Tannins – that’s a complicated story. In wine tasting, as well as in their chemical way. Just look at that...
They are found primarily in red wine, rarely present in rosé wine, and are practically absent in white wine. They mainly derive from the grape, where they are stored in skins, pips and stems, but can also originate from the oak wood barrels wherein some wines mature. They belong to the family of polyphenols (natural antioxidants that are good to our heart and circulatory system) and they often have extremely diverse and complex structures. The name “tannin” is more of a folkish nickname. Their real names are Catechin, Ellagitanin or Proanthocyanidol. And it may even be worse ... The nickname comes from the process of “tanning” which transforms cow skins into leather jackets. Tannins cherish a particularly close relationship with proteins, forming new chemical compounds and denaturalizing them. This prevents the cow skins to foul.
In wine this affinity is used in the traditional “fining” of red wines with egg white, while the same reaction may cause a slightly rough and dry feel on tongue, lips and palate during tasting of red wine, because the tannins get hold of the proteins in our saliva. This can even checked when looking into the sink after having spit red wine. The small, dark red streaks you’ll recognize are genuine tannin-protein complexes.
So what are they good for?
Tannins in wine are good for taste! The amount of tannins you may find in a grape primarily depends on the grape variety. While grapes of Cabrenet Sauvignon, Malbec and Syrah are rich in tannin, Grenache and Merlot are rather moderate and Cinsault and Pinot Noir even show small amounts of natural tannin. The taste of tannins is closely related to ripening. The riper the grapes, the finer and better they taste, giving structure and body to the wine. Lack of maturity leads to hard, bitter and aggressive tannins.
“I asked Pascal (Verhaeghe) for the key to the phenolic ripeness and silky tannins. He says it’s down to the pips, or seeds; they must be 100% dark brown and if you bite into one it must even be a bit sweet, that’s the key.”(Excerpt from an article on Wine & Design).
In return, the actual tannin amount that’s finally found in the bottle and the glass, is related to the work done by the winemakers in the cellar. They decide in the end how much tannins they want to extract from the grapes to make their wines to taste pleasant and balanced. However, the more tannins you have in a wine, the longer it should age - in barrels, in tanks or in bottles, to literally “polish” the tannins and make them taste smooth. Tannins also appear to contribute to aging capacity of wines, though the calculation “more tannin = more aging potential” doesn’t always add up. In addition, there are many fine, lighter reds and even whites without tannin, which can be stored for years.
Well, wine is just not mathematics ... And even if we track down its molecules, wine still keeps a lot of secrets from us.