Impact of compression on the gas permeability of cork stoppers

Abstract

Oenological closures play a crucial role in the preservation and evolution of still and sparkling wines in bottle. Approximately 21 billion stoppers are produced annually for the global wine industry with 13 billion being cork-based, originating from the bark of cork oak tree (Quercus suber L.). In fact, a gradual and minimal entry of oxygen and conservation of effervescence in the case of sparkling beverages play an essential role in wine ageing. Therefore, the mechanical reliability of these stoppers is not simply a matter of tradition or appearance, but a crucial factor in maintaining wine stability and supporting proper ageing. Cork stoppers are compressed to seal both still and sparkling wines. However, the exact relationship between the level of compression and the resulting gas barrier efficiency is not yet fully understood. For still wines, stoppers typically undergo a 23 % diameter compression (40 % volume), while sparkling wine stoppers reach a 40 % diameter compression (70 % volume). Current research indicates that for still wines, these compression levels have little impact on oxygen transfer. However, the much higher compression used for sparkling wines may play a more significant role in gas barrier efficiency and wine preservation. This study examines the gas permeability of still and sparkling cork stoppers at diameter compression levels ranging from 0 % to 40 % of their original size, aiming to characterize the relationship between deformation and the resulting gas barrier performance to establish the compression level at which the gas transfer rate (GTR) becomes stable enough for wine preservation. Using a manometric gas permeability device developed in-house, GTR measurements were conducted on stoppers to determine their intrinsic material permeability according to the compression level and subsequently within glass bottlenecks to evaluate the specific contribution of the cork-glass interface.[1] This research distinguishes between the permeability of the cork itself and the quality of the cork-glass interface. These findings help define the optimal compression needed to protect wine quality. This study offers a scientific basis for improving current bottling practices and understanding how cork performs under pressure.

References

1. Chanut, J., Bellat, J.-P., Gougeon, R. D., & Karbowiak, T. (2021). Controlled diffusion by thin layer coating: The intricate case of the glass-stopper interface. Food Control, 120, 107446. https://doi.org/10.1016/j.foodcont.2020.107446