Heather here from the Paso Robles Wine Club. Ever wonder about tannins in wine? Here I will break down just about everything you need to know about the effects; good and bad on wine.
Tannins are natural polyphenols that can be found in many species of plants, from all parts of the globe. It's believed they are a mechanism of defense against herbivores, having a somewhat wide array of uses in human activity, the main of which, at least historically, is probably the tanning of animal hides into leather – activity from which the word derived. For what concerns wine, they come from the stems, skins, and seeds of the grapes, as well as from the wood of the barrels where the aging process takes place. Furthermore, it is also possible to use wood chips or even add powdered tannins directly to the wine, before, during or after fermentation – a somewhat controversial practice called tanisage.
Most of wine tannin is extracted during maceration and fermentation: the longer the solids – grape stems and/or skins and/or seeds, after pressing – soak in the juice, the more tannins will be extracted. Since this contact is longer in red than in rosé or white vinification, also in order to increase the extraction of color, red wines tend to have much higher tannin content than rosé or white wines. Wood tannins, contributed by chips or barrels, vary greatly, depending on the type of oak used, its age and toast degree, and dissolve into wine through contact.
Different grape varieties have different amounts of tannin: Cabernet Sauvignon and Tempranillo yield more tannic wines than Pinot Noir or Gamay, for example. Like grape sugars, tannins undergo ripening and, as the wine ages, they soften, becoming silky. When young, many wines appear to have short, coarse, bitter and astringent tannins, but, over time, these will combine with anthocyanins, the color pigments from the grape skins, to form longer polymer chains. Eventually, they end up precipitated as sediment. This is why red wine loses its color as it ages and dead wines appear completely flat, without body, weight or texture.
It is widely recognized that a good wine has to show, first of all, balance between acidity, tannins and alcohol: too much alcohol will make the wine hot, muting the fruit and structure, burning the mouth; not enough alcohol will make the wine taste thin and possibly aggressive; too little acid or tannin will cause a wine to taste either overly heavy, flabby, or flat and bland, depending on the quantity of alcohol present... too much or poorly integrated tannin (and acidity) can be either a sign of a badly made wine or a very young one, that may, eventually, become glorious after many years in the bottle.
Thus, despite having no smell or flavor, tannins impart a great deal of complexity to the wine, being one of the main factors responsible for the delineation of its character, while also helping to preserve it. They bind to proteins and precipitate them – the feeling of astringency they leave in the mouth is how we feel the precipitation of the protein rich saliva. Then, a simple way to determine whether a wine is high or low in tannins is to focus in the intensity of its drying sensation. And this is also the reason why a red with big tannins goes well with, let's say, a nice steak: the tannins will not only cut the richness of the meat, but also clean the palate, letting the flavors shine.