Figure II: Oxygen in wine at different stages of bottling process. [Friedel, 2007]

Physical laws, wine chemical compounds, in addition to different solubilities, densities, and diffusions between the gases in the headspace and liquid phase are essential parameters that will influence the oxygen content of the bottled wine. The key decision for the winemakerwill bewhether to give thewine a longer or shorter “potential lifespan.”

Oxygen uptake can also be influenced depending on the filler-system and design of the filling valves or use of air evacuation in the bottle before filling. This has been proven and the effects can be observed in the wine shortly after bottling.

Figures II and III showthe impact of the oxygen content in wine determined by the stage of bottling process (Figure II) and the use of different filling systems (Figure III).

Generally, filling procedures describe the way and methods that are used to bring a sterile product into the bottle. This can be done by filtration of thewine or also by a pasteurization or warming of the alcoholic beverage. Common filling procedures are: cold aseptic with filtration or flash pasteurization before bottling, warm aseptic with or without recooling, or cold with pasteurization after bottling. Use of the three different techniques will influence the solubility of oxygen in the wine because of the different temperature occurring but also the enzymatical system which enables or disables oxidation also.

Figure III: Oxygen in wine using different filling systems. [Mc Lellan, 1990]

The first storage period is the time that is needed for the wine to consume all the oxygen coming from the headspace. This length of time is determined by the content of oxygen in the headspace, the pressure, temperature, and wine components. From past Geisenheim bottling experiments, our experience is that this can last from 10 days up to three to four months.

Using an inert gas in the headspace of the bottle between the fill-level of the wine and the closure greatly reduces the quantity of oxygen which can be dissolved in a wine.

Figures IV and V demonstrate the influence of CO2 and N2 headspace treatments on the oxygen content in wine.

In Figure IV and V, the reducing effect of a headspace treatment is very evident. It is interesting to note that by not flushing the headspace with an inert gas, the oxygen content in wine increases within days after bottling. This results from oxygen in the headspace being transferred continuously into the liquid by diffusion between the gaseous headspace and the wine.

The input of oxygen into wine prior, during, and after the bottling process is determined by physical constraints and chemical composition of a wine. It can be influenced by using different filling systems and procedures and, more significantly, by using inert gases to flush the headspace in the bottle and evacuating bottles prior to filling.

For the past 15 years, the Department of Enology and Wine Technology at the Geisenheim Research Center, has conducted various bottling trials in order to evaluate alternative bottle closures. Thanks to this research,we have been able to observe the effects on oxygen transfer into thewine described in this article.

For current projects dealing with the measurement of oxygen transfer before and during bottling,we use the non-invasive and non-destructive “PreSens” fiber optic oxygen measurement. Moreover, we are examining, after bottling, development of dissolved oxygen and sulphur dioxide inwines during storage andmaturation. The chemical and sensorial changes inwine aromas are also analyzed and correlated with different bottling options and storage conditions.