Tannins
A version of this article first appeared in Wine and Spirit in 2007, since merged into Harpers Wine and Spirit.
Without tannins, all red wine would be a bit like Beaujolais nouveau, which makes tannin pretty important for wine structure, grip, texture, colour stability, quality and longevity.
Tannins are colourless until they bind with colour compounds.
Tannins are one of the principal polyphenols in wine and the natural tannins in grapes are all condensed tannins (or proanthocyanidins). These are colourless molecules and they will bind with anthocyanins to form coloured compounds. Jacques Lurton, of the famous Bordeaux wine family, explained “the colour is fixed to a tannin molecule that’s already in the wine [in the presence of oxygen]. [With no oxygen] the ‘free’ colour molecules drop out.” Wine can also contain hydrolysable tannins extracted from oak barrels and chips, or from oenotannins added during winemaking. Oenotannins are extracts of oak, chestnut or grape seeds. They’re regularly used as a fining agent, but they play their part in texture and colour stability too.
Tannins are located in berry skins, pips and to a lesser degree, stems. And some varieties such as cabernet sauvignon, nebbiolo and tannat are renowned for their high tannin content.
Managing tannins is fundamentally important for wine quality.
Managing the extraction of tannin from berries is one of the most important aspects of winemaking and has a significant impact on both the style and quality of red wines. For forward, fruity, supple wine styles, minimal tannin is wanted: carbonic maceration, or a pre-fermentation cold soak to extract colour may be the preferred option.
Tannins, though, need alcohol to be extracted. And as lots of tannin tastes bitter and astringent, covering the tongue, teeth and gums in a gritty coating, managing the maceration of skins and liquid during and after fermentation is key, as it is at this time that phenolics especially tannins, colour and flavour compounds are extracted.
What emerges varies widely according to (a) the temperature of maceration, up to about 35°C, (b) the length of time over which maceration occurs, from a few days to a long month post-fermentation, and (c) the quantity and quality of agitation there is between solids and liquid part, for example the difference between a gentle punching down to a more vigorous roto-fermentation.
Frank Mitolo’s, of Mitolo Wines in Australia, preferred tannin management is to “ferment cool, up to 25°C for purity of fruit flavours; don’t work the fermentation very hard, and use fine-grained oak.”
So the permutations for tannin profile are vast. When it’s right it’s oh so seductively right, and when it’s wrong, boy, are our teeth gritted.
