The assaying of oxygen in the headspace of a bottle combined with that of dissolved oxygen in the wine makes it possible to obtain the total oxygen per bottle. The first analyses performed at bottling show that 0.38 to 3.58 mg oxygen per bottle is trapped in the headspace. Operating conditions account for these substantial variations. Monitoring the oxygen contents in the liquid and gas phases of three batches of wine over a period of several months and the analysis of old bottles show that the headspace functions as an oxygen reserve for the wine, that is to say that as the wine uses oxygen, there is passage of the gas from the headspace to the wine. This is related to a movement towards a balance between the two phases as the partial pressure of oxygen in the gas phase is always greater than that of the liquid phase. Finally, this gas exchange kinetics within the bottle outweighs the kinetics of penetration of the bottle by oxygen in the external atmosphere, at least while the total oxygen trapped at bottling has not been used up.
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