This is an old thread, but I found it helpful. I have been questioning whether it is really necessary to add Kmeta and then wait 12 hours to add pectic enzyme. If Kmeta is harmful to pectic enzyme there would be two possibilities:
1. The Kmeta would destroy the pectic enzyme
2. The Kmeta would inhibit the pectic enzyme, but not destroy it
In the case of #2 it would be no problem to add the enzyme at the same time as Kmeta, since once enough SO2 dissipated it would begin to work. In case #1, it would be important to wait before adding pectic enzyme, at least if the Kmeta levels were high enough to destroy it. According to the experiment done by Luc above, that might not be a problem.
I have not seen any solid evidence that #1 is the case, so I plan to return to my original method of adding pectic enzyme and Kmeta together at the beginning. Why make this more complicated than it needs to be?