The Australian wine research institute had undertaken a study to compare the performances of different types of stoppers. Bottles were filled with a Semillion wine in May 1999 and sealed with 14 different stoppers: metal screw-cap; two types of standard cork; two types of technical cork and nine plastic stoppers. The physical modifications of the stoppers, as well as the chemical and sensorial changes in the wine were analysed periodically over a period of 20 months. The results demonstrated that the majority of the stoppers were better suited to short term storage (60-12 months) rather than long term storage. Beyond this period, there is loss of sulphur dioxide, browning and oxidation. According to the Institute, bottled wine sealed with a metal screw-cap retained the best concentration of SO2 and ascorbic acid, and also had the lowest rate of browning.
