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Tannins - What exactly are they?

“Wow, a lot of tannins in this wine”.  How often have you heard those words without a complete understanding of what tannins are?  Well in this brief article we'll cover tannin's composition, how to recognize them, and their role in making and preserving wine.

 A quick chemistry lesson

Tannin is an old term whose roots are from “tanning”, the practice of curing leather, making animal skins into shoes, belts and expensive handbags.  For the chemists out there, tannins are a group of polyphenolic compounds that exhibit the common characteristic of being highly reactive.  Tannins facilitate the gathering of and combining with other molecules that surround them.

Tannins in wine come from grape skins, stems and seeds.  Mother Nature is very clever in her use of tannins in grapes.  If you've ever been in a vineyard early in the growing season, try picking and eating one of those very small green grapes.  The combination of acids and tannins make them inedible, not only to us humans, but more importantly birds and other plant eating creatures that visit the vineyard.

Recognizing Tannins

How do you know that a wine contains a lot of tannins?  The presence of tannins in relatively small quantities (100 - 1500 mg/L or about one tenth of one percent) is easily detected in wine tasting.  The difference between these relatively small amounts is significant.  Tannins can be tasted - they are bitter, one of the five primary taste sensations.  They are, however, much more likely to make their presence known due to their astringency.  Astringency is a feel rather than a taste, and is best characterized by a sense of “cotton mouth”, a puckering and friction on the walls of the mouth.  When you quaff a large helping of a big young Cabernet Sauvignon, it's the feeling that your mouth wants to collapse inwardly and is in desperate need of rehydration.

Tannins in wine making

Tannins are present in both red and white grapes, however, since the separation of skins from the juice in white wine occurs before fermentation,  white wine has little time to absorb tannins.  From a style or structure point of view, tannins are the major component of red wines; acidity the major element of white wine.  Tannins can also be introduced from aging in oak barrels; however this influence is very limited.

Tannins are very strong anti-oxidants, and thus serve a key role and preventing oxidation and allowing red wine to age for years.  It is generally understood that with aging, tannins “soften” although the precise reason for this is not clearly understood.  There are competing theories as to whether tannins combine and precipitate or settle out of the wine, or whether they may actually break up into smaller compounds, exhibiting less influence on taste and mouth feel.  Regardless of which process occurs, a well-aged red wine will have only the softest of tannins and be delightfully drinkable!


Fast Facts:

Tannins are polyphenolic compounds
Present in red wine
Help suppress oxidation, allowing red wine to age
Produce a puckering feeling in your mouth

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