Cork lets sulfur out?

In his recently published book Uncorked, My Journey Through the Crazy World of Wine (which I am not recommending), author Marco Pasanella writes that cork "keeps oxygen from coming in while letting the sulfur fumes out." Is there something to that, regarding sulfur fumes? I have no idea, although the presence of errors of fact elsewhere in the book provide reason for skepticism.

Sulfur fumes? Aw, c'mon! Many wines are treated with "sulfite" which is a salt of something (likely sodium). It dissolves in water and the sulfite part of the stuff tends to pick up an extra oxygen (or something else) atom and keep the wine from getting other nasty oxidative things happening to it. I have no idea how the sulfite (SO2 component) acts with organic compounds, but that's because I'm not a chemist!
Mark Lipton will probably tell me (and you all) just how wrong I am.
Anyway, "sulfur fumes" in the sense of something in a wine bottle (not a volcano) is total BS!

John

Sulfur fumes? Aw, c'mon! Many wines are treated with "sulfite" which is a salt of something (likely sodium). It dissolves in water and the sulfite part of the stuff tends to pick up an extra oxygen (or something else) atom and keep the wine from getting other nasty oxidative things happening to it. I have no idea how the sulfite (SO2 component) acts with organic compounds, but that's because I'm not a chemist!
Mark Lipton will probably tell me (and you all) just how wrong I am.
Anyway, "sulfur fumes" in the sense of something in a wine bottle (not a volcano) is total BS!

John

Nope, you've got the essentials right, John. SO2 is introduced as potassium (not sodium) metabisulfite. It forms sulfites with the polyphenolics in the wine (and is then called "bound" SO2) but the whole schtick about sulfur fumes sounds like so much marketing BS to me.

Mark Lipton

Wine bottles enclosed with natural cork are generally stored on their sides. Thus creating a cork/wine interface. Over periods of time, wine is absorbed into the cork not necessarily “let out”. The ability of natural cork to “absorb” things is just one of its “natural” characteristics. But then again wine collectors of “older” vintages of wine are concerned with something known as “ullage” (the “empty space” created due to evaporation of wine from a bottle or oak cask for that matter).

Salute

Well, this may have something to do with it if corks breathe. From personal experience, when I fill a wine barrel and have the wine dosed with, say, 30 ppm SO2, after 6 weeks or so, the level in the barrel will drop an inch or so and the SO2 level will have dropped to around 10 ppm, so every time I top up the barrel, I have to add potassium metabisulfite. I'm not sure if the SO2 is passing through the wood or if it is all getting bound.
Tomorrow morning I will be testing my Riesling for SO2 content before bottling, and making adjustments, as necessary. I have never tested SO2 on a wine that has been in the bottle for an extended period of time, but from what I've read, the level decreases over time.

Hi Mark,
I’m not familiar with the publication or its “targeted” audience. Couldn’t the term “sulfur fume” just be another way of describing “free” SO2 (or distinguishing between “free” SO2 and “bound” SO2)? The “free” SO2 will have an odor, the “bound” SO2 could possible be odorless.

Salute

Cork keeps oxygen out? Since when? And sulfur fumes??? This guy could be dangerous.

author Marco Pasanella writes that cork "keeps oxygen from coming in while letting the sulfur fumes out."

The molecular free form of SO2 in wine exists as a gas, so use of the term "fumes" is technically correct. It's true that SO2 is lost through the cork, though the wording "letting it out" is misleading because it suggests that loss of SO2 through the cork is one of the purposes of using a cork closure (and it's not).

Cork most certainly does not prevent oxygen ingress, that statement is factually incorrect.

Nope, you've got the essentials right, John. SO2 is introduced as potassium (not sodium) metabisulfite. It forms sulfites with the polyphenolics in the wine (and is then called "bound" SO2) but the whole schtick about sulfur fumes sounds like so much marketing BS to me.
Mark Lipton

Au contraire, Mark.....it just sounds like absolute and total ignorance by a know-nothing wine writer...and there's a bunch of those out there.
Tom

Nope, you've got the essentials right, John. SO2 is introduced as potassium (not sodium) metabisulfite. It forms sulfites with the polyphenolics in the wine (and is then called "bound" SO2) but the whole schtick about sulfur fumes sounds like so much marketing BS to me.
Mark Lipton

Au contraire, Mark.....it just sounds like absolute and total ignorance by a know-nothing wine writer...and there's a bunch of those out there.
Tom

You're presuming that a marketer wouldn't be absolutely and totally ignorant? That does not jibe with many of my experiences while in marketing. (Although I agree this sounds like the case of both ignorance and bad writing.)

