Julie Harrison - Wine Closures

It was only 15 years ago when most New Zealand kitchens would have had a cork screw in the cutlery drawer.  Now if you take a bottle with a cork to someone’s home getting it open can be an issue.  

The closure on a bottle wine is there to keep the wine in and oxygen out.   Since the 1400’s cork has been used to make the closure and there are a number of very good reasons for this.  Cork comes from the bark of Cork Oak trees mostly grown in Portugal.  The cork is harvested from each tree every nine years leaving the tree intact and ready to produce a new batch of cork 9 years later, so it is a renewable resource. Cork is malleable enough to fit into the neck of the bottle then expands to form a barrier and has been proven to stand the test of time when aging wine.  Whilst it is there to keep the oxygen out cork does allow a small amount of oxygen in and this is believed to be a major part of the aging process  for wines that are made to last.

The main problem with cork is cork taint, which occurs when wine comes in contact with a chemical referred to as TCA (2,4,6-trichloroanisole) that can develop in cork. Very low levels of this chemical result in the wine having a musty, wet cardboard character.  It is believed that during the 80’s up to 10% of wines were affected and while this figure has come down significantly in recent times, due to the cork industry improving processes, it still affects around 2% of wine.  Variation between corks is also a problem. Corks are a natural product and can vary dramatically in their porosity, which in turn determines how much oxygen can get through into the wine.  Even within a case of wine, variations in each cork can mean different amounts of oxygen are getting into the individual bottles leading to bottle variation. As with anything you get what you pay for and wineries can opt to pay for more expensive, more uniform corks that are less likely to cause problems.

Screw caps began development way back in the 60’s but didn’t really take off until the early 2000’s.    Clare Valley winemakers in South Australia were becoming increasingly upset at cork taint ruining their delicate Rieslings and to overcome logistical issues decided to band together for the 2000 vintage to try out screw cap technology with good results.  New Zealand wine makers came on board not long after and screw caps now dominate the Australian and New Zealand Wine industries. Screw caps are able to protect the wine from oxygen with no risk of cork taint and result in wines that are consistent from one bottle to another.   They improve the preservation of aromas, flavours and freshness and are obviously easy to open.  The argument against screw caps is mainly aimed at wines that are designed to age over a number of years, as some people believe that the small amounts of oxygen coming in through the cork are vital in the aging process.  Others believe that wine under screw cap can sometimes become reductive which means when you open it there is a flinty/rubbery smell. New Zealand and Australian consumers have taken to screw caps very quickly but there is still some perception in other markets that a screw cap means a lower quality wine.   Screw caps are made of two parts, the cap itself and the all important liner.  The technology behind screw caps continues to develop  and screw caps are now available with a choice of oxygen permeable liners so winemakers can control the oxygen transmission rate, which covers the issue of oxygen being an important part of wine aging.

There are other closures available and one of our French suppliers is using the classy Vinolok system.  The bottle is sealed with a glass stopper which is leak proof and airtight and has no negative impact at all on the wine These are completely reusable and I reuse the empty bottles and closure for water, oil or vinegar.

Wineries often take a punt both ways and use screw caps for wines designed to be consumed early and keep their high end wines that are designed for longevity under cork.  In this case they will invest in top quality corks to minimise the risk of cork taint and variation.  Still when you purchase an expensive bottle of wine for aging it is heartbreaking to open it a few years later and find it tastes of wet dog.