Tannins are organic polyphenolic compounds that occur naturally in things like leaves, wood, nuts and certain fruits. Part of a plant’s defence mechanism, tannins are bitter tasting and astringent – in the natural world, they make things less tasty, and therefore less desirable, to both humans and animals. This allows the plant in question to establish itself and proliferate before someone (or something) gobbles it up.
If a wine is described as having a tannic structure, it will have had some contact with grape skins, seeds and stems during wine-making. Likely too, that it will have spent time aging in wood, for oak is rich in tannin. When it comes to tannins in wine – red wine – it’s a case of balance. Wines that are overly or aggressively tannic will dry your mouth out in a single sip; like you’ve just sucked the sleeve of a velvet smoking jacket. Tannins, you see, have this wonderful ability to dry out proteins – that dry, almost furry feeling in your mouth comes as a direct result of tannins going to work on amino acids in your saliva. Conversely, red wines with lower tannin levels can lack complexity. Since a major part of wine’s intrigue is what happens on your palate when you taste it, a little bit of astringency, a little bit of bitterness and certainly a little bit of ‘furriness’ is no bad thing, especially when you’re pairing red wine with food. It’s easy to counteract (or limit the effect of) tannins on your palate by pairing wines with protein rich foods. Fats also facilitate balancing tannins on the palate. Tannins are essential for a wine that’s intended for the cellar. Wines with no tannins, low tannins, or a ‘soft’ tannin profile will typically not age well at all.
Tannins in white wine are, usually, negligible. With a few notable exceptions (whites that have had extended maceration, and whites aged in wood), white wines are made in a way that limits the transfer of polyphenols from grape skins, seeds and stems to the actual juice.
And so, for a little experiment… cut open a new black tea bag and sprinkle the contents on your tongue. Chew on the dried leaves for a while before spitting it out. Note that furry sensation; that intense dryness and astringency; that bitterness and brownish residue on your tongue and teeth? Tannins!