What Are Tannins?

You know the feeling - drinking a glass of red wine and then it feels as if fur with bitter notes is spreading across your mouth. This is due to the tannins in the wine. But what exactly are these tannins?

• Vegetable elements in the grape seeds, stem and skin
• Have no taste of their own, but leave a bitter note
• Over 30 different tannins
• Add complexity and ageing potential to the wine

What are tannins?

Tannins naturally occur in various plants (secondary plant substances) and can be found in tea, nuts, cocoa or grapes. Tannins are found in seeds, stalks and especially in the skin, and are significantly more concentrated in red grapes than white. They protect the fruit from predators and, thanks to their antiseptic effect, from putrefactive bacteria.

Tannins don't really have a flavour of their own, but may leave a very slightly tart, bitter note and react with mucous membranes in the mouth, creating a furry texture. In other words, they're astringent.

How tannins get into wine

White wine contains very few tannins. In contrast, red wine gains flavour complexity through tannins. Tannins are therefore of great importance for the quality of red wine. The structure of the tannins is also important because there are over 30 different types.

• Mash fermentation

Tannins get into red wine through mash fermentation. The first fermentation takes place in contact with the skins of the grapes - tannins are extracted from the skin and ensure, among other things, a deep red to red-brown colour. The amount of tannic acid depends on the duration of the mash fermentation or the length of the maceration, as well as the temperature during the process. The higher the temperature, the easier it is for tannins to be absorbed in the wine from the skin. The grape varietal also has an influence on the tannin content. Cabernet Sauvignon, Syrah, Tannat or Sangiovese, for example, have a higher tannin content than Pinot Noir.

The quality of tannins is related to the degree of ripeness. It's possible for the sugar content of the fruit to be very high and the tannins to remain unripe. The state of ripeness is easily checked by regularly tasting the grapes.

• Other ways tannins migrate into wine

Ageing in oak barrels (barriques) also releases tannins. The following applies: The newer or the less used the wooden barrel, the more tannins get into the wine. Even natural cork contains tannins. However, the amounts that corks release into wine are very small and therefore insignificant in terms of taste. It's also possible to add tannins to wine as fining agents. This ensures that the protein separates out and the wine does not become cloudy.

Why do we need tannins?

1. Flavour

Tannins provide characteristic and unique wine aromas and veritable taste explosions. The slightly tart notes add complexity and a full-bodied structure. Tannins hold the wine together so it doesn't become monotonous or flat.

2. Impact on texture

Another effect of tannins is the influence on the texture of the wine. Tannins react with mucous membranes in the mouth and trigger impressions on the tongue, tasting furry, velvety or dull.

3. Shelf Life / Storage Potential

A high tannin content also makes the wine more likely to age well. Tannins bind oxygen and prevent both premature oxidation and aromas from evaporating early.

4. Colour

Tannins help stabilize the colour of red wine by binding with pigments and protecting them. However, the depth of a wine’s colour mainly depends on the grape variety and winemaking process, while clarity is usually achieved through filtration and fining—during which tannins are typically reduced rather than added.

Photo Credits: James Doak Photography