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The Reduction Myth

Screw-capped bottles are no more vulnerable to chemical taint than those under cork
Photo by: David Yellen

Posted: Jun 23, 2011 1:59pm ET

As twist-off wine closures become more and more prevalent to prevent the foul effects of cork taint, a critical minority claims to find more wines under screw caps affected by sulfides. A new study from Oregon State University disproves that notion. Researchers tested the same wines under corks and various types of alternative closures in real-world conditions, and found no difference at all.

The study, due later this year, debunks the idea, promoted by screw-cap skeptics, that sulfur dioxide and naturally occurring hydrogen sulfide in wine can get worse or develop into other, nastier-smelling taints, such as dimethyl sulfide, in the low-oxygen conditions of a bottle sealed under a spiral closure. In other words, if you sense these taints in a bottle of wine, blame the winemaker, not the closure.

In high concentrations, sulfur dioxide smells like burnt matches and hydrogen sulfide like rotten eggs. Dimethyl sulfide smells like rotten cabbage. Some cork promoters insist that naturally occurring sulfur compounds in wine need oxygen in the bottle so they do not form those nasty compounds. Corks, they maintain, can let just enough oxygen in to do the job.

Not so fast, said Argyle winemaker Rollin Soles. "How often have we tried 20- or 30-year-old wines sealed under perfect corks that kept great fruit freshness? Take them to the lab and you find very little dissolved oxygen, which is exactly what you find under screw cap."

Soles sent me a copy of a poster previewing elements of the study, which was distributed at the American Society of Enology and Viticulture this week in Monterey, Calif. Indeed, after three years in the bottle, the closure had no measurable effect on hydrogen sulfide or dimethyl sulfide concentration. The DMS graph on the poster looks like a tree farm, all the bars at the same height. The other graphs, for other vile compounds, look similar.

Although the wines had minimal amounts of both sulfur dioxide and hydrogen sulfide going into the bottle, the amounts decreased over three years in all closures, and the screw-capped wines developed none of the odious chemicals. Zero.

The scientists tested bottles over three years of 2008 Argyle Pinot Noir and Chardonnay bottled under a variety of closures—three screw caps with different liners, natural cork stoppers in bottles positioned upright and top-down, and a synthetic cork. A hermetically sealed ampule served as a control. The wines were tested in laboratories at Oregon State University in Corvallis and at Gallo Winery in Modesto, Calif.

"There's always a little bit of [hydrogen sulfide] in wine," Soles explained. "As winemakers we have to to control it in the winery. But even if you go into the bottle with it, it's not going to go to those really stinky guys you can't do anything about."

It's the yeasts, said Soles, that develop those chemicals, and it happens during and after fermentation, not in the bottle. (Unless, by some winery error, some of those live yeasts survive into the bottle.) "It's a microbial pathway, not a chemical pathway," he said.

How does such a misguided notion get started? My theory is that a few critics, skeptical of screw-capped closures, found these noxious characteristics in a few screw-capped wines. With no cork-finished bottles of the same wines to compare them with, they blamed the closure. Of course, we find these characters in cork-finished wines all the time, but no one blames the cork.

It's kind of like superstitions that baseball players indulge in. If they put on their socks before their pants one day and go 0-for-5 and make an error in the field, you can bet they're putting their pants on first for the next game. Finding rotten cabbage smells in your first samplings of screw-capped wine is a vinous equivalent of putting your socks on first.

The moral of the story is, don't be superstitious about your wines. I drink screw-capped wines all the time. I actually prefer them. And I age them with confidence, knowing that a bad cork isn't going to ruin a percentage of them. As for stinky taints, I find much less of them in twist-off bottles than I do in corks, but I don't credit the closure for that. Maybe it's that winemakers who use screw caps pay close attention to the chemistry of their wines. For me, that's all to the good.

Andrew J Walter
Sacramento, CA —  June 23, 2011 5:59pm ET
amen....Keep fighting the good fight. Maybe the day will come that the infernal 17th century invention will be retired for good
James Peterson
San Antonio, Texas —  June 23, 2011 8:28pm ET
I just saw a print ad last week calling on wine lovers to save the earth by using real cork and not buying wines with screw tops. There is your next sham objection. Yes, keep fighting the good fight. I'm with you!
Adam Wallstein
Spokane —  June 24, 2011 12:23am ET
Down with cork!
David Strada
San Francisco, CA —  June 24, 2011 2:49am ET
Bravo to you and the Wine Spectator for your blog.

Wine lovers all should read and take this piece to heart. Someone like yourself who opens wines closed in screwcaps all the time knows that the presence of reduction is very rare, and when it occurs, as you note, is not caused by the closure.

And as for oxygen ingress, Richard Grant Peterson, PhD, said it best when he wrote "Show me a cork that breathes and I'll show you a bottle of vinegar."

I look forward to reading in the future your commentary that makes it clear that anyone serious about producing a wine meant to age well, in particular a red, should close it under screwcap. The thinking that screwcaps are only for soon to be consumed whites is so limiting and misguided.

Much has changed in ten years in terms of the benefits of screwcaps and consumer understanding and acceptance of this . I now get annoyed when I am faced with a bottled closed in cork, and downright unsocial when the closure has ruined the wine
Phillip Dube
South Florida —  June 24, 2011 5:05am ET
Harvey -

I'll be very interested to read the OSU paper as some other reputable organizations have found contrary results. I speak primarily of the Australian Wine Research Institute which is an industry research group for an Australian wine industry that has firmly planted its flag in the screw cap world (little need for cork screws down under). A quick google search will show their results. Also Alan Limmer has published a great piece (somewhat technical but with plain language summaries) in The Australian & New Zealand Grapegrower & Winemaker magazine explaining the potential chemical processes at work in which mercaptans (really smelly things) and dimethyl disulfides (less smelly things) are involved in a redox reaction in the bottle.

