Throughout my book and indeed any discussion of wine, there are many references to tannins. Tannins are chemical compounds known as phenols which are found throughout nature in most growing plants, in fact 50% of the dry weight of leaves consist entirely of tannins. Tannin is actually tasteless, it is a texture; you feel the coarse particles which stick to the surface of your tongue and teeth. The best way to think of tannins is to imagine sucking on a used teabag. The puckering and astringent sensation in your mouth is the tang of tannin. One theory for the prevalence of tannins is that it is Nature’s way to discourage animals from eating the leaves and stalks before the fruit and seeds are ready for dissemination. Some grape varietals, especially white grapes, have little or no tannins while other grape varietals – most notably Cabernet Sauvignon – have very high levels of tannins in the skin.
The word tannin comes from the German word for oak tree ‘tannenbaum’ from which we derive the words tan and tanning. (Oak tannins have always been used for turning animal hides into leather.) As we will see later, the tannins in oak play an important part in the aging of wine in oak barrels. A red wine with very low tannins such as Beaujolais can be drunk extremely young. A Bordeaux wine with very high tannins cannot be drunk when young; it would be impossibly astringent. Wines high in tannins need to be aged, preferably in oak, until, with the passing of the years, the harsh taste of tannins has mellowed. Moreover, with age, the Bordeaux wine has not only lost its astringency and become drinkable, it has substantially improved and those initially harsh tannins have added complexity and maturity to the taste. Without tannins, Beaujolais will not age and will deteriorate rather than improve while, thanks to tannins, Bordeaux wines just get better and better.
Although it’s true that thick-skinned grapes such as Cabernet Sauvignon have more tannins than thin skinned grapes such as Pinot Noir, there are too many other variables to make a definitive list of grape varietals by tannin level. Where and how the actual grapes are harvested, how long the skins are macerated during fermentation and how the winemaker treats the must and how he blends the juices makes it impossible to say that a Sangiovese will always be less tannic than a Syrah or more tannic than a Zinfandel. A selection of grape varietals is listed in Chapter Eight from light to heavy or full bodied, but it is a general list and includes more factors than just tannins.
In her splendid Wine Bible, Karen McNeil, has listed red varietals by tannic level, from least to most tannic: Gamay / Pinot Noir / Sangiovese / Grenache / Zinfandel / Syrah (Shiraz) / Malbec / Merlot / Mourvédre / Cabernet Franc / Cabernet Sauvignon / Petite Sirah / Nebbiolo.