Tannins are astringent, furry-tasting, preserving compounds of many, if not most, red wines. They pucker your mouth, have a gritty mouth feel, but are never harmful, for their presence protects and prolongs the shelf life of wines.
Tannins are found in plants as protection from animals and are antioxidants. They enhance flavour and mouth feel by giving wines structure.
When red wines are cellared, tannins agglomerate and fall top the bottom of the bottle. Properly cellared red wines for an appropriately long time taste smoother than those young.
White wines contain very little or no tannins.
Some people are allergic to tannins and get headaches after consuming one or two glasses of young red wines.
Cabernet sauvignon, nebbiolo, and tannat contain high levels of tannins, whereas pinot noir and gamay from Beaujolais less. Sangiovese, the typical grape variety of Tuscany, and many others are less tannic.
Micro-oxygenation during barrel aging reduces tannin content, or at least makes them less aggressive.
Tannins represent a group of chemicals that occur in the bark of many trees and in fruits, including grapes conferring astringency to their taste.
They are derived from flavonoids by condensing together two or more structures of the flavonol types including cathechin and protocyanidins.
Tannins in wine originate in the skins of grapes, stems, seeds, the barrels in which the wine was aged.
If you want to experience the taste of tannins, steep a tea bag several times in hot water.
They are only a few of the constituents that cannot be smelled, only felt, as bitter and mouth puckering.
GA (gallic acid) is used as a measure of tannins in wine. White wines contain an average of 300 milligrams /litre GA, whereas they occur six times more in red wines.
The tannin types and their extraction rates vary considerably with grape variety and winemaking techniques.
If a winemaker decides to separate each grape from the stalk, (a considerably labour-intensive undertaking) and then crush, the resulting wine is likely to be less astringent than those made by bunches crushed, soaked for a long time, fermented at high temperatures, pressed thoroughly and aged in new small barrels.
Excessively high tannin levels can be adjusted by fining with casein, gelatine, or albumin, before bottling, and by cellaring for a long period at approximately 10 – 12 C with high humidity.
If you encounter a very astringent wine, you can mitigate its flavour by pairing it with medium-rare grilled meat or lamb chops.