Measuring oxygen ingress into bottles
Background
Oxygen plays an important role in wine development. Work carried out at The Australian Wine Research Institute and elsewhere has shown that a single wine bottled with a different closure or headspace develops into different wines. These different wines age in different ways. A large part of this differentiation is due to the closures: different closures allow different amounts of oxygen into the wine bottle. Being able to quantify how much oxygen can pass through a closure is therefore an important tool for the winemaker and packager.
Progress
We have developed a method which allows the calculation of not only the oxygen ingress rate through closures, but also the initial amount of oxygen in the headspace of a wine bottle and the amount of oxygen entrapped in the closure. This new assay uses methylene blue and light to convert dissolved oxygen into singlet oxygen, the reactive form of oxygen, and a water-soluble compound [(BPAA); bis-9,10-anthracene-(4-trimethylphenylammonium)-dichloride] to trap singlet oxygen. The reaction product formed when BPAA reacts with singlet oxygen has a different absorption spectrum than BPAA. The change in absorbance after the reaction can then be related to the quantity of oxygen present. By using a modified spectrophotometer, these reactions can be undertaken in synthetic wine solutions and measured in a wine bottle sealed with closures inserted under normal commercial conditions. The determination of oxygen permeation rates is calculated from measurements made over an eight week period under controlled storage conditions.
We are now in a position to use the non-destructive BPAA method to more rapidly evaluate the route of oxygen ingress into bottled wines and validate the data we have already obtained. This information will add to a growing body of knowledge that we plan to collect during the next few years in order to assess the relative importance of winemaking practices, packaging choices and transport and storage conditions on wine development and oxidative spoilage. Our ultimate aim is to be able to develop models to allow predictions of shelf life to be made at various stages of a bottled wine’s ‘life’.
Highlights
Method developed that measures:
- Oxygen ingress into wine bottle
- Oxygen trapped within closure
- Oxygen within the headspace.
Images:
Figure 1. The ingress of oxygen into a 375 mL volume wine bottle sealed with a synthetic closure during storage at 80°C. Oxygen content was determined, non destructively, from the loss of BPAA (Source: AWRI Annual Report 2008, p. 20)
Project leader: Dr Liz Waters
Project team members:
Publications:
528 Waters, E.J.; Peng, Z.; Pocock, K.F.; Williams, P.J. The role of corks in oxidative spoilage of white wines. Aust. J. Grape Wine Res. 2: 191-197; 1996 (click here to order).
534 Caloghiris, M.; Waters, E.J.; Williams, P.J. An industry trial provides further evidence for the role of corks in oxidative spoilage of bottled wines. Aust. J. Grape Wine Res. 3: 9–17; 1997 (click here to order).
1069 Skouroumounis, G.; Waters, E. Oxygen ingress into bottled wine. Pract. Winery Vineyard July/August: 6-14; 2008 (click here to order).