When we drink boutique wines we come across stringy, textural proteins called tannins. Many people assume that these proteins are what make a wine dry, this is not correct. Although tannins make your mouth feel dry and astringent, the residual sugar is what makes the wine dry – as in less than 5 grams per litre of sugar.
So what are tannins and why do they feel so “dry” in our mouths? Tannin is a natural polyphenol found in the woody part of plants and the skins of fruit, in this case, grapes. Tannin is also extracted from the barrels that red wine is aged in as the barrels are made from wood too.
To give you an idea of how tannins give a plant structure about 50% of the weight of dry leaves are tannin. Black tea is quite literally almost pure tannins dissolved in water. These are the same proteins that you feel cracking on tongue and “drying” your mouth out when consuming red wine.
Why do we want tannin in wine? Some winemakers try very hard to produce wines that have less or very supple tannins for accessibility, while others extract a lot of tannin. The reason they do this is to add ageing potential, structure and complexity to the wine. Tannins are one of the factors that contribute directly to the ageing potential of wine; they quite literally protect the wine from oxidation.
Wine made with supple tannins, amongst other factors such as lower acidity, alcohol and residual sugar, will usually have less ageing potential and will be intended to be consumed sooner than later. Wine with higher tannin structure, higher acidity and higher alcohol will have a higher ageing potential. These wines are designed for your cellar.
Certain varietals (types of grapes) will naturally offer more tannin extraction in the winemaking process. Cabernet Sauvignon is a varietal that is almost expected to carry higher levels of tannin, a wine usually created to age. Merlot, on the other hand, is a softer, more feminine grape, that offers less tannin usually. White wines have very little or almost no tannin at all. There are, however, many exceptions to the above.
Some folks enjoy tannin and others do not. If you purchase a wine slightly higher in tannin and it does not agree with you, cellar it for a year or two, giving those tannins time to soften and breakdown. You might be pleasantly surprised!