The problem of cork taint, estimated to effect somewhere in the vicinity of 3-5% of all wines sealed with natural cork, has long been a serious concern amongst winemakers. Hence, the drive for the wine industry to come up with a better closure for their wines.

Trichloranisole or TQA, the offending compound, occurs when corks are infected with a fungus in the bark or during processing of the cork. Levels of TCA are detectable by the human nose around 4 parts per trillion and typically imbue the wine with mouldy or musty aromas and an associated bitter and unpleasant taste.

Whilst cork companies worldwide are working overtime to come up with methods of negating or removing the incidence of TCA, and have indeed made significant advances, the wine industry has already moved in a direction away from natural cork. In recent times we have witnessed the emergence of the synthetic cork, made from supposedly inert silicon and adopted by many winemakers.

The aim of the silicon is to provide an altogether better seal that excludes oxygen, thereby slowing down the ageing process occurring inside the bottle and removing any chance of cork taint. At the time, such words sounded like manna from heaven to winemakers.

Preston Peak, along with many others, got caught in the hype, and some of you can remember the enthusiasm with which we espoused the new technology. With 20/20 hindsight it now seems that the industry adopted this new technology with scant regard of the need for long-term scientific study. To our dismay, we discovered too late, that not all synthetic corks are created equal.

Our story involves a gold medal winning Chardonnay, sealed with the latest silicon closure that rapidly and consistently deteriorated at an amazing rate. Thinking that this had been some fault of our own, that the kid gloves had fallen off somewhere and been replaced with clumsy, oafish, rough ones, we blamed ourselves.

Finally the truth came out, the synthetic cork had accelerated the ageing of this wine via the mechanism of the silicon absorbing free sulphur dioxide from the wine, thus leaving insufficient sulphur dioxide in the wine and opening the door for rapid and uncontrolled oxidation. I hasten to add that these problems occurred with the early synthetics.

Since then, the synthetic cork industry has been working hard to iron out these problems and many big name winemakers continue to use silicon corks, indicating their faith in the product. Nevertheless, once bitten, twice shy...

Now lets roll the clock back to the 1970's when the likes of Pewsey Vale Riesling started to use what became known as the Stelvin, or screw top. Apart from looking like a cheap sherry bottle, the Stelvin had many advantages over a cork. The wine kept fresher for longer, owing to a complete seal from the closure, the bottle could be cellared upright (no cork to keep wet), and there was no chance of cork taint. Of course, it is not possible to exclude all oxygen from wine, indeed all wines go to bottle with some level of dissolved oxygen, but since no air can get through the Stelvin closure (as opposed to a cork where oxygen is transferred slowly through the cork) the ageing process is dramatically retarded.

After 30 years of Stelvin, the consensus within the wine industry is that the closure works just fine. A couple of years ago I was privileged enough to taste a brace of aged Rieslings. The wine with the Stelvin was delightfully aged, crisp and delicious. I can't say the same about the wines bottled with a cork.

Obviously, the Stelvin, by virtue of its consummate sealing abilities, is well suited to fresh, aromatic white wines, such as Sauvignon Blanc, Riesling and Verdelho. Of particular note is Southcorp's decision to bottle all of its 2002 Rieslings with this closure. Preston Peak has decided to follow suit and do the twist as well with the 2002 Leaf Series whites in the Stelvin closure.

But what about reds? Grossets Wines in SA now bottle all of their premium red into Stelvin.

Jeffery Grossets, an Australian Wine Maker of the Year, sees only positive results from Stelvins stating that all beneficial aging of wine, including reds, occurs with little oxygen. Perfect cellar conditions may reduce the ingress of oxygen past the cork, but cork taint may still spoil the wine. Jeffery claims wine sealed with a Stelvin will age better for longer.

Preston Peak recognise that Jeffery has a strong argument. However, there is still the problem of consumer perception, the main reason why Stelvins fell from favour in the early days.

The Stelvin is not the most attractive of finishes; indeed it has connotations of cheap sherry and bad evenings with a deck of cards. It doesn't go "pop" when it's opened and it erodes a large part of the mystique of wine culture; the gentle extraction and examination of the cork, the prestige of the wine drinking experience, both traditions are lost with a screw top.

But remember, it's what's inside the bottle that counts. Through continuing wine education, I'm sure the Stelvin will have a bright future indeed, that is precisely what is worrying the cork companies.