Questions about tannin

One of the wines I like are the petite sirahs from California. The ones that I especially like are mouth-puckering tannic when they are young. To my taste, they have a very bitter finish as young wines that's not very enjoyable. However, after about 10 years of cellaring, that bitterness goes away to be replaced by a long, velvety finish which is very delicious to me. The best ones seem to have a dark crystalline sediment after the cellaring. When I open a bottle and decant it, I always put a finger-full of the crystals in my mouth to chew on them to get a flavor I've never tasted anywhere else.

My questions are: What happens to the wine in cellaring to convert the bitter to the velvet? Is the velvet still considered "tannin" in an altered state? When people extol the health benefits of tannic wines, are they talking only about young wines before the conversion takes place? Where does that interesting tasting sediment come from? Is the sediment a product of the conversion process?

Thanks in advance.

Hi Marc and welcome to the Wine Lovers Page. Here is my understanding of the process. Wines are very complex substances, consisting of water, alcohol, several acids (tartaric, malic, lactic, citric, ascorbic, acetic, succinic, etc.), tannins (which complex and varied, but not entirely stable polymers), aromatic esters, microscopic solids and various other compounds. During bottling, oxygen exposure occurs and in a 2 month or so period after bottling the wine has to recover from this "bottle shock". After that, the various elements in the wine interact with one another over time. Fruit-like characteristics gradually give way to nut-like or earthy (mushroomy?) characteristics. The polymer chains of the tannins combine to form longer chains. These longer chains have a softer mouth-feel. Eventually, as the chains grow longer, they may precipitate out of solution. Often tartaric acid falls out of solution in the form of tartrate crystals, making the wine softer also. These crystals may also act as a seeding mechanism for the long chain tannins to drop out of solution in the sediment. I don't know if all of this is correct, but it is my general understanding.

The polymer chains of the tannins combine to form longer chains. These longer chains have a softer mouth-feel.

That's it, Howie. The two-dollar word for it is "polymerization."

As an aside, I learned about polymerization of tannins from Alberto Benenati, viticulturalist at Catena. But any Mendoza winemaker will do. They're all obsessed with tannins, and they can talk about them at length...

My questions are: What happens to the wine in cellaring to convert the bitter to the velvet? Is the velvet still considered "tannin" in an altered state? When people extol the health benefits of tannic wines, are they talking only about young wines before the conversion takes place? Where does that interesting tasting sediment come from? Is the sediment a product of the conversion process?

Yes, tannins are crosslinked to form larger and larger oligomers as they age. As the size of the tannins increase, their perceived bitterness decreases, often replaced by that velvety feeling. As Howie mentioned, when the tannins get large enough they fall out of the wine as sediment.

Mark Lipton

I don't believe it is quite as simple as Howie, Dave and Mark suggest. Not according to Jamie Goode at least:
http://www.wineanorak.com/tannins.htm

I don't believe it is quite as simple as Howie, Dave and Mark suggest. Not according to Jamie Goode at least:
http://www.wineanorak.com/tannins.htm

Excellent article! Lots of stuff new to me. Although I'm happy to report that I did hear one part of the story from Alberto Benenati correctly. Here's a quote from Goode's article, and Benenati said it in nearly the same way: "While grapes were traditionally harvested on the basis of sugar levels, increasingly they are harvested with a view to achieving physiological or ‘phenolic’ maturity. Indeed, good viticulture can be summed up as encouraging a convergence of phenolic and sugar ripeness, with both at optimal levels at the same time." That's what it's all about in Mendoza, as I understand it.

There is one bit in the article in particular that seems counter-intuitive, and that's the research that says bigger tannins are more astringent:

Second, in general, the larger the size of tannin, the more astringent. ‘For example, when we tested tannins isolated from grape skin, a dp3 (degree of polymerization 3 units) tannin was less astringent than a dp8, which was in turn less astringent than a dp12, and a synthesized dp5 tannin was rated intermediate in astringency between the dp3 and dp12’, reports Francis.

