Why TPO should be measured
Measuring dissolved oxygen for quality assurance doesnt give you the full story. Typical TPOs, measured by AWRI Commercial Services bottling line benchmarking service across Australian and New Zealand facilities, have shown that typically over 60% of the oxygen in the bottle is in the headspace. If you are only monitoring the DO, then you are overlooking the majority of the oxygen that is getting into your wines at bottling.
All of the TPO ends up reacting with your wine, initially the oxygen dissolved in the wine matrix, then the oxygen from the headspace which must first dissolve into the wine matrix and then react with the wine constituents. The TPO value at bottling has been shown to have a significant impact on the shelf life of the wine post-bottling and it can also have an impact on the wine sensory properties. An example of the impact of best practice and worst practice TPO management at bottling on wine shelf life is shown in Figure 1.
Figure 1. Impact of TPO on wine shelf life – oxidised characters typically develop in white wines when the free SO2 values drop to approximately 10 mg/L
The wine bottled with an initial free SO2 level of 27 mg/L and industry worst practice oxygen management at bottling, a TPO of 5 mg/L, appears to be approaching its shelf life after only four months in the bottle!
How to measure TPO
Total package oxygen at bottling can be measured in a number of ways including the following:
- Oxyluminesence technologies – AWRI Commercial Services uses this as the reference method for conducting TPO benchmarking studies
- Technologies to measure dissolved oxygen (such as the Orbisphere) along with appropriate bottle shaking protocols and calculations to account for the residual oxygen in the headspace. This is explained further below.
Oxygen does not completely dissolve in wine – even after vigourous shaking a significant residual amount remains in the headspace. Measuring TPO at bottling is critical; however, many wineries only have equipment that enables them to measure the dissolved oxygen phase. To assist these wineries to effectively manage their bottling operations using their existing equipment AWRI Commercial Services has developed a method to approximate the TPO using a TPO calculator (Access the TPO calculator fact sheet).
This new method involves thoroughly shaking the bottle to establish an oxygen equilibrium between the wine and the headspace. Once equilibrated, the headspace retains some oxygen, as not all of the oxygen can dissolve in the liquid. The DO is measured using a standard Orbisphere or similar technology and entered into the online calculator (access the Total Package Oxygen calculator), along with the following:
- fill height
- bottle volume
- wine colour
With these inputs, an approximate TPO value is provided through a correlation developed using the oxyluminescience reference method.
TPO calculator setup
Please contact Commercial Services on firstname.lastname@example.org to arrange access.