Some sources define tannin as "an astringent and bitter plant polyphenol compound that binds and precipitates proteins and various other organic compounds, including amino acids and alkaloids".

Tannin is a polyphenol compound, and the tannins in red wine mainly come from grape skins and seeds. The bitterness and astringency in red wine come from the role of tannins, and red wine with high tannin content is more suitable for aging.

Tannins in the stems, seeds and skins of grapes are the main reason for the aging ability of red wine. Tannins are astringents found in plants and are responsible for the gritty texture in red wine. They have no flavor or aroma, but can be experienced as drying.

The word tannin comes from the use of this compound to "tan" leather. That's why when you drink a high-tannin wine without food, your tongue feels a bit like leather.

Extended information:

Drinking wine with protein-based foods can reduce the wine's Bitterness

The fact that tannins interact with and precipitate proteins is the key to understanding tannins. When tannins come into contact with proteins, they bind together and sink to the bottom of any container.

This removes the proteins and tannins from the wine. Too much protein in a wine can lead to fuzziness. However, due to the presence of tannins during fermentation, most of the proteins precipitate out.

The biggest impact of this interaction comes from drinking red wine. Take a sip of red wine without eating any food and your tongue will feel dry. This is because the tannins in the wine bind to the proteins in the saliva.

It's this settling effect that makes red wine go very well with high-protein foods like steak and cheese. The tannins bind to the excess protein in our mouths, making the wine easier to drink in our mouths.

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