Until recently in winemaking history there was no debate about how to seal a bottle of high-quality wine. Cork had been the best choice for hundreds of years. Closures only became a hot topic when the suitability of cork was demonstrated to be an issue by the discovery of what causes “corked” bottles—2,4,6-trichloroanisole. Scientists learned how to measure this mold, and packaging companies subsequently rushed to develop alternative closures that were TCA-proof.
It turned out that eliminating TCA caused by closures was relatively easy. Wineries simply needed to switch away from stoppers made of cork, and voila! No more corked bottles. The TCA needed cellulose (a big component of natural cork) and exposure to chlorine (from cleaning solutions or tap water, usually) in which to grow.
Winemakers who had become royally ticked off at the high incidence of bad bottles began experimenting with screwcaps and synthetic stoppers. They eliminated all bad bottles due to cork taint but discovered other issues, including synthetics that allowed the wine to oxidize too quickly and screwcaps that made too tight a seal.
In the meantime, the incidence of cork taint dropped significantly among major natural cork suppliers, who have confronted the problem and taken expensive measures to correct it. In a sense, they have removed much of the original rationale for using non-natural cork closures. But during the years required to clean up the cork production business in Portugal and Spain, the makers of alternative closures also hustled to get the bugs out of their products, and they largely succeeded.
Multiple choice closures
Winemakers today find themselves with multiple choices in closures, and three different articles in this issue explore these options and their consequences. Winemakers can choose by price, by appeal to tradition, by TCA resistance and by a relatively new three-letter acronym.
The oxygen transmission rate (OTR) of a closure may become as important for a winemaker to understand as free SO2—and not just at bottling time. OTR expresses the amount of oxygen ingress in wine bottles from different closures. OTR is often expressed in micrograms (μg) of O2 per bottle per day.
As our contributor Jamie Goode explains in his report, “Post-Bottling Winemaking” on page 26, the choice of closure and its particular OTR may require winemakers to adjust their handling of wines from the crushpad to the bottling line, knowing that what they do along the way sets up the wine for its interaction with oxygen in the bottle afterward. This reflects a whole new variable for many winemakers.
The term, “post-bottling winemaking,” may be a misnomer, since it implies an active role by the winemaker at a time when the wine is long gone from the cellar. But it doesn’t take much imagination to grasp that a wine under a synthetic stopper with a high OTR is going to evolve much faster in the bottle than under a tight screwcap with a low OTR.
Effect on winemaking
One enologist actively grappling with this issue is Greg Kitchens, head winemaker for Don Sebastiani & Sons in Sonoma, Calif. Laurie Daniel interviews Kitchens on page 22 specifically about the wide variety of closures that his company uses—sometimes largely for marketing reasons—and how they affect his winemaking decisions pre-bottling.
A third article in this issue focuses directly on glass stoppers by interviewing winemakers in the Northwest and elsewhere who have chosen to use them. Peter Mitham reports on page 32 that a drop in price, a wider variety of bottle molds that accommodate glass stoppers and a very positive reception from customers recently has prompted numerous wineries to adopt this elegant-
Cork is not going away. The quality of natural cork is probably better than ever. Numerous surveys have shown that a large majority of wine consumers prefer cork for its evocation of tradition and believe that it’s the best seal to keep wine in good condition. But clearly, wineries have many options today when they bottle their wines, and natural cork is just one of them.
Smart winemakers should work with their marketers and use the latest research about OTR, combined with their own experiences to make the right decisions about winemaking vis à vis closure types. We think there will be no single, neat answer to the question of what is the best closure for a wine, but there will be plenty of information to help a winemaker craft the best wine for a particular closure.