Oxygen transfer and reactivity in a corked bottle during storage

Abstract

Oenological closures play a key role in wine aging by influencing oxygen ingress, enabling a slow oxygen supply that can favour wine maturation. This study aimed to improve understanding of oxygen transfer and reactivity mechanisms in a corked bottle of wine during bottle storage by identifying the different oxygen pathways and characterizing their kinetics from short- to long-term aging. To disentangle these mechanisms, the oxygen barrier properties of microagglomerated cork stoppers of varying lengths were investigated using a mini-bottle system over 18 months. Stoppers ranging from 6 to 42 mm were compressed into glass tubes (18.5 mm diameter, 70 mm length). The tubes were sealed under an inert argon atmosphere with a glass disc and stored either with or without 10 mL of a model wine solution to evaluate the influence of wine on oxygen transfer. Oxygen permeation was monitored by chemiluminescence during 18 months upon storage at 25 °C and 50% relative humidity. Several distinct transfer and reactivity mechanisms were revealed. The first corresponds to rapid oxygen equilibration between the gas and liquid phases of the model wine, occurring within approximately 15 days. Due to its fast kinetics, this mechanism can be neglected for long-term aging. A second mechanism involves the diffusion of oxygen initially trapped in the cork cells into the mini-bottle, resulting in a gradual oxygen increase. This process shows slow kinetics, lasting up to nine months in samples without model wine. In the presence of model wine, a decrease in oxygen concentration in the liquid phase was observed after four months, attributed to the extraction of phenolic compounds from cork and their reaction with oxygen dissolved in the wine. These processes also occurred over several months. Simultaneously, continuous oxygen permeation from the external environment through the closure system was observed, leading to a progressive long-term increase in oxygen concentration. Thus, cork closures mainly influence the oxygen concentration in the wine by initial oxygen release from the cork cells, chemical reaction of oxygen with the extracted phenolics, and long-term ingress of oxygen from the external environment. Better understanding of the kinetics of these overlapping mechanisms is essential for developing predictive models of oxygen transfer in bottled wine.