Chauvet on corks

O

Oswaldo Costa

Oswaldo Costa
Just finished reading the often wonderful Chauvet interview with Kesselring, in which, among many other things, Chauvet argues quite unequivocally for corks by saying that exchange with the atmosphere is absolutely necessary for proper ageing. This goes against the idea that zero exchange is ideal. Last thing I want to do is start another closure debate, but I'd love to hear grounded opinions on zero exchange v. very slow & minimal exchange.

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My understanding is that the alternative closure community is well aware of the need for a degree of oxygen transmission. In fact, screw cap liners are likely to be far more consistent in that regard than a random piece of tree bark.
 
My experience has been that most longtime winegrowers and wine consultants have the same opinion as Chauvet in favor of traditional corks.

. . . . . Pete
 
originally posted by Arjun Mendiratta:
My understanding is that the alternative closure community is well aware of the need for a degree of oxygen transmission. In fact, screw cap liners are likely to be far more consistent in that regard than a random piece of tree bark.
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Well that certainly seems to be true considering the extensive research into and production of alternative [to the original almost hermetic tin liner] positive-oxtrans screwcap liners and DIAM corks with specified oxtrans levels.

However 'well aware of the need for' may be further than certain researchers would be prepared to go where arguments continue over whether ageing requires an aerobic component. In any event wine will usually have some entrained oxygen and, depending on the bottling system and any purging process, the headspace may also contain some.

OTOH 'proper' ageing is another area for argument since the examples of long-aged wine under screwcap are few and don't cover the range of wines/grapes/winemaking where extended ageing is considered necessary/beneficial. And DIAM, despite good reports thus far hasn't been around long enough to have been 'proved' i.e. done the 25+ years - particularly for red wines.

I think there would also be some measure of argument concerning Chauvet's assertion that a cork is porous [it is certainly cellular] when that is characterised as providing 'an exchange of gases through the cork' since I believe it has been shown that, while a cork can provide air from within its cells and there can be some transfer at the glass/cork interface, a sound cork does not 'breathe' through its body.
 
Whenever .sasha opens the '21 Montrose for me, it has not been those with the leaky corks that have held the best wine.

The requirements of wine in the first couple of years may be different than wines held for decades. A cork leaks out a decent dose of air as it is compressed to fit in the neck of the bottle, but this early supply tapers over time. This is not the same trajectory as provided by a predictably leaky artificial cork or other seal.

Corks vary a lot, but the best corks give the best seal and have very, very low oxygen ingress. I never see a trail of red wine up the side of a just-pulled cork and think, "Oh, goody, the wine got plenty of air!" But when I see one where the red is confined to the base of the cork, I'm a happy guy.

But I try to stay out of religious disputes.
 
originally posted by SFJoe:
I never see a trail of red wine up the side of a just-pulled cork and think, "Oh, goody, the wine got plenty of air!" But when I see one where the red is confined to the base of the cork, I'm a happy guy.

But I try to stay out of religious disputes.
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old fizz is the deal sealer for me. when the bottom part of the cork looks like a tree-knot glued to a tightly compressed sponge, all is right with the world.

helps keep the fatsink in its place.

fb.
 
The key thing in Chauvet's assertion seems to be that "micro-exchange" allows the "realization of an equilibrium of oxidation-reduction in the bottle."
 
originally posted by SFJoe:
Whenever .sasha opens the '21 Montrose for me, it has not been those with the leaky corks that have held the best wine.

The requirements of wine in the first couple of years may be different than wines held for decades. A cork leaks out a decent dose of air as it is compressed to fit in the neck of the bottle, but this early supply tapers over time. This is not the same trajectory as provided by a predictably leaky artificial cork or other seal.

Corks vary a lot, but the best corks give the best seal and have very, very low oxygen ingress. I never see a trail of red wine up the side of a just-pulled cork and think, "Oh, goody, the wine got plenty of air!" But when I see one where the red is confined to the base of the cork, I'm a happy guy.

But I try to stay out of religious disputes.
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I suppose some of the greatest bottles of Brdx from the 50s I've had with leaky and loose, yet original corks, is an entirely separate discussion then, is it ?
 
The case for oxygen exchange not being important for aging:

1. Bottles retrieved from the sunken ships, where presumably oxygen exchange through the cork would be extremely limited, have been reported to be in fantastic shape.

2. Certain Chauvet disciples have taken to sealing their bottles with wax, a move that can only be viewed as trying to improve the seal of the cork and to decrease the amount of oxygen exchange with the environment.

3. Corks that can exchange oxygen with the environment can also exchange other gases. Water vapor, for instance, has a higher diffusion coefficient than oxygen or nitrogen, so should pass through a cork faster than those other gases. So which bottles show better aging: those with little ullage or those with more?

The chemistry of bottle aging is way too complex for this simple scientist. UC Davis has identified two different mechanisms for tannin crosslinking, one that they call oxidative and the other which they call non-oxidative. However, when I look at their "non-oxidative" mechanism, it invokes acetaldehyde, something that I associate with oxidation. Perhaps there are internal redox processes that don't require the input of molecular oxygen? I dunno.

Mark Lipton
 
No. 1 is a cool argument! But I thot those Bojo wax seals were just a pesky affectation, and were no better sealants than foil (and that this wasn't even their intent).
 
originally posted by SFJoe:
Stuart, who ought to know, always said the wax was much more permeable than even the worst cork.
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Far be it from me to contradict a fellow chemist, but even if the wax is more permeable, adding an extra layer of wax has got to further retard the entry of oxygen into the bottle, certainly to a far greater extent than a foil capsule would. Whether rats would nibble on the wax seals more than a lead capsule I cannot (thankfully) say.

Mark Lipton
 
No, no, not the rats!

I think Stuart's view is that the space between the wax and the cork would rapidly equilibrate with the ambient atmosphere.
 
originally posted by MLipton:
originally posted by SFJoe:
Stuart, who ought to know, always said the wax was much more permeable than even the worst cork.
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Far be it from me to contradict a fellow chemist, but even if the wax is more permeable, adding an extra layer of wax has got to further retard the entry of oxygen into the bottle, certainly to a far greater extent than a foil capsule would. Whether rats would nibble on the wax seals more than a lead capsule I cannot (thankfully) say.

Mark Lipton
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+1

Plus I think that the 'intention' of the wax seal is to add an extra barrier, however imperfectly, at the top of the glass cork interface to protect against the random possibility of a less than perfect fit of glass and cork in the neck.

And some waxes are much less permeable than others and it would be interesting to know whether Fourrier's or Raveneau's or Cotat's etc etc waxes are actually more permeable than their [presumably even more carefully chosen] corks.

One might reasonably assume that they at least believe the wax has some purpose other than to irritate their customers. Fourrier certainly claims to have conducted extensive tests while also sourcing the 'best' corks from IIRC Corsica.
 
originally posted by Cory Cartwright:
Wax caps sell certain wines better. I had a customer tell me "we could sell more of this if it had a wax top".
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I hope you shot him between the eyes.
 
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