Tannins are compounds found in the grape skin, pips and stem. They are released into wine during the winemaking process that sees the grape juice fermenting in contact with the crushed skins. Skin contact is rare in making white wine, as the aim is to avoid too much leaching of tannin and colour compounds from the skin. Thus, we usually associate tannins with red wines.
Tannins act as preservatives in red wines and facilitate the slow bottle ageing process. This sees both flavour and tannin compounds (collectively called phenolic compounds) come together in slow chemical reactions. Flavours and aromas change from primary fruit notes to tertiary savoury ones and tannins clump together to form the sediment you find in aged red wines, simultaneously softening the effect of the tannin on the palate.
When we taste a tannic red wine, we notice a furry, drying, puckering sensation. This is the effect of tannins interacting with the inner surfaces of our cheeks and gums. This has an important role in matching wine with food as tannin compounds bind to proteins in food to form precipitates. Thus goes the conventional wisdom of red meat (high in protein) with red wine (high in tannin).
The presence of tannins on the palate is notoriously difficult to describe qualitatively. There’s no standardised vocabulary for exactly how these chemicals interact with our mouths. As a guide, focus on both the quantity and the quality of tannins. They can be plentiful or few, fine or coarse, smooth or rough; grippy, chewy, astringent, supple or even ‘green’ (an expression for tannins originating from unripe grapes). The effect of tannins reminds some people of particular textures – either real or imagined – such as sand or crushed shells. I personally visualise tiny grains interacting with my inner cheeks. These ‘grains’ vary in quantity, size (how penetrating the tannins are) and shape (how rough or smooth they come across).
Sign up for Jonell Galloway and James Flewellen’s “Celebrate the Chartres Festival of Lights & Autumnal Equinox with a Food & Wine Tasting Masterclass” in France from September 19 to 22, 2013.
About James Flewellen
Dr James Flewellen is a biophysicist at the University of Oxford. James learned his trade in taste through the Oxford Blind Wine Tasting Society, of which he was the President from 2010-2012. During his term, he represented Oxford at many international blind tasting competitions – twice winning the prestigious ‘Top Taster’ Award in the annual Varsity blind tasting match against Cambridge University and captaining winning teams in competitions throughout Europe.
One of James’s goals is to clarify the complex and hard-to-navigate world of wine for both novice and experienced tasters. He applies his scientific training to wine education, illuminating concepts of taste, tannin and terroir in an approachable, entertaining manner. James runs wine education courses in Oxford through the Oxford Wine Academy and is completing the WSET Professional Diploma in Wine and Spirits. He is the regular wine writer for The Rambling Epicure and is the founder of The Oxford Wine Blog. He is also currently co-authoring The Concise Guide to Wine and Blind Tasting – a book surveying the wine regions of the world and how to blind taste.