I'd give the writer a pass on such loosey-goosey statements as "cork keeps oxygen out" as his taget audience obviously isn't wine geeks or professionals. I wonder what his target audience is. It obviously isn't ITB types or geeks, and I doubt your typical wine consumer would be interested in his lengthy accounts of the wine trade. He is a retail wine merchant in New York City, and has been for the past seven years, but when he defines Syrah as the principal grape of the "southern" Rhone one wonders how much time he devotes to the business.

Hi Mark,
I’m not familiar with the publication or its “targeted” audience. Couldn’t the term “sulfur fume” just be another way of describing “free” SO2 (or distinguishing between “free” SO2 and “bound” SO2)? The “free” SO2 will have an odor, the “bound” SO2 could possible be odorless.

With the disclaimer that they could be using the term in any way they chose, I can only say that a fume is by definition a suspended solid in air. SO2 can be a gas or it can be dissolved, but it can't be a fume such as smoke. (Likewise, a vapor is a suspension of liquid in air, i.e. an aerosol) If the author was referring to free SO2, he was doing it in a most imprecise way.

Mark Lipton

Isn't the real point that corks supply some oxygen to the wine, and also let some oxygen in, which helps get rid of reductive (sulphurous) smells. Screwcaps let less oxygen in, and thus the wine is more likely to be reductive if the problem is not sorted out before bottling.

Well, this may have something to do with it if corks breathe. From personal experience, when I fill a wine barrel and have the wine dosed with, say, 30 ppm SO2, after 6 weeks or so, the level in the barrel will drop an inch or so and the SO2 level will have dropped to around 10 ppm, so every time I top up the barrel, I have to add potassium metabisulfite. I'm not sure if the SO2 is passing through the wood or if it is all getting bound.
Tomorrow morning I will be testing my Riesling for SO2 content before bottling, and making adjustments, as necessary. I have never tested SO2 on a wine that has been in the bottle for an extended period of time, but from what I've read, the level decreases over time.

Howie,
The barrels do breathe and let oxygen in, albeit at a slow rate. That's one reason that you have the metabisulfite in there in the first place, to scavenge the oxygen and prevent it from harming your wine. I'm sure that you're also right that some of the SO2 is present in "bound" form, too, but a lot of the SO2 has been oxidized to sulfate by oxygen.

Mark Lipton

The barrels do breathe and let oxygen in, albeit at a slow rate.

Has this been proven to be true? I know it is generally believed to be true but I do recall reading once a text on wine making where the author disputed this claiming that all the oxygen pick up came during the topping up process and not through the barrel staves.

The barrels do breathe and let oxygen in, albeit at a slow rate.

Has this been proven to be true? I know it is generally believed to be true but I do recall reading once a text on wine making where the author disputed this claiming that all the oxygen pick up came during the topping up process and not through the barrel staves.

I don't see how one can explain the need to top up barrels (to account for loss due to evaporation) if one doesn't have some limited exchange with the atmosphere through the barrel.

Mark Lipton

I will see if I can find the text tonight. I do recall that part of the logic was that the barrel appears to pull a vacuum based between topping ups. I don't remember on how he accounted for the actual wine loss. It may have been into/through the wood and not between the staves.

The barrels do breathe and let oxygen in, albeit at a slow rate.

Has this been proven to be true? I know it is generally believed to be true but I do recall reading once a text on wine making where the author disputed this claiming that all the oxygen pick up came during the topping up process and not through the barrel staves.

I don't see how one can explain the need to top up barrels (to account for loss due to evaporation) if one doesn't have some limited exchange with the atmosphere through the barrel.

Mark Lipton

Jeez, you think this whole barrel porosity thing might have something to do with the famous "angel's share" I keep hearing about? Shazaam.

In spirits maturation, one of the key reasons for using a wood (specifically oak) barrel is for its rate of porosity---said rate being influence largely by the outside environment. From a cold/damp to a hot/dry environment you'll get from 1% to as high as 10% loss of spirit and water combined---albeit more water because of the size of molecules. The evap serves to both introduce oxygen for greater oxidative aging and to concentrate the spirit and raise the alcohol level.

