WHAT ARE TANNINS IN WINE?
All wine, including white wines have tannins, though some are described as “more tannic” than others.
Tannins are a group of phenol compounds found in plants, which create a group of chemicals called “Polyphenols“. These polyphenols are, for the most part, soluble in water. Therefore tannins are largely responsible for giving wine a defined structure or body, adding balance, complexity and structure, as well as acting as a preservative to make a wine last longer.
The term ‘tannin’ comes from the ancient practice of using extracts from plants to cure leather (the process still referred to as ‘tanning’). This process exploits one of the key properties of tannins: they have a strong tendency to link up with a range of other chemical entities, most particularly proteins, and when applied to animal hides for example, tannins cross-link the proteins, turning something rather soft and floppy into a material that’s tough and inert enough to make shoes, belts and saddles.
While tannins exist naturally in the grape skins, stems and seeds as well as oak used for wine barrels, the tannins that develop in wine are actually very different. This is because the chemical make-up of the tannins actually changes during the various process during both the winemaking process as well as aging. Tannins are also indirectly responsible for a wine’s aroma even though they don’t have any smell themselves, but in slowly reacting with the wine’s alcohols and esters (acidic alcohols), they gradually erode the initial flowery, fruity aromas found in young wine.
There are two main types of tannins: hydrolyzable tannins and non-hydrolyzable tannins (also called “Proanthocyanidins”). Hydrolyzable tannins (meaning that they are able to be split up and broken down by interacting with water) are commonly found in acidic form in the bark and wood of oaks and other plants, or more specifically, the oak barrels used for ageing wine. Non-hydrolyzable tannins are often found in other plant sources such as tea, pomegranates as well as grape seeds and grape skins.
Tannins also affect the colour of red wine. The bluish-red or violet colour of a young red wine formed by the pigments in the grapes are gradually replaced by deeper, brick-red or dark cherry colours created as long polymer chains linking the grape pigments to the tannins. Higher tannin wines also tend to bottle age better than those that have fewer tannins, and these tannins will actually gradually ‘soften’ over time. So go ahead and save that Cab for a few years! Older vintages are also better if you’re prone to headaches from drinking wine.
Tannins are also one reason why it is recommended that you allow a wine to ‘breathe’ or aerate before drinking it. The air softens the tannins, even in young red wines with “younger tannins”.
White wines have much lower tannin levels because white wines are not typically fermented with their skins or seeds as in red wine production, so the extraction of tannins is minimal. In contrast, the ability to age white wine derives primarily from acidity, but also from alcohol and fruit extracts.
Learn more about the effects of aging on tannins on our Ronda Wine Tour, as well as the differences between French and American oak!