If you are a wine lover, you might have noticed an increase of screw cap closures for your wine bottle in the shops. The reason for this shift from cork to metal is that an increased amount of wine is being contaminated by cork taint, leaving the wine tasting musty and dull. The culprit for this unpleasant phenomenon, which can spoil up to one in 10 bottles, is trichloroanisole (TCA), a compound formed when chlorine used for bleaching reacts with mould already growing in the cork. Humans are incredibly sensitive to the compound and can detect it even at weak dilutions of six parts per trillion. TCA can flourish in several areas of a bottling facility, such as drains and barrels, but corks pose the biggest problem.
The problem of tainted corks is thought to be on the up because cork manufacturers are finding it increasingly hard to find supplies of good quality cork to meet demand – more wine than ever is being sold in bottles, rather than in bulk form. Looking further afield from a production perspective, an enormous number of screw top bottles are already produced for spirits and fortified wines, so a change to bottling wine with screw caps should not pose any problems, and in fact may be easier.
Screw cap closures consist of an aluminium cap with threads which fit the neck finish of a bottle and a liner of plastic (often PVDC), cork, rubber, or other soft material as wad to make a seal with the mouth of the bottle. While they can form a very tight seal, there is debate as to the extent of reduction and is one factor that limited the use of plastics and screw caps in the past. Reduction which results from too little oxygen being present during winemaking and aging, increases the presence of unfavourable sulphur based components that cause an odour of rotten eggs.
Oxygenation is also the subject of debate among wine producers who believe that oxygen is able to gradually seep through cork and into the bottle, and that this is the only way wine can mature. In this sense, screw cap producers argue that wine is aged by oxygen in the wine itself and a tiny amount of residual air held between the cap and wine.
Although screw caps seem to increase in popularity, only some wine producers are switching from cork to aluminum caps. Traditional French wineries do not seem to start bottling their premium Bordeaux wines with screw caps, but if so, then we will know the wine world will be really changing. Tell us your preference and if you notice any difference between cork wine bottles and screw cap ones.
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Source and photo credit: bestinpackaging.com, azom.com, winefolly.com, youngberghill.com, parade.condenast.com, Wikipedia, corkdiaries.com, divinediversion.wordpress.com
Camilla G.//SMC Editor
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