Your absolutely right I should have put my references in my reply. From the top of my head it was an paper that led me to believe that oxygen was only in part responsible for the degradation of actives so if that’s true then there must be another mechanism that can cause the effect, enzymes would be suspect.

I’m now almost without internet access and it wil take a month before I can properly reply back, so i have to leave the answer vague for now.

Interesting to see the results from the graph, I would say that the data suggests that there is a minimal difference and I wonder if this would be significant for a larger sample size. Now I would say that there not significantly different and that this actually supports the idea that there is more to is than just oxygen.