But in the end its these kind of debates that move science forward.

I love and prefer screw caps. Even if reduction is an issue, I would still rather risk some instances than roll the dice with faulty corks and TCA. That said, we should keep an open mind that while screw caps may be better they may not yet be perfect.
Franco Meloni
South Florida —  June 24, 2011 7:40am ET
I have to say I am 50-50 on the subject. Being in the hospitality industry 9 out of 10 times when i twist a wine bottle open that is red, the customer lets me know of the disappointment. In the hospitality business you have a romantic tradition with wine and corks. The show is important in a way. As much as I enjoy proper wine, I still enjoy the art of the showmanship of opening up a wine with a cork!!! I would rather the industry focus on the newer corks out there that have synthetic liners on each end of that natural cork that do not allow wine to touch the cork. Thus preserving the wine and keeping the history.
Harvey Steiman
San Francisco, CA —  June 24, 2011 11:19am ET
Philip, one of the chemicals the Oregon State study looked at WS methyl mercaptan. The found exactly the same level in the wines bottled under cork.. If the wine has it, it got there in winemaking, not after bottling, according to this study.
Harvey Steiman
San Francisco, CA —  June 24, 2011 11:23am ET
The only cork product that seems to be getting unanimous or near-unanimous support from those who have tried many alternate closures is the DIAM. It uses a patented process to shred natural cork, cleanse it of potential TCA and assemble the shreds into a bottle-cork shape. It looks and behaves like a normal cork with only very rare incidences of TCA in the finished wine.
Ronnie Sanders
Philly —  June 24, 2011 5:23pm ET
We have a few producers who have been using Diam corks for some time now and with no issues. Its a great alternative closure to true cork.

Vince Liotta
Elmhurst Illinois —  June 25, 2011 11:23am ET

You are absolutely correct. Many are still prejudiced against screw caps. And at the risk of putting words in Harvey's mouth, this is why he continues to pursue this topic.

I really like screw caps (although I'd also like to see more development of glass stoppers as a more elegant option). I've recently enjoyed some of the first Australian and German Riesling producers efforts with screw caps from the 2002 and 2003 vintages, and find the results exciting. The fruit flavors are undeniably fresher and more vibrant than they would have been with a cork closure, even becoming more tropical, more exotic. The petrol character which often developed with age under a cork closure is less pronounced if apparent at all, and I must say, as much as I felt it added complexity in the past, I really don't miss it.The best part? The trademark finesse for which there is no substitute but bottle age is splendid.

Screw caps are really easy to open too!

Harvey Steiman
San Francisco, CA —  June 25, 2011 12:56pm ET
Thanks for your comments, Vince, and while I certainly favor the use of twist-offs or glass closures for all wines, my main focus is to try to bring sanity and reason to the discussion. Provable facts matter.

As for petrol: One of the chemicals the Oregon State study tested was linalool, a key aromatic component of Riesling and Gewürztraminer. When linalool oxidizes it develops a kerosene character, what we sometimes identify as petrol. Indeed, screw caps prevent that from happening so easily.
Brian Loring
Lompoc, CA —  June 25, 2011 1:26pm ET
Keep up the good work, Harvey! I look forward to the day when we all look back at discussions like this and wonder why anyone ever fought against screwcaps.

We're about to bottle our 7th vintage under 100% screwcap. We LOVE them. Our older stuff under screwcap is doing great. And the wines are aging :)
Jamie Sherman
Sacramento —  June 27, 2011 6:37pm ET
Appreciate all your blogs on screw caps. Science should lead us ultimately to the answer and we just need to put our pre-conceived notions and romanticism to the side for awhile. I still refer to the blog "The Real Problem with Corks" on the reliability of aging under screw cap all the time. Ageing wines is risky business under corks but putting some reliability behind aging as per the screw tops really would put my mind at ease. If I could buy all screw top, I would.
Don Rauba
Schaumburg, IL —  June 29, 2011 11:05am ET
Ditto on nearly every Pro-Stelvin/ScrewCap comment above. However, I disagree (half way) with one of Harvey's statements "Provable facts matter". Yes, to me, they do. But it's clear from the objections from the "pro-cork" side that facts aren't important at all! It's the "romance" of the cork for them! Maybe that's the key to winning this seemingly endless battle to eliminate TCA: appeal to their emotions, the way it's done in politics. (Groan)
Community Food Coop
Bellingham, Wa. —  July 22, 2011 2:39am ET
After tasting a brilliant 2004 Domaine Laroche Les Clos Chablis with a screwcap enclosure not long ago I cut the cord with the cork romance. This wine had an incredible vibrancy of fruit and mineral and yet it had all the integration that age imparts. It drank even better the second evening. Also, I recently had a screwcapped 2004 Wolf Blass Gold Label Chardonnay, a twenty dollar wine mind you, that was still stunningly lush and vibrant. Mr.Steiman himself, in 2005, gave this wine a score of 89 and concluded "drink now through 2007". I questioned if this wine had even peaked yet. Neither of these wines seemed to have any "reductive" qualities. I've tasted a few moderately aged rieslings under the cap as well and was equally impressed. I guess it's time to track down a few elderly reds with these enclosures and see how they are developing.

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