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.
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