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Screw tops have been called into question as wine buffs found some bottles that smell of rotten eggs. From demijohns in rustic garages to the finest cellars, storing wine remains an unpredictable science - so what's the solution?

In good news for those who dislike tussling with corkscrews, screw-tops have been hailed as the answer to sealing off wine - cheap, hassle-free and a safe alternative to corks. They unscrewed a world of wine buying and storing snobbery.

But, amid a whiff of sulphur, the all-stopping properties of screw top wine bottles have been called into question.

Tasters at the International Wine Challenge, testing thousands of bottles of wine, found a small proportion - 2.2% of 9,000 bottles - smelt not of a pleasant bouquet of fruit and grasses, but of sulphur.

How to keep it?

The problem comes because the sulphides, used in wine as a preservative, are kept in by airtight screw tops as they break down into thiol - which gives the eggy smell. Corks, however, allow a certain amount of oxygen in to the bottle to neutralise them.

More than half of wine bottles sold in the UK each year now come with a screw cap. Many producers have switched in the past decade because of concerns about the reliability, and relative inconvenience, of cork.

Drinker

At wine-o-clock, does the seal on the bottle matter?

It is the latest twist in the unpredictable science of storing wine - a science that is especially important in a multi-billion industry, where investment in bottles to store is key alongside consumer sales.

So does the newly-sniffed out problem spell the end for screw caps and a search for something new?

Certainly not, says wine expert Malcolm Gluck, the future is still screw cap.

Like the straight banana, anti-Europe brigade, there is a cork lobby in the wine industry keen to seize on any hiccup, he says.

"It's rubbish," he says. "Any bottle can suffer from sulphidisation." Sulphur is added to wine as a preservative - without it, open wine would turn brown just as a cut apple does. "Even organic wines have to have sulphur."

The problem lies, he says, with a minority of producers who have not yet got the level of sulphur right, when wine is sealed with a screw top, rather than a cork, which allows a small amount of air in over time.

Say what you smell

And the argument that corks are better for storing wine over a long period? That valuable bottle of fine red you want to lay down?

"I would say the opposite is true," says Gluck. Screw top wines can be kept for longer before they mature. The effects of stopping the end of an ageing bottle with a cork can differ from bottle to bottle - "and it's not always a congenial difference".

It's more important to store the wine at the right temperature and away from light - hence cellars. And to decant it before drinking.

Tetrapaks

Next, picnic-friendly Tetrapaks

But humble quaffers should also have the confidence to speak up when the wine is off, even if the waiter is removing a modern screw cap with a flourish, says Guy Woodward, editor of Decanter Magazine.

"It's important that consumers are aware of the possible problems and they shouldn't be afraid to question a bottle that they've bought - especially if it's in a restaurant where they're probably being overcharged anyway."

But, as he points out, at 2.2% of the bottles tested, the problem affects about half the number that tend to be corked, 5%. And that proportion was picked up at the wine fair, by buffs who "could smell a rotten egg at 50 yards".

As for the future answer to fault-proof packaging and storing wine, for those who baulk at a screw top, there is more to come.

Tetrapaks for wine were tried 10 years ago and didn't catch on, but the market may be ready to accept them now, says Gluck. And why not? They are a food approved container

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