MSNBC Article on Cork

Could be true, but hopefully they will be relegated to "retro" status by then. Or sooner. _Much_ sooner!

I'm lobbying as hard as I can at the winery I'm working out of. The head winemaker's amenable to the idea of screwcaps, but the cost of changing over the bottling line is substantial, and there are significant technical issues that need to be resolved. The main ones concern inert gas sparging of the bottle and cap prior to closure. Apparently, the wineries that are now bottling under screw caps address this issue by slightly over-sulfiting the wine prior to bottling to compensate for the air trapped in the bottle in the process. He doesn't like that approach, and I can't mount a strong defense to that objection.

Tom S

Tom, you simply don't *need* inert gas with screw-caps. That's quite a common misconception/prejudice. Also, you need *fewer* SO2, in no way more.

Please mail me via the reply button (will give you my real mail address), I guess I might have some very interesting information for you.

M.

I don't understand how bottling under screwcap would obviate the need for sparging of the air from the ullage of the bottle. I _do_ understand that setting the minimum correct level of free SO2 for the pH of the wine would be sufficient, since a screwcapped bottle is truly hermetic, so the free SO2 will stay where it was when the wine was bottled.

Tom S

Hi, Michael -

"Reply" didn't work. My message was returned as undeliverable to you. :^(

Tom S

OK then, try "pronay [at] chello [dot] at" or "pronay [at] pronay [dot] com".

M.

Very simple: Getting the air out of the headspace is a technique you need when using bark or synhetic stoppers, in order not to create overpressure in the bottle that might result in leakage and/or pushing out the cork. No need for that under screw-cap.

M.

I share Tom's reservations about the use of screwtops obviating the need for the use of an inert gas or a vacuum when bottling a wine. I say this as an advocate of screwtops. Let's try to keep this conversation in the group because I think it is an important one for members of this group.

Vino

OK, care to elaborate on your reasoning? For my part, it would seem that the small amount of gas in the headspace of the bottle is small potatoes and should be easily negated by a small amount of sulfite. Since the screwcap-sealed bottle can exist for quite a while (if not indefinitely) at higher-than-ambient pressure, the usual justifications for sparging/evacuation don't seem particularly germane.

Mark Lipton

You're the chemist, Mark. Calculate the increase in ppm free SO2 to titrate

AFAIK, what you've suggested is what they are doing in New Zealand, Bonny Doon and other places that use the Stelvin caps. I can't think of a strong objection to it offhand, but I'd still like to see inert gas sparging employed instead.

Tom S

So, next we will have to say, my wine has gas...

higher-than-ambient

Now you've made me think harder about my position. But isn't that what forums like this are all about?

First, I'd like to clear up a couple of things. I'm not familiar with the term "sparging" (or "sparge", I assume). My dictionary defines it as "to splash or sprinkle". I'm not clear how this applies to the bottling of a wine. Are you using it in the same sense as "purging" or "pulling a vacuum"? Another thing I've never thought about before is whether a bottle intended for a screwtop is slightly smaller in volume than one intended for a cork. This would seem to be required in order to retain the same amount of ullage, since a cork takes up a not inconsiderable volume in a bottle.

Are you saying that one of the disadvantages of a bottle sealed with a cork is that high internal pressures can push out the cork? I've seen this happen with bottles that have been subjected to higher than normal heat, but my problem with such bottles is that the wine may have been damaged. The fact that the cork is pushed out a little is a minor consideration. With a screwtop, the wine may have been overheated and there would be no external evidence that such a thing had happened.

Basically, I just don't see why the same considerations regarding the use of an inert gas in bottling would be any different for a screwtop than a wine bottled with a natural cork. The use of sulfite seems to be an irrelevant issue here, but I could be convinced otherwise.

Vino

screwcap-sealed

higher-than-ambient

Nope. There are vacuum corkers and there are bottle spargers. They perform different functions.

Vacuum corkers do pretty much that: they pull a partial vacuum on the neck of the nearly full bottle (very quickly) and drive the cork into the evacuated space. The idea is to eliminate the effect of forcing the cork into the neck of the bottle and compressing the gas in the neck into the wine.

Spargers shoot a blast of inert gas into the bottle just before it is filled, so that the splashing that occurs during filling does not result in oxygen pickup in the wine. In the case of screwcapped bottles, it would probably be best to sparge the empty bottle, fill it with wine, and sparge the neck (ullage) of the bottle _and_ the inside of the cap _an instant_ before capping the bottle.

Another thing I've never thought about before is

Yes, I believe they are.

Read the above. The processes are _similar_, but there are some significant differences. For one thing, vacuum corking is no longer necessary with screwcaps, but a second sparging, just before capping, would be best.

Tom S

Salut/Hi Tom S,

Just jumping in pedantically le/on Tue, 23 Sep 2003 04:54:16 GMT, tu disais/you said:-

That's correct, as in "Thou shalt sparge me with hyssop and I shall be clean".

the same sense as "purging"

Yes, he is. It's an incorrect use of an old word. However we mustn't blame Tom for this as it appears to be a currently common error. Because, thinking about it, blasting an inert gas into a bottle can be perfectly correctly described by the word "purge". When I was a chemist, one of the things we used to do before taking boiler water and feed pump water samples, was to "purge" the lines.

I accept that this is a current misuse of the word, Tom, as I've said above. "Purge" would be correct.

One thing to keep in mind is that the screwcaps are close to a perfect seal. In the AWRI closure trial comparing screwcaps to a variety of stoppers natural and synthetic, only the wine under screwcap developed "rubberlike aromas". Why? It had nothing to do with the plastic lining of the screwcap but rather came from reductive changes in the wine - presumably a slight H2S problem that became a mercaptan issue. They had, in fact, done a second sparging (with nitrogen, I think), as you suggest. As you would expect, the wines under screwcap won the contest for retaining SO2 but they were also the only ones with the mercaptain problems. The lessons I take from this: (1) you'd better not have even a trace of H2S in a wine to be bottled under screwcap and (2) a little oxygen under that screwcap at bottling might not be such a bad idea.

- Mark W.

Picky, picky Ian! :^D Nobody would know what I'm talking about here if I called it "purging". That's a word that simply isn't too food-industry friendly - if you get my drift. {8^p~~~|

Tom S

Why do you say that last? The presence of oxygen would in no way forestall an incipient H2S or mercaptan problem in a screwcapped bottle. Only prior cellar treatment can avoid that. Wines bottled cork finished can have H2S and mercaptan problems too.

Tom S

Because a little oxygen (which can get around the outside of an imperfectly cork seal) will oxidise the H2S, thus removing it. A well sealed cork will retain H2S, as you pointed out. The problem is that there are a lot of badly sealed cork!

At our winery, having gone to screwcaps where possible, now check the wine with a little dose of copper prior to bottling. If we can't pick the coppered wine as being less preferred, then we add it as a matter of course.

My view of screwcaps is that, as with any new technology, you can't just go in and do everything that you used to do. You have to assess how things have changed, and how you will react to that change. And this is what many people have not done, and why we are seeing teething problems with screwcaps. Give it a few years, and people will figure out what they need to do to counter the "bad" things.

Cheers,

Andrew P.S. Does anyone have any good ideas for non-cork seals for sparkling wine? And I mean ideas that won't put off customers - we've considered crown seals, but they might be a little off-putting to the ponces trying to distance themselves from beer. And, having disgorged a few thousand bottles, I know that crown seals can become lethal missiles more readily than corks!