: ripe, silky, and soft.


4) Do all grape varieties have tannins?

Some varieties are richer in tannins than others, such as Baga, Touriga Nacional, Aragonês, and Alfrocheiro.

In the whites, Arinto, Viosinho and Encruzado. Referring to international varieties, Cabernet Sauvignon and Petit Verdot for instance.


And remember, when drinking these varietal wines (and others) that the winemaking options and wine aging will also condition how much tannins will be present or not in the wine, even in the wines of the aforementioned grape varieties.


5) Does the aging in wood soften the tannins?

When winemaking or wine aging happens in wood (barriques, barrels, etc.) as this is naturally rich in tannins, they will pass into the wine. Although there is oxygenation of the wine during the aging that will soften the wine, it is inevitably joined by the wood's tannins, especially if the barrels are new or with little use.

Oak is so rich in tannins that after cutting the tree, the wood itself spends a few years in the air to lose tannins as well as moisture.

These tannins differ from those of the grapes. They are hydrolysable, that is, soluble in water and alcohol.



With the wine in contact with the barrel wall, the tannins easily pass into the wine in a few months, especially if it is the first use.

Once again, the winemaker will have to make a choice. Most of the time, they intend to use wood to add characteristics of intensity and complexity to the wine, so after three or four uses, the barrels are replaced.

If the winemaker is (can be) patient and wants to use the barrel to soften the tannins in the wine, they will have to opt for a well-used one and wait.


If you’re just starting to taste wines, don't be afraid to take a glass of red wine to your mouth; nowadays most wines have tannins; even if they are creased, they are "rounded."

In addition, the fruity character and alcohol of the wine “tames” the tannins. For the same reason, some people put sugar in their tea or coffee.

6) Is it possible to reduce the sensation of astringency caused by tannins?

Yes, with food! Protein-rich foods such as red meat reduce the sensation of dryness in the mouth. And even more so when the meat is fatty, such as tenderloin, T-bone or rib-eye steaks. At the same time, they enhance the fruity character of the wine. Other options would be duck or lamb.


In this situation, drinking a sip of wine between mouthfuls will also help to cleanse the palate in addition to good digestion.

The temperature at which you drink red wine will also influence the perception of tannins. If you find the wine too astringent for your taste, try to enjoy it at a higher temperature, without exceeding 18ºC.


To learn even more about tannins and Portuguese wines, schedule an online class with me HERE.

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