Musing on Tannin

Last night, I found myself thinking about tannins. You'll notice I'm not just saying tannic acid, because tannins are complex polyphenol compounds, and are more than just a simple acid. And you don't get them in your wine just from the incusion of skin, stems and seeds. Oak imparts subtle amounts of tannins as well.
So what was eating me? I was wondering just how tannins soften. We've all said it..."tight tannins" "soft tannins" "gripping tannins"...I could go on. What really happens to tannins when wine ages?

So I started with the Wine Bible, by Karen MacNeil - always the first book I reach for. Among her insights I found enlightening was that part of the genius of a vintner is picking grapes not just when the sugar levels are correct, but when the tannins are fully developed as well. Picking too early, even when the sugar level is nice, may have immature tannin phenol compounds that come back in the wine with green, gripping tartness. How do you tell when the tannins are ripe? Only by tasting the grapes.

So what happens to the tannins when wine ages? The best explaination I found was from this excellent wine site, Wineanorak.com. There are two trains of thought here; one that the tannins get bigger by bonding to different compounds in the wine, which give the perception of softness, and then dropping out as sediment. The more current thinking is that in addition to binding onto other compounds and acids in the wine, tannins are also breaking some of these down into smaller particles. This would explain that many aged wines that show as soft have little sediment.

If you're interested in the chemistry of it all, click the link to the tannin paper above. (btw, Anorak is slang in the UK for dork!)