Hoke, that's it. I found where I referenced it here before. Towards to bottom http://www.wineloverspage.com/forum/village/viewtopic.php?f=3&t=22350&start=0&hilit=topping+vacuum

Worked with a barrel facility for a while. Also worked with distillers learning about oak for aging/maturation.

We learned pretty definitively in both instances that one of the five primary reasons oak is an ideal medium for maturation is the porosity of the oak stave.

In the case of spirits, the diurnal temperature change is what drives the maturation process: when the morning air heats up, the liquid inside the barrel expands into (and through) the barrelwood stave. Very little escapes, but some does, both molecule of spirit and water. As the temperature cools, the liquid concentrates back into the barrel from the wood and very small amounts of new oxygen are introduced. Thus, you get head space, and oxidative aging from the interaction of the headspace with the liquid. The entire process of transpiration and oxidative aging results in less water and more alcohol, so you also get concentration.

The external heat an diurnal difference determines the level of transpiration/oxidation. Even within a small area, it varies. Cognac producers normally split their new spirits into different warehouses, some at low level next to the river for a cool, damp environment, and some in warehouses high up on the hills and exposed to full sun. The difference between the same cognacs in the different barrels is quite literally astounding.

In bourbon country, the same whiskey may be placed in three different barrels, with each barrel being placed at a different level in the warehouse. The maturity (and oxidative aging effect and final liquid level and alcohol contents) will be markedly different from the barrels at each level.

And that's why we're always admonishing whiskey students to not confuse age with maturity when talking about barrel aged products.

All of this is based on oak porosity.

The use of the term "sulfur" is a little akin to that of "mineral". Sulfur fumes would surely be S. Very unlikely. Then you have sulfur dioxide S02, sulfite ion SO2−3, bisulfite ion HSO3−, Potassium metabisulfite K2S2O5, all of which many people call "sulfur". Surely it should not be too hard for writers to understand what they are writing about and use the right term?

On a different, but related, topic, the "sulfur cycle" looks interesting. It does not mention climate change, but acid rain. I am glad that I am not concerned by acid rain, unlike some places on this earth.
http://en.wikipedia.org/wiki/File:Sulfu ... nglish.jpg

Now here's another head scratcher, from the same book. Pasanella claims "champagne should be stored upright [sic] as moist contact with the wine can damage a cork's elasticity, thereby letting in damaging oxygen." Now I'd just snicker and forget about it but he claims that this is confirmed by "both the Oxford Companion to Wine and the Comite Interprofessionel du Vin de Champagne (CIVC)." I checked the OCW and couldn't find anything about standing Champagne upright in the section on Champagne and in the section on cork. Has anybody in the world, other than Pasanella, ever made such an unusual claim? Why in hell should contact with wine damage a Champagne cork's elasticity any more than other wine bottle corks?

Now here's another head scratcher, from the same book. Pasanella claims "champagne should be stored upright [sic] as moist contact with the wine can damage a cork's elasticity, thereby letting in damaging oxygen." Now I'd just snicker and forget about it but he claims that this is confirmed by "both the Oxford Companion to Wine and the Comite Interprofessionel du Vin de Champagne (CIVC)." I checked the OCW and couldn't find anything about standing Champagne upright in the section on Champagne and in the section on cork. Has anybody in the world, other than Pasanella, ever made such an unusual claim? Why in hell should contact with wine damage a Champagne cork's elasticity any more than other wine bottle corks?

Wine is a fairly harsh environment for a cork to be placed in due to its high acidity. Prolonged contact certainly does affect the cork, and most corks that I pull out of older bottles look fairly inelastic to me. The reason that bottles normally lie on their side is that the cork needs the moisture or it will eventually shrink, thereby compromising the seal (and letting in oxygen). Perhaps the compressed state of the "mushroom" corks on Champagne do not dry out the way that corks on still wines do. I dunno. Perhaps what the author is thinking about is all those bottles in the cellars in Reims that are stored upright, in which case it needs to be mentioned that those bottles have crown caps, not corks, on them.

Mark Lipton

I don't see how Champagne can possibly become oxidized through a cork. After disgorging, CO2 bubbles foam up in the neck, displacing any air that may have been in the bottle. Then, the bottle is upright while it is topped off with the dosage and corked, thus trapping the CO2, which is heavier than the air, in the very cold bottle. If anything were to happen through the cork, it would be wine or CO2 leaking out under pressure. It's not a question of chemistry, but physics.