Variations in Humidity

Consumers ... blah blah we are told by the industries are the cause of many of our maladies. I find that as consumers we are not given the choices. In some period it must have been more economical to use corks. I like those white plastic corks.

Joe

"Mark Lipton" in message news: snipped-for-privacy@purdue.edu...

I should mention that those notes are nearly two years old and might have appeared here in a more timely fashion, along with other information, except for the extraordinary sequence of events, which I've only partly articulated here (and still imperfectly assimilated) that knocked this newsgroup successfully and persistently off my radar for some years (and possibly also the radar of other earlier contributors as well).

Only recently when I looked at rec.food.drink I saw the too-familiar minor non-wine traffic and dropped a note to "Antoinette," who loves food (1-Feb-04) and I included even a reference or two to Austria. And this was BEFORE I knew about A.F.W. and that I would run into M. Pronay here. (I met Mr. Pronay briefly in 1996; that was three years after I had found myself unexpectedly, and also briefly, on TV in his country as a California visitor during the recovery from the preposterous "glycols" scandal of the middle

1980s that should be taught and immortalized as a cautionary tale about popular journalism on technical topics, just as, closer to home for me, and in a different part of the wine industry, the AxR-1 debacle is becoming immortalized. By the way, Paul Draper had campaigned against AxR-1 years ago while at Ridge; some of his comments were printed in the newsletter there after the scandal broke, and I asked if they could be posted on Ridge's Web site, I don't know however if they have been.)

You are probably right, but formation of sediments most probably happens with the oxigen dissolved in wine without any need of further input through the cork.

M.

But, if that were true, we'd expect all the sediment to form almost immediately upon bottling. The sulfites in wine guarantee that there will be no dissolved oxygen in the wine for long. In fact, it seems to me that the oxidation of the phenolics can only take place after the consumption of the sulfites (well, perhaps only after the sulfites are fully "bound" in the wine), which to me implies that some amount of oxygen must be introduced into the bottle during the course of bottle aging.

Thanks for your sources. I do admit feeling queasy about going mano a mano with such luminaries as Peynaud, but as a chemist I don't see any way of reconciling my views with his on this matter. One thing that I've long wondered about is whether the source of those statements is the measurement of dissolved oxygen in the wine; if so, it's entirely possible that the levels of dissolved oxygen were below the threshold of their measurements because of the rapid consumption of oxygen in the oxidation of the tannins. Just an idle thought, I admit...

Mark Lipton

Your chemical sense would expect that - not me ;-)

To be honest, I don't understand enough in chemistry to follow you. What I do understand are opinions like "At best, cork *is* as gas-tight as a screw- or a crown cap" - and Deposit would imho form in screw-capped reds exactly the same way.

We have the example of air-tight crown-caps in the champagne industry where some wines regularly age 10 and more years under crown-cap (Krug Vintage), and reference bottles in the wineries after 20 and 30 years show no irregularity in ageing.

If there is any difference, may I cite Peter Gago from Penfolds who is experimenting with upscale reds under screw-caps 9 and 10 years (there's even Grange under screw-cap for test purposes): "Ageing process under screwrcaps happens in a slightly slower pace as under cork. It's like having wine from a cool cellar compared to a normal one".

M.

All of that assumes that the presence of oxygen is necessary for polymerization of phenolics, which may not be the case. Redox reactions may occur without the presence of any oxygen at all; Oxidation or reduction are all a matter of gain or loss of electrons (depending on which direction you look at it).

There are a couple of other factors (besides the cork) that may well influence the rate of reactions within the aging process. (1) The high proportion of water in wine tends to disfavor organic reactions. (2) What about the possibility that the glass surface, with its trace impurities, acts as either a catalyst or at least a necessary substrate for the polymerization of phenolics? That would tend to explain the more rapid aging of wine in small format bottles (more surface area of glass per unit volume).

Tom S

True, but can you suggest another oxidant powerful enough to oxidize a phenol that is likely to be present in wine? I can't.

Not really true, Tom. Enzymes routinely catalyze organic reactions in what is essentially water. True, some organic reactions are incompatible with water, but polymerization of phenols ain't one of them...

