Three closure tales

An aspect of wine bottle closures that is seldom discussed is there ability to protect the wine in less than ideal storage conditions.

The importer air-freighted control samples for comparison with wines in the container which were sealed with cork, Vinolock and screwcap.

I had a chance to compare the effectiveness of three different wine closures after a container of German riesling was affected by heat in transit to New Zealand.

The importer air-freighted control samples for comparison with wines in the container which were sealed with cork, Vinolock and screwcap. To see how each closure performed, read on.

Corks have a remarkable ability to form a tight seal in bottlenecks with variable internal diameters. (Photo: First for Women website)

Cork

Bottles are made by putting a blob of glass in a mould then blowing air into it so the molten glass splatters to the outside of the mould and forms a bottle which is perfect on the outside but can be misshapen on the inside. Corks have a remarkable ability to form a tight seal in bottlenecks with variable internal diameters. Squeeze a cork and it doesn’t ooze out the other way, it tries to spring back to its original shape.

On the downside, when wine heats up and expands it puts pressure on the cork and will eventually start to force its way out of the bottle. When the wine cools down it can draw air into the bottle. Too much air and the wine may become oxidised and unsaleable.

The German riesling under cork showed clear signs of leakage and oxidation. It was unsaleable.

Vinoloks are easy to remove and reseal with a satisfying click. (Photo: DuPont website)

Vinolok (also sold as Vino-Seal)

Vinolok is a sexy little glass stopper with an inert O-ring. It claims to create a hermetic seal that prevents oxidation. My experience with Vinolok has been very positive. They are easy to remove and reseal with a satisfying click. They are relatively expensive to buy and to package, although in my view they enhance the overall bottle presentation and look smarter than a screwcap.

When compared with control samples, the heat-affected Vinolok-sealed wines from the container did show some deterioration, although they were better than the wines under cork.

Screwcaps are the obvious choice if the wine is likely to be exposed to poor storage conditions. (Photo: Drinks Business website)

Screwcap

We could find no difference between the heat-affected and control samples. It is possible that the heat-affected wines may not cellar as well as the control samples, but that is sheer speculation and there was no evidence of any deterioration.

If that experience is a reliable indicator of closure resistance to heat, then screwcaps are the obvious choice if the wine is likely to be exposed to poor storage conditions. It is ironic that Asian countries around the equator, where heat damage can be a real issue, tend to have a conservative attitude toward closures, with many wine retailers preferring corks.

3 thoughts on “Three closure tales”

  1. Sam Martin says:

    Bob, do you think there was a chance that the bottles sealed with screwcaps were lower in the container? Is it fair to suggest wines at the top of the container may be more heat damage than those near the floor?

    1. Bob Campbell says:

      I was given no temperature data but you do make a good point. Position in the container does make a difference.

  2. Gillman Ken says:

    It is interesting to hear accounts like this from those who have been asked to assess shipments that have gone wrong: I remember an MW friend telling me a story like yours many years ago. These containers are normally monitored in detail for temperature – were you given precise temperatures and durations?
    Our individual experience, living in tropical North Queensland, accords with what you say above: we have a very strong preference for Screw Caps.

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