Tannins are particles that wines pick up from the grape skins. Therefore the only wines with tannins are orange or red wines i.e. those that have spent time in contact with their skins. Tannins are not just found in wine – in fact the most common drinks with tannins are tea and coffee. You will often notice in an overly black tea or over-brewed black coffee a drying sensation. This drying sensation is the tannins at work. Tannins are found in almost all edible plant matter and when extracted into a liquid are what are behind the drying sensation or bitter flavour.
The tannins in wines can be from their grape skins or from oak barrels – though mostly from the grape skins. So, as a general rule we can say that wines with deep colours (those that have spent more time in contact with their skins) will also have high tannins. An exception to this is with grapes that may be lighter in colour but have been spent time with skins that are from un-ripe grapes. These un-ripe grape skins will give un-ripe tannins that are perceived as astringent and bitter.
Grapes from warm-hot climates, which have ripe skins and tannins, will appear soft and silky on the palate. Wines from cooler climates will often not have grape skins, thus tannins, that are as fully ripe - so if they are extracted fully the tannins in the wine will appear bitter and astringent.
NOTE: The tannin level of a wine is directly related to body of a wine. A wine with higher tannins will have a fuller body, and one with low tannins will have a lighter body.
Low tannins – Wines that have low tannins will often have higher acidities that help to balance out the wine instead. These wines can be served slightly chilled if you prefer. The lower level of tannins will help to give the wines a smooth and velvet-like texture.
Medium tannins – Wines that have medium tannins will be perceived as being the most balanced. This is due to being ‘just right’ and having the perfect amount of acidity, sweetness and tannins. Of course there are wines that are exceptions, which will have high acidities and medium tannins, though more often than not wines with medium acidities will have medium tannins.
High tannins – Wines that have high tannins will often have the lowest acidities. Depending on the ripeness of the tannins, the tannins will be either be soft and silky or drying and coarse. Often wines that are incredibly ripe and have a high fruit concentration will also have high tannins. Though the tannins in these wines be soft and add to the texture without leaving as much of an intense drying sensation as you would expect.
NOTE: The amount of tannin present is different to the type of tannin detected on your palate. For example a wine with high tannins could have soft tannins (e.g. Argentinian Malbec or Aussie Shiraz) but could have harsh tannins (e.g. lower quality Cabernet Sauvignon or Nebbiolo). Just like a low tannin Pinot Noir could have either harsh and astringent tannins, or soft chalky tannins.