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Plastic Fantastic

Synthetic stoppers provide a few of the answers to natural cork's drawbacks. ROSE MURRAY BROWN MW asks why New World producers are going plastic.

Peel the capsule off a bottle of UK supermarket own-label or a large scale New World producer’s wine. You are more likely to find a multicoloured plastic stopper lurking underneath, than a natural cork. Synthetic stoppers are now considered to be more effective in protecting freshness and flavours in fast-moving, lower-priced wines, than low-grade natural corks. But when it comes to stoppering wines designed for long ageing, winemakers are showing understandable resistance in using an unproven piece of plastic. It’s almost a decade since the first synthetic cork appeared. Since then, they have improved dramatically in effectiveness, reducing leakage and oxidisation problems. They have proved to be useful seals for vin de pays drunk within one year. They are used by more than 300 wineries worldwide and now stopper 5% of wines we buy. But, synthetics are not as sophisticated or advanced as we might think. The impetus for change from natural cork first came from UK supermarket buyers, frustrated by the TCA cork taint. Recently, taint rates were quoted as low as 0.67%, but talking to Australian firms, BRL Hardy and Southcorp, in reality it’s more like 5%. ‘Even if it’s 0.67%, someone is opening a tainted wine every 25 seconds,’ says Richard Gibson of Southcorp. Whatever today’s rate is, the switch to synthetics has benefited some. ‘We noticed a dramatic fall in complaints when we moved to synthetics,’ says Sainsbury’s Justin Howard-Sneyd MW. But, he adds, no closure is problem free.

Pull the corks from 10 wines worth £5 – you will notice the variation in synthetics: different polymers, densities, inert materials and manufacturing methods. Brand leader, USA’s Supremecorq, which sells 100 million stoppers a year, uses ‘injection moulding’ (as do Australia’s Integra and Aegis). Its outer skin seals the closure ends exposed to wine, protects the internal cell structure, resisting wine absorption. It’s solid, won’t chip or crumble – and wine can be stored upright. Neocork, which claims to be the first synthetic cork designed by wineries (Mondavi, Kendall-Jackson, Clos de Bois) for wineries, is made by extrusion. It’s made in a long sausage, then cut up – claiming a microcell structure is more even and dense than moulded ones. Made from two different materials, it works like a gasket with seal-to-bottle walls. To the untrained eye, it looks similar to moulded versions. UK-made Betacorque looks more like cork. It claims, like others, to be impervious and non-absorbent, but exhibits a minute porosity to gases and water vapour, allowing cork ends to take up wine aroma, and claims to be easier to extract and re-insert. Partially synthetic corks, made from cork particles and synthetic symmetrical microspheres, like Sabate’s Altec are popular with Skalli and Louis Latour, but Sichel claims Altec causes oxidisation problems – and Rex Hill in Oregon and Zaca Mesa in Santa Barbara complain of TCA taint and ‘glue poo’.

Peter Godden of AWRI (Australian Wine Research Institute) has studied synthetic closures and found little difference between the five major brands. ‘One area in which they differed was in physical measures of extraction force (both peak and energy force) to remove from bottle and corkscrew,’ says Godden. This problem is seen as synthetics’ major inconvenience, with their different elasticity to natural cork, a waiter’s friend is more effective than Screwpull. Extraction is one problem – another is plastic taint. There is no evidence that this exists, but it has put some producers off. Stephanie Toole of Mount Horrocks dislikes plastic, she recently spearheaded 15 Clare Valley Riesling producers’ switch from natural cork to Stelvin screwcaps. ‘I believe plastic is not suitable for premium aromatics,’ says Toole who, like Louisa Rose at Pewsey Vale, has been testing Stelvin for 20 years. Peter Godden agrees with Toole that screwcaps performed better in trials at retaining SO2 (sulphur dioxide) compared to synthetics. They might make a better seal – but there is consumer resistance against screwcaps.However, the ‘hot’ issue today with alternative closures is ageing. Many believe a tiny amount of air passes through or around a natural cork, allowing gradual oxidative ageing, which synthetics’ tight fit do not allow. But there is no lasting research to prove either way. Godden’s data at AWRI is only up to 20 months. A new development in the age issue is the launch of ‘Preservera’ from leading synthetic manufacturer, Supremecorq. Designed for longer ageing, it is based on the fact that the rate at which wine oxidises in bottle is the rate at which SO2 is lost. By using technology from the soda industry, they have added ‘food-grade’ sodium metabisulphite to Preservera stoppers to replace molecular oxygen and improve anti-oxidative properties. ‘Results showed it to be more effective than high-grade natural cork in maintaining free SO2 levels,’ says Supremecorq’s Joyce Steers-Greget. Southcorp, BRL Hardy, St Francis and Errazuriz are experimenting with it, but would not comment on performance. Costwise, it will be 20% more than their current supremecorqs – equivalent to medium/high-grade natural cork.

‘It looks like a logical step,’ says Godden. But a possible negative might be if an extracted closure is chewed by an animal or child. There seems to be enthusiasm from New World producers to try Preservera, but Old World producers are less interested. Even though top New World producers, like Rosemount and Mondavi, routinely check for cork taint and experiment with closures, most Old World producers do not routinely bottle test batches with different closures. Robert Joseph, of watchdog website www.corkwatch.com, believes synthetics will eventually rival screwcaps. He also agrees that not enough Old World producers are willing to test new closures. ‘But the biggest question may be oak-matured wines – we may be used to woody characters which derive from cork maturation,’ says Joseph. Like Godden, Joseph sees Supremecorq’s new product as a logical step. It could be a new generation in synthetics, but the real problem is that the results for long-term ageing are not known. So we will just have to wait and see.



‘It is absurd that we use natural cork for 90% of wines drunk within the first 6–12 months, when we could use plastic screwtops. It’s a waste of cork.’


‘For wine that will spend less than one year in bottle, cork is not necessary. And a good non-cork closure is preferable to poor cork. For ageing, my only experience was with Duckhorn Decoy 1995 that had a black non-cork cork in, and was in top condition when I opened the last bottle last year.’


‘My only problem with synthetics is with extraction (particularly using Screwpulls). It is shameful that none of the first growths currently test corks for taint. Mouton claim no need to test for cork taints based on the evidence of rarity of complaint.’

ADRIAN BRIDGE (Taylor’s/Fonseca)

‘We are looking at using synthetic corks, but are concerned about elasticity and higher costs. We have a low taint rate – below 1% – possibly because we can easily hassle the cork industry. My view on synthetics is that they are not taint free – but I know there is no real evidence to prove this.’

CHARLES SICHEL (Sichel/Coste Group)

‘We use Integra for four wines, with positive consumer feedback. Demand for synthetics is coming from all major markets. Synthetics will become widespread, but even if proved effective for long ageing, there is a considerable barrier from consumers of fine wines.’


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