OXYGEN BRINGS NEW LIFE TO CLOSURE DEBATE

The chemistry of winemaking and wine development is complex and not fully understood. However, it is clear that oxygen exerts a significant influence during most if not all stages of the process. In particular, the availability of small but controlled amounts of oxygen appears to have a beneficial impact on the long-term aging of fine wines. Some good progress is being made in determining the reasons for the importance of oxygen and identifying the many factors that can enhance or dilute its impact—including the closure. Claims of 1000-fold variability in the oxygen transmission rates of natural cork-based closures have been shown to be in error by more recent OTR studies and careful analysis of the results of various closure trials. The phenomenon of ‘random oxidation’ is increasingly acknowledged as being the result of a range of bottling line factors rather than solely due to the properties of cork closures. However, more research is required to improve our ability to control these factors in the way that modern winemaking demands. As closure research and development projects increasingly focus on the role of the closure in the development of wine in the bottle, it is timely to consider some recent results in the context of the overall importance of oxygen at all stages of winemaking.