But catalysis doesn't get us off the hook, because you still need an oxidizing agent. Water and glass are incapable of acting as oxidants in this case, so we are left with very few players. Let's also keep in mind that wine at the time of bottling is in a reductive state, so oxidants will be few and far between.

Mark Lipton

There simply is no scientific evidence nor data, neither in the one nor in the other direction.

What we do have, however, is what rightly is called "anecdotical evidence": Champagne that has matured perfectly under crown caps, and reds (and whites) from down under that aged extremely gracefully.

Australia's Tyson Stelzer perfectly summed up the discussion in his recent book "Screwed for Good. The Case for Red Wine Under Screw Caps." A central chapter ("Buried Treasures? Old Reds Under Screw Cap") can be found here:

M.

Mark, what do you mean when you say that "wine at the time of bottling is in a reductive state". Although the science of bottle ageing is poorly understood, from what I've read, possible sources of oxygen in the wine include small amounts dissolved in the wine during racking (including, for example, consolidating wine from barrels into one tank for bottling), during the bottling process (although even home winemakers are taught to minimize this), from within the cork itself as wine saturates it over time and the (variable) permeability of cork. Protecting wine from oxidation caused by oxygen dissolved in the wine during bottling is one of the main reasons (along with it being their last chance) winemakers typically bump up SO2 levels before bottling.

As I said in my other post, I certainly accept that the primary bottle ageing mechanism is reductive. But like you (I think), I think it's far from proven that the cork plays no role at all. I think some of those who are upset enough about tainted wine to immediately put everything under screwcap are perhaps just a little to eager to dismiss the effects of cork permeability. Maybe none of corks contributions are positive, I don't know - I just haven't been convinced. And I would be happy to *be* convinced - if screwcaps are indeed the all-purpose answer, then life would be simpler!

- Mark W.

that the aging of wine involves both aerobic and anaerobic processes, implying that some amount of oxygen is essential for proper aging.

Mark,

Not being a chemist, I admit to being quite confused by this whole discussion. Are you saying there is very little oxygen in the small air space in the neck of the bottle, after bottling? Or are you saying that the sulfur quickly binds with this oxygen, or any dissolved with the liquid (so that any aerobic reactions must be accounted for by leaking corks)?

Thanks for translating this for the lay reader.

Tom Schellberg

Tom, You've got the gist of it. The sulfites added at bottling time will rapidly consume any oxygen trapped within the bottle, so any oxidative processes taking place in the year(s) subsequent to bottling strongly argue for the influx of new oxygen -- through or around the cork, as the case may be.

Mark Lipton

p.s. Feel free to expound at legth about the economics of wine in revenge for this thread! ;-)

It is this last statement that I was referring to. The added SO2 means that all the oxygen present at the time of bottling will be consumed soon afterward. From that moment on, the wine is in what I called a reductive state -- the tannins in the wine can serve as reducing agents -- unless oxygen finds its way into the sealed bottle.

There are so many factors at play here, Mark, that it makes my head hurt. Is the cork a hermetic seal? (I doubt it) What are the processes that account for bottle aging? (complex issue) Is a screwcap a hermetic seal? (probably moreso than a cork, but unlikely to be perfect, either) etc., etc.

Some of my view on this matter comes from my experience in lab: I've observed oxygen diffusion through 5 mm of plasticized polyethylene against a pressure gradient. It's been noted that sealed glass ampules show the (very) gradual diffusion of oxygen into them over the span of years. In any contest involving the diffusion of oxygen, my money is on the oxygen. It floats like a butterfly and stings like a hornet! ;-)

Mark Lipton

So what would be the theory of wine ageing under crown or screw cap? (Don't tell me it doesn't age - in fact wine ages even more gracefully than under cork.)

M.

If that is true - and I have not the slightest reason to doubt -, then abolish this peace of bark in the neck as fast as possible, please!

M.

To answer your (presumably rhetorical) question: it's a reductive process, isn't it?

But here's another (non-rhetorical) question.... what is the mechanism for the reduction of the volume of wine (increased ullage) over the years?

Yes, thank you.

Seepage. But I guess you knew that ... ;-)

M.