Wine question: What causes bitter tannins on the finish?

S

SteveTimko

Steve Timko
Uninteresting wine, but it got me to wondering what causes bitter tannins only on the finish. Is it in the vineyard or in the winemaking?
And could it be a flaw that the fruit is some how peeled back, exposing tannins?

2006 Paul Jaboulet An Ctes du Rhne Parallele 45 - France, Rhne, Southern Rhne, Ctes du Rhne (1/6/2009)
Mostly a balanced wine. Standard darker fruit flavors along with a hint of cigar and garrigue that confirms it is a Rhone. The flaws are a sweet midpalate and an unusually bitter tannic finish. Almost lip-puckering bitter. I picked it up for 75 percent off at a Wild Oats store closing, so I'm not disappointed in the purchase, but for the same price at full retail or a few bucks more you can get a much better Cotes du Ventoux, something that Kermit Lynch imports or a good Spanish grenache. Imported by Frederick Wildman & Sons.
 
originally posted by SteveTimko:
Wine question: What causes bitter tannins on the finish?Uninteresting wine, but it got me to wondering what causes bitter tannins only on the finish. Is it in the vineyard or in the winemaking?
And could it be a flaw that the fruit is some how peeled back, exposing tannins?
Click to expand...

Tannins are polyphenolics. The astringency (bitterness) of tannins is related to their size: at very small size, they aren't bitter, but then cross a threshhold where they become intensely bitter, then become less bitter as they increase in size, eventually falling out of solution as sediment. As tannins are exposed to oxygen, they polymerize, growing larger, which is why winemakers put wine in oak barrels, rack or microoxygenate. This is also why we age some red wines, but you already knew that. The tannins also tend to be smaller in unripe grapes, which is why people refer to "green" tannins.

Mark Lipton
 
Mark,
FWIW, I think there is some conjecture about this process, particularly the longer and longer polymer chains ocurring over time. An article I read theorizes that the chains actually grow and then break, regrow and then break, etc. To what extent this theory effects what one tastes is still up in the air but the idea of a simple and gradually larger tannin chain progression may not be the whole story.
Best, Jim
 
But why just show up on the finish? The wine doesn't seem overly tannic until the last few seconds of the the taste.
 
originally posted by SteveTimko:
But why just show up on the finish? The wine doesn't seem overly tannic until the last few seconds of the the taste.
Click to expand...
I find a bit of that to be characteristic of grenache, but I am quite surprised to hear of it in a mass market bottling like this.
 
I've had more than a few winemakers tell me that obvious tannin on the finish tends to be from oak. I admit I have no idea how that might happen, and I don't see how it applies to this wine, but it's what I've heard.
 
It's so strange that this bottle would behave that way. this is usually innocuous wine for pretty popular taste. I wonder if your bottle was damaged.
 
originally posted by Florida Jim:
Mark,
FWIW, I think there is some conjecture about this process, particularly the longer and longer polymer chains ocurring over time. An article I read theorizes that the chains actually grow and then break, regrow and then break, etc. To what extent this theory effects what one tastes is still up in the air but the idea of a simple and gradually larger tannin chain progression may not be the whole story.
Best, Jim
Click to expand...

Jim,
Let's be careful to distinguish microscopic from macroscopic effects. What you're talking about is a microscopic effect, concerning the mechanism by which tannins grow (or shrink). What I was referring to is a macroscopic effect: if you graph the average molecular weight of the tannins vs. time, you will see (I think) a monotonic increase in size over time. It won't be linear growth (barring some freaky coincidence) for reasons of co-operativity, geometric growth, etc. Having said all that, I still question how those chains would break, as the polymerization of tannins generally occurs via the formation of carbon-carbon bonds, not the easiest things to break in the relatively benign environment of wine.

If you have a citation for that article, could you pass it on to me? I'd be interested to read what they have to say.

Mark Lipton
 
originally posted by Thor:
I've had more than a few winemakers tell me that obvious tannin on the finish tends to be from oak. I admit I have no idea how that might happen, and I don't see how it applies to this wine, but it's what I've heard.
Click to expand...

Wood tannin is quite drying, and seems to radically attenuate fruit. Bitter tannin suggests to me too much tannin and alcohol together, or unripe tannin, and/or seed tannin, or some combination/interaction of the above. Not to mention whiskey and Brussels Sprouts.
 
To SteveTimko's original question... If I recall my middle school biology correctly, the highest concentration of bitter-sensing taste buds is at the back of the tongue, nearest the throat. Even when swishing wine around, presumably that's the last area of the mouth to "get hit" with the wine. Perhaps that has some bearing on why bitterness is only sensed at the finish? Hell if I know. But it's a thought.
 
originally posted by MLipton:
If you have a citation for that article, could you pass it on to me? I'd be interested to read what they have to say.

Mark Lipton
Click to expand...

No citation but I recall it being written by Dr. Paul Smith of the Australian Wine Research Institute and cited by Jamie Goode in "The Science of Wine." Apologies for not being more specific.
Also see: http://www.wineanorak.com/tannins.htm
Best, Jim
 
originally posted by Florida Jim:

No citation but I recall it being written by Dr. Paul Smith of the Australian Wine Research Institute and cited by Jamie Goode in "The Science of Wine." Apologies for not being more specific.
Also see: http://www.wineanorak.com/tannins.htm
Click to expand...

Thanks, Jim. As usual, Jamie's article is both cogent and provocative. I found the paragraph most pertinent to this discussion:

Emerging research is suggesting that the traditional account of red wine ageingthat over time tannins get bigger, become insoluble, and fall out of solutionmay be wrong. This has been the traditional paradigm of red wine ageing. You are probably familiar with the explanation: a young red wine may be big and tannic, and after several years in the bottle the tannins will soften, by means of them getting bigger and falling out as a deposit. But this concept isnt based on good scientific data, and what actually takes place in wine ageing is uncertain. This is a huge question, and I doubt generalizations can be made, says Paul Smith. Basically, there are alterations and recombinations of all the components. The classic example is the breaking apart and recombination of tanninsperhaps this mellows them, perhaps they get bigger, perhaps they get smaller. So, while the traditional explanation of tannins getting bigger and falling out of solution may hold, it could well be that tannins are breaking up in the acidic environment of the wine and are getting smaller. Its worth bearing in mind that some red wines age wonderfully with very little or no bottle deposit. Because wine ageing is such an important part of the appreciation of fine wine, it would be nice to know what is actually taking place.

Reading this, I can begin to see why acidity might be important for the aging of wine, an observation that I've long had trouble finding a firm basis for.

He later provides the first understandable explanation I've read for color stabilization in wine. I never understood why anthocyanins, the same pigment found in hydrangeas and other flowers, needed to be "stabilized" or the mechanism by which it occured.

Thanks again,
Mark Lipton
 
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