Are screw caps an improvement?
Take all the good stuff you’ve heard about screw caps with a large grain of salt. The “perfect seal” hasn’t delivered fault-free wine as promised. So far, all scientific studies on wine closures have shown a definite linkage between screw caps’ near oxygen-free environment and negative sulfide reduction. Real-world evidence also suggests much higher fault rates than advocates let on. The culprit is not screw caps per se but rather their tightly sealing tin or foam liners.
A lot of commentary on screw caps turns out to have been overenthusiastic cheerleading for an underdeveloped, unproved technology. Add in loads of ill-informed, wishful thinking, often lacking any firm foundation in science, and the picture’s not pretty. To put it bluntly, from the start, screw-cap advocates botched their wine chemistry badly. Wine, it turns out, needs a tiny amount of oxygen after bottling (similar to what corks let in) to prevent the development of smelly aromas, off flavors, and coarseness on the palate. Screw-cappers, long in denial about this possibility, are now reaping the consequences.Unfortunately, far too many wine writers and wineries jumped on the screw-cap bandwagon prematurely and have turned a blind eye to its shortcomings. With reputations and potential recall liability at stake, it’s doubtful they’ll be drawing attention to screw-cap inadequacies soon.
Space restrictions here limit any explanation of the extremely complex chemistry concerning sulfide-reduction faultiness under screw caps. (Please refer to my articles in Harpers, Decanter, or World of Fine Wine and to George Taber’s excellent book, To Cork or Not to Cork.) Instead, let’s focus on methods for identifying sulfide reduction that provide consumers, retailers, and sommeliers with a means to protect their cellars.
Although no less damaging than TCA (trichloranisole, which causes cork taint), postbottling sulfide reduction is much more difficult to understand, identify, and explain. At obvious fault levels it dominates wine aromas with progressively stinkier, sulfurlike notes (struck flint, cabbage, rotten egg, garlic, hydrogen sulfide . . .). Before this point, not unlike prethreshold cork taint, it gradually shows a suppression of pure varietal expression, blunting of fruit, shortening of length, and coarse astringency on the palate.
Now here’s the tricky bit: predicting negative sulfide reduction beforehand is, at best, a lottery because every vintaged wine has a unique—and unmeasurable—tendency for reduction, called its redox potential.
Although screw-cap advocates have proposed fining with copper sulfate as both a preventive and curative measure for potential reduction, established sulfide chemistry indicates this only knocks back symptoms temporarily, and reductive characters are likely to return after bottling. Far from being wine friendly, copper fining aggressively strips away both good and bad sulfides, which determine “typicity.” Also, copper sulfate is considered a toxic heavy metal—not very consumer friendly.
Copper, however, offers a reliable means to gauge how sulfide reduction is impacting a wine. Pour two glasses; then drop a pure copper wire into one (avoid alloy coins) and swirl. If the coppered wine becomes more aromatic, fruitier, and smoother finishing, then ask for a refund. An exchange will simply redeliver the problem.
Stinky Time Bombs
Sommeliers, retailers, and consumers should be very wary of wine that won’t be consumed within six months to a year after bottling (studies indicate reduction appears around one to one and one-half years, although redox suggests it can happen earlier or later). Take care with sulfide-rich wild-yeast ferments and lees aging and varietals traditionally prone to reduction (e.g., Dolcetto, Pinotage, Syrah, Sauvignon Blanc). Undoubtedly there are plenty of screw-capped time bombs dating back to 1999 ticking away in cellars. It’s worth double-checking wine stocks every six months; wines I’ve recommended have gone over to the dark side when tasted a year later.
The fact that manufacturers are furiously attempting to develop new oxygen-permeable liners should be evidence enough that today’s screw-capped wines have serious issues. Ironically, screw-cap advocates Down Under jokingly refer to sulfide-reduction faultiness as “screw-cappy,” failing to realize that some consumers have changed the term to “screw-crappy.” Chateau Yellowstone, anyone?