Definition: corking, new methods

Nevertheless, screw caps, for example, are becoming increasingly popular around the world. In this regard, the renowned Chablis producer Domaines Laroche is a pioneer in this famous region, passionate and active in the use of this type of closure.
A recent experiment at Laroche compared Chablis wines from the same vat, one sealed with a screw cap and the other with a traditional high-quality cork. The results were unequivocally in favour of the screw cap, which produced a much fruitier wine than the cork version. This is not the first time this has happened, as experts who have already carried out the same comparison have invariably found that, among many producers, wines sealed with screw caps are fresher, fruitier and have better defined aromas.
Detractors will argue that this is nothing more than propaganda against the traditional cork, which has proven itself over centuries of use.
What is it about the capsule that upsets so many wine lovers? Of course, these "traditionalists" cannot do without the corkscrew, which we understand. Others find the aesthetics of the capsule and the neck of the bottle with its screw thread too industrial, which we also understand.
But the fact remains that screw caps work wonderfully well. They preserve all wines with a higher degree of freshness than any other system. We dare to say this more than ever.
What does it take to achieve this? Producers who switch to screw caps must follow slightly different winemaking techniques to prevent their wines from developing sulphite characteristics, which result in rubbery or burnt matchstick aromas. Such odours have occurred in bottles sealed with screw caps. These same producers now know how to use these winemaking techniques for both white and red wines. The unchanging slogan is: "What you put in the bottle stays intact in the bottle"!
Leaving aside public opinion on screw caps and cork stoppers, a recent study by the oenology faculty of Victor Segalen University in Bordeaux has just been published in several languages in the wine world (2007):
"The key factor for screw caps, as for any other type of closure, is their degree of oxygen permeability."
This is precisely what the French researchers examined. They studied the kinetics of oxygen infiltration with natural cork, synthetic stoppers of all kinds and screw caps over a period of three years. The subtle element of this research was for the researchers to determine the oxygen content entering the bottle without having to insert anything inside. To do this, they used a sensitive solution that changes colour when it comes into contact with oxygen. The different levels of oxygen penetration can thus be measured accurately using a colourimetric scale.
What did they discover?
1. That synthetic corks all have the highest oxygen permeability.
2. Natural cork has an average level of oxygen permeability.
3. Cork of the highest quality allows less oxygen through than cork of average quality.
4. Surprisingly, the latest generation of screw caps store more oxygen than all other closures simply because of the volume they occupy in the bottle. The vacuum created by the cap is undoubtedly greater.
Not satisfied with these results, the researchers then measured precisely, once the screw cap was in place, the permeability of a screw cap allowing a low but steady supply of oxygen, with insignificant differences between the various cap manufacturers.
Another important factor emerged during the study, which was to investigate the effects of the position of the bottles: upright or lying down. This latter factor was found to have very little influence on oxygen ingress over a period of the first 28 months. The authors even noted that vertical storage ensured 100% humidity inside the bottle, which also allowed the cork to absorb maximum moisture, contrary to the popular belief that advocates maintaining high humidity in the cellar of any discerning wine lover! In fact, humidity in cellars is important for wines stored in wooden barrels or casks, but not really for bottled wines.
The conclusion:
Screw caps allow the least oxygen to enter, natural cork is average, and synthetic closures are the worst, absorbing the most!
So if you produce a great white wine, like Michel Laroche in Chablis, and your winemaking techniques favour low oxidation, such as screw caps, then screw caps are the answer!

Source: Wine Spectator 31.10.2007 – Matt Kramer "Seeking closure" – Translation and adaptation by Philippe Margot.