Alternative wine closure

Alternative wine closures are substitute closures used in the wine industry for sealing wine bottles in place of traditional cork closures. The emergence of these alternatives has grown in response to quality control efforts by winemakers to protect against "cork taint" caused by the presence of the chemical trichloroanisole (TCA).

The closures debate, chiefly between supporters of screw caps and natural corks, has increased the awareness of post-bottling wine chemistry, and the concept of winemaking has grown to continue after the bottling process, because closures with different oxygen transmission rates may lead to wines that taste different when they reach consumers.

The cork-industry group APCOR cites a study showing a 0.7-1.2% taint rate. In a 2005 study of 2800 bottles tasted at the Wine Spectator blind-tasting facilities in Napa, California, 7% of the bottles were found to be tainted.

Synthetic corks are made from plastic compounds designed to look and "pop" like natural cork, but without the risk of TCA contamination. Disadvantages of some wine synthetic corks include a risk of harmful air entering a bottle after only 18 months, as well as the difficulty in extracting them from the bottle and using the plastic cork to reseal the wine.James Laube of Wine Spectator notes that some can also impart a slight chemical flavour to the wine.

Unlike natural corks, many wine synthetic corks are made from material that is not biodegradable but recyclable as either #4 or #7 (see resin identification code) in many communities. There are two main production techniques for synthetic wine closures: injection molding and extrusion (mono- and co-). Methods also exist which are claimed to combine the two techniques of injection and extrusion. A 2007 study by Victor Segalen Bordeaux 2 University showed that injection molded synthetic corks allowed the highest levels of oxygen permeation when compared to natural cork and screw caps, offering the lowest protection against oxidation of the wine.

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