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Screwcaps and ageing

Screwcap closures have had some bad press, but in my opinion, any wine destined to be drunk within a year of production should be sold in a screwcap bottle.

Ch.Margaux is carrying out trials with screwcaps

Ch.Margaux is carrying out trials with screwcaps

What is good about screwcap bottles

  • The closure does not contaminate the wine. The wine may still be corked because of contamination during wine production, but at least the screwcap won’t have caused it.
  • Every bottle will be the same as the next. There are some caveats, and you should refer to a previous blog for further details. Every natural cork is different, whereas every screwcap closure is identical.

What is bad about screwcap bottles

  • Removing a screwcap just doesn’t have the same theatre as removing a cork. Sadly, I can’t think of any solution to this problem.
  • Production of ‘reductive’ chemicals in the wine because air is excluded. These are sulphur compounds which may be produced in the bottle because of the absence of air. These compounds disappear quickly after a bottle is opened, but can be excluded by modifying the winemaking process.
  • A little bit of oxygen appears to be necessary for a wine to age gracefully. Original screwcaps allowed almost no air to reach the wine.
  • Screwcaps were associated with cheap wine, so producers of quality wine tended to shy away.

New developments

  • The seal in a screwcap is provided by padding at the top. Different materials are being used for this padding, which allow different amounts of oxygen to pass through. This means that they can potentially be used for ageing fine wine.
  • The obvious thing is to try long term tests, and some tests were initiated in the 1980s in Australia. However, the prestigious Ch√Ęteau Margaux in Bordeaux has started their own long term trials. Endorsement by one of the great old names in the wine business would make all the difference in the acceptance of screwcaps. Time will tell.

Conclusion
By choosing the correct seal, there will be screwcap closure for every wine, but it may take a while to prove the point.

Screwcaps versus cork for wine bottles

branded natural cork

natural cork

Natural cork provides a very good seal for a wine bottle, but a screwcap is potentially better still. There are pros and cons for each of them.

Sealing liquids

  • Cork has a unique cellular structure which allows it to be compressed, and then spring back to its original shape. This provides a very good seal to prevent wine from seeping out. It can still seep out if the bottle is overfilled, the cork damaged, or because of poor storage.
  • Screwcaps prevent any wine from seeping out.

    screwcap

    screwcap

Sealing gases

  • Cork. Oxygen can slowly diffuse through the cork into the wine. Some corks are more porous than others, and some have defects; this allows more rapid diffusion of oxygen into the wine, and more rapid ageing.
  • Screwcaps. The original screwcaps allowed almost no oxygen into the wine, and this may cause unpleasant odours to develop. Different seals are now available which allow controlled amounts of oxygen into the bottle.

Contamination

  • Corks can be contaminated with TCA, a very small amount of which makes the wine undrinkable. Refer to this earlier post for details. This is cork’s biggest disadvantage.
  • Screwcaps do not contaminate the wine.

Storage

  • Cork. Bottles have to be stored with the wine in contact with the cork. If not, the cork dries out, and becomes a less effective seal. Rapid temperature fluctuations can cause a cork to move within the bottle neck, which can also cause sealing problems.
  • Bottles sealed with screwcaps do not suffer from these problems.

Long-term ageing

  • Cork has been used as a wine closure for centuries, and there is plenty of evidence that a good wine, with a good cork, stored in a good cellar, ages gracefully.
  • Screwcaps have been around for decades, and there is evidence that some wines age well. However, plenty more trials will be needed over many years, before everyone is convinced.

Conclusion

The scientist in me says that a screwcap with the right seal, is the perfect closure. No bottles will be contaminated, and every bottle in a batch will mature the same way. My heart however, would rather see a cork pulled from a fine bottle of wine, rather than someone crack open a screwcap.