Oxygen permeability of closures
The closure plays a significant role in oxygen transmission during the period of storage of the wine. In a three year study carried out by the University of Bordeaux, France, the entry of oxygen was quantified for natural cork stoppers, technical cork stoppers, synthetic stoppers and different aluminium caps using a non-destructive colorimetry method. The results demonstrate that the different types of closure have significantly different permeability to oxygen. The screw caps (Liner Saran-tin) are hermetic and do not allow the entry of oxygen into the bottle over time. Synthetic closures allow the significant and constant inflow of oxygen from the time they are placed in the bottle.
Cork stoppers are between these two oxygen performance extremes. The different types of cork stopper perform differently, depending on the type. Specialised cork stoppers allow a small amount of oxygen to enter during the first month after bottling. Natural cork stoppers allow for a significant increase in the amount of oxygen in the bottle in the first few months, followed by a period of decreasing oxygen inflow until about one year is reached, after which the inflow of oxygen becomes negligible.
This study also concluded that storing the bottle in a vertical or horizontal position has little impact on the inflow of oxygen for the various closures. These results are in line with the data published in 2005 by Skouroumounis et al. This investigation was carried out over five years and demonstrated that wine storage did not have any effect on the composition and sensory properties of white wines.
A recent study of the performance of different closures on the development of a Sauvignon Blanc, in the bottle over two years, showed that from a sensorial perspective the development of the wine was balanced with the cork closures. The bottle with synthetic closures produced the most developed wine and it presented hints of reduction with Saran-tin screw caps, presenting better development with Saranex.