No acidification is needed for the soups because of the long process time in the PC.

Using the example of tomato sauce, by adding an acid to the sauce the PC time can be shortened. The shorter processing time results in a better quality product. However, the processing the sauce gets in the PC is only equivalent to that of a boiling water bath. Without the acid the PC time would be much longer. Hope that makes sense...

Rodney

Agree with Rodney. Plus the density is quite different from that of tomato sauce. Acidification is only ONE aspect of canning safety. Time under pressure and density of the food are equally important.

Dave

Thank you Rodney and Dave!