I was always under the impression that bigger tannins had less of an "astringent" effect in the mouth--that this was the point of polymerization. This is one of those moments when I wish I'd studied at least a little organic chemistry...

That's what it's all about in Mendoza, as I understand it.

I guess I have a different understanding. Backing up a little bit: up to the point of phenolic maturity, sugar increases through accumulation, and after that it increases through concentration (i.e., evaporation of water in the grape).

Phenolic maturity is also called the European point because traditional winemakers there, generally speaking, pick when sugars have stopped accumulating but have not yet begun to concentrate.

One of the hallmarks of the international style is that winemakers pick later, allowing supermaturity (i.e., concentration), because that leads to earlier drinking wine with higher alcohol and less astringent tannins, though at the cost of lower acid. To me, that tends to homogenize varietals and dampen terroir.

Mendoza joined that bandwagon (circa 2002 or so) out of, well, respect for Chile's successful export model and in search of higher scores. But there are still many excellent producers there who make wine the traditional way, picking at the point of phenolic maturity (as I understand the term). Why wait for polymerization? Perhaps they are obsessed with tannin because of the drive to make early drinking wines with prematurely velvety tannins.

One of the hallmarks of the international style is that winemakers pick later, allowing supermaturity (i.e., concentration), because that leads to earlier drinking wine with higher alcohol and less astringent tannins, though at the cost of lower acid. To me, that tends to homogenize varietals and dampen terroir.

Love that, Oswaldo. That may be my next wine tasting T shirt - "DON'T DAMPEN MY TERROIR!"

That's what it's all about in Mendoza, as I understand it.

I guess I have a different understanding. Backing up a little bit: up to the point of phenolic maturity, sugar increases through accumulation, and after that it increases through concentration (i.e., evaporation of water in the grape).

Phenolic maturity is also called the European point because traditional winemakers there, generally speaking, pick when sugars have stopped accumulating but have not yet begun to concentrate.

One of the hallmarks of the international style is that winemakers pick later, allowing supermaturity (i.e., concentration), because that leads to earlier drinking wine with higher alcohol and less astringent tannins, though at the cost of lower acid. To me, that tends to homogenize varietals and dampen terroir.

Mendoza joined that bandwagon (circa 2002 or so) out of, well, respect for Chile's successful export model and in search of higher scores. But there are still many excellent producers there who make wine the traditional way, picking at the point of phenolic maturity (as I understand the term). Why wait for polymerization? Perhaps they are obsessed with tannin because of the drive to make early drinking wines with prematurely velvety tannins.

I agree, absolutely. The reason I single out Mendoza--and such areas as the western part of the Colchagua Valley in Chile--is the exceptional dryness of the climate, which results in extra-thick-skinned grapes, which are in turn, of course, vehicles for tannins.

My favorite example of a producer working in the traditional ("non-super-maturity"?) style is Achavel Ferrer, which turns out beautiful Bordeaux-style wines.

There is one bit in the article in particular that seems counter-intuitive, and that's the research that says bigger tannins are more astringent:

Second, in general, the larger the size of tannin, the more astringent. ‘For example, when we tested tannins isolated from grape skin, a dp3 (degree of polymerization 3 units) tannin was less astringent than a dp8, which was in turn less astringent than a dp12, and a synthesized dp5 tannin was rated intermediate in astringency between the dp3 and dp12’, reports Francis.

I was always under the impression that bigger tannins had less of an "astringent" effect in the mouth--that this was the point of polymerization. This is one of those moments when I wish I'd studied at least a little organic chemistry...

Dave if I am right (forgive me if not) you think these inconsistent views are due to your lack of understanding of organic chemistry. I don't think that is the case.

The article is saying that there is no evidence for the "traditional view" of tannins polymerising (yes, getting longer) with time, thus leading to softer tannins. Your impression was based on this traditional view, which is in fact wrong.

In fact, shorter tannins are generally less astringent. And the process of tannin maturation is probably a lot more complex than polymerisation. Some get shorter, some get longer, and there are many other reactions too which may affect the astringency.

Tannins -- Wikipedia:

http://en.wikipedia.org/wiki/Tannin