The image... shows the state of 14 bottles of white wine sealed under various closures 125 months (just over 10 years) after bottling. This closure trial was conducted by the Australian Wine Research Institute to assess the relative effects of cork, plastic and screw cap closures on bottle-aged wine and has unequivocally shown the superiority of screw caps in aging wine.
It is well known that screw cap closures eliminate cork taint (TCA) and premature oxidization, but what this trial reveals is the fact that wine does mature/age in the bottle over time under screw cap. This is the most misunderstood aspect of the closure debate. Australians have been conducting both red and white wine screw cap trials for 20-30 years, so experience tells us this is indeed the case, but this is the first trial on such a grand scale to highlight this little-known fact.
...Thousands of bottles (of otherwise identical wine) were sealed with 14 different closures, including multiple natural and synthetic corks as well as one sample under screw cap.
The bottled wines were systematically analyzed over a 10 year period by sensory and analytical methods and photographed (you can see the sequential photographs below). The bottle sealed with a screw cap is positioned on the far left. While the pictures tell a convincing story, leaving little doubt as to which seal provides the most effective method of preserving a wine, it is the sensory evaluation results that are most revealing. The wines sealed under screw cap were still drinkable and showing appealing secondary aged characters while retaining freshness.
...there was huge variation in the results for the synthetic and cork closures, which was of more concern than TCA taint.Like most folks I tend to think of screw top wine bottle as being the cheap stuff we drank in college, if, that is, we drank wine in college.
The biggest issue for any form of cork closure is variability, the wines sealed with screw cap were extremely consistent bottle to bottle and no other closure achieved results even similar.
Most of the wine sealed with closures other than screw cap were completely undrinkable, some synthetic corks didn’t even last 28 months.
The study was initially established to determine which would be the best performing cork and we didn’t expect screw cap to be much of a factor. It didn’t take long to work out that it was going to be the most reliable performer, and as it turns out the results are emphatic.
In addition to cork taint, there is also concern about supplies of natural cork, which is desirable for many uses besides sealing wine bottles if I could afford cork flooring!--but the harvesting of which has caused severe damage to the cork forests of the Iberian peninsula, with subsequent impact on the related wildlife.