Put A Cork in it”¦or Don’t

I don’t want to give away too many personal details, but for reasons both obvious and obscure, I spent a good part of my weekend making the rounds at wineries. For the record, the obvious reason is “duh, wine.” I don’t mind sharing that one. Anyway, on one tour, the guide noted that corks made from real cork bark may be falling out of favor with wine-makers. I decided to explore the science of why.

For the past four hundred years, natural cork has been the plug of choice for wine-makers the world over. Cork is a particularly well-suited wood: the very best stuff comes from the Mediterranean region, and its structure is such that it can squeeze down into the neck of the bottle and expand or compress to match the shape of neck. This supposedly gives the wine a great seal, allowing it to mature without the threat of oxygen coming in and screwing things up.

But now, wine-experts are not so sure. The corks may not be completely effective in keeping air out. For a wine that gets drunk fairly quickly, that’s not such a big deal. However, for serious wine-drinkers who plan to keep and age their bottles, this air transfer means serious bad news: with too much oxygen, the wine can lose quality.

Unfortunately, that’s not the worst of the problems corks can cause. Have you ever popped open a bottle only to be greeted not with the heady, rich aroma of wine but with the stench of cork? That’s a wine that’s experienced some cork taint, which is just as unpleasant as it sounds. The estimates of the percentage of bottles on store shelves afflicted with taint go anywhere from 0.1% all the way up to 10-15%. That’s not great for wine producers, wine drinkers, or anyone really.

Cork taint comes from a compound called “2,4,6-tricholoroanisole”, or TCA to its friends. Now, these problems only occur under some circumstances, and do not mean that corks should be banned immediately or treated with suspicion. At this moment (OK, if you’re reading at a weird time, maybe not at this moment), cork companies are working to address the issue, but, so are producers of fake cork and cork-alternatives, like screw tops.

Screw tops may be where the industry is headed. They’re cheap to make, easy to use, and for a while, work much better than traditional corks at keeping air out. There is also absolutely no risk of TCA. However, screw tops have an image problem to overcome – many people associate screw tops with cheap wine, not the good stuff, and that can be a huge deterrent to purchase. This is a problem that can only be solved with marketing, so here’s to hoping the ad execs brew something good.

What it all boils down to is that wine makers are going to have to think about and adjust the stoppers that they use for their wine. Instead of treating every wine the same way when it comes to plugging the neck, it’s time to look at the different needs of different wines, acknowledge the limitations of our technology, and adjust the industry accordingly.

And now – pour yourself a glass!

14 replies on “Put A Cork in it”¦or Don’t”

Um, So I talked to my stepdad, who has been making wine for 15 years, and has worked with people who have studied both modern and medieval wine making. He says that the oxygen exchange is necessary to mature the wine. That’s why it’s stopped with cork- it’s water tight but not air tight. Air tightness matters for, say, the fermentation process- that’s why you have an airlock on the carboy- but. . . yeah. . . And it’s to keep out contaminants like unwanted bacteria, particularly “mother of vinegar”– the bacteria whose presence can turn wine into vinegar.

I don’t know who is right now. o_0 Like, the Chemistry in this article is on regardless of the truth, but oxygenation being good or bad is in question.

So I am not an expert like your stepdad, but my understanding was that while some parts of the process need oxygen (yeasts do need some oxygen to ferment), after bottling, the amount of oxygen that’s desirable depends on how long you plan to keep the wine and what you plan to do with it. Like, some level of oxygenation can help some types of wine age and mature, but too much universally spoils wine. It’s all about how much oxygenation is happening – are you planning to store a red for 50 years? Well, your need for oxygen or air-tightness will differ from someone who wants to drink a white wine after a week. And! Some of it will depend on your taste and preferences. So that adds more layers.

Anyway, because of how much corks can vary in how well they keep oxygen out, people are still figuring out exactly how much oxygen, if any, the wine needs once it is bottled to maximize the tastiness. I wish I had an answer or an equation for how much oxygen different wines need, because that’d be awesome. Drunken math!

ETA: It is so cool you brought in an outside expert to weigh in on this issue! Thank you!

I think that maybe the issue is that if it isn’t tight enough, over time the amount of airborne bacteria might reach a critical mass of sorts.

Mother of vinegar is an airborne bacteria. This bacteria ferments Ethanol producing Vinegar. If you get a bottle of unpastuerized vinegar, sometimes a film will develop on the top. This is a colony of Mother of Vinegar, and can be added to wine or cider to make more vinegar. It is harmless, and if it looks too off putting, you can strain it out with a coffee filter. The vinegar will still be good.

My theorizing is that if it isn’t tight enough, the gradual build up of this sort of bacteria can cause a wine to turn. But I’m not a micro-biologist, so I’m not even sure if this is possible or if it is within the lifespan of the organism.

What you’re saying is interesting and I haven’t read any studies about airborne bacteria and wine. A cursory search of the literature suggests that bacteria (and mold and yeast) can pose a very real problem to wine and wine makers.

In this case, though, I am speaking about the effects of oxidation, which only requires the presence of oxygen and a catalyst. So to give a more common example, rust is the result of iron oxidizing. Since many compounds in the wine can oxidize, oxidation affects the flavors, aroma, color, etc, of the wine in a decidedly negative way. I’m not saying that all oxygen is going to hurt the wine, just that too much over time will. There is a delicate balance between enough oxygen and too much.

ETA: I just wanted to be clear that the problem of bacteria is definitely real, and the process of wine turning to vinegar does use bacteria,  just as you described (though I am not sure about the airborne part). Oxygen is a necessary component for this and other issues.  I just wanted to emphasize that the presence of oxygen was necessary not just for this very real issue, but for other problems, too.

I hope this makes it more clear. I feel like I am just muddling things up more. Oh no!

Great article!  It’s funny that people will choose a bottle based on cork vs. screw top but they will.  Having put together wine lists for restaurants before, ordering bottles with a screw top can be dicey.  People get a offended by a $40 bottle with a screw top.   It’s a bit of a catch-22 for the wineries.  Synthetic corks and screw tops are better for them in  various ways, but the marketing can screw them over.  I’m all for the cork is better myth dying.

In other fun wine facts, bottles with a punt (indentation) at the bottom are generally of better quality, though I have nothing to back me up on this other than someone told me and it seems to work well when I’m picking a new bottle.

Very interesting! I tend to buy a lot of screw-top wines anyways, because I hate using corkscrews and screw-tops are pretty common with whites (I can’t drink reds, sadly, due to migraines). Maybe it’s different in CA, but it doesn’t seem to me that it’s that strongly associated with a lower-quality wine.

I had read about New Zealand making a big change in how they bottled/stopped wines, so I am glad to see corroboration from a real life New Zealander! It’s interesting how Spain actually requires wine to be corked with real cork to get classified as D. O. (apparently an important classification for quality wine) – and, unsurprisingly, it is a big natural cork producing region. I’m actually kind of excited to see how the cork-wars play out.

Intriguing! I’ve noticed that many wines are headed towards the faux cork stuff, but I had no idea why. What an excellent conversation starter!

I wonder about screw-top wines. Normally I stay away from them, having had bad experiences with them in the past. Howver, my favorite Riesling (Relax) is a screw-top and I adore it. I’m thinking the best bets here for companies looking to dispel a screw reputation *wink* will be word of mouth.

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