The inclusion of a fluorogenic protease substrate in a mock reaction is often a useful method to gauge proteolysis in complex mixtures. Thermo has several useful substrates:

https://www.thermofisher.com/us/en/home/references/molecular-probes-the-handbook/enzyme-substrates/detecting-peptidases-and-proteases.html

When the fluorescent signal asymptotes out you can infer that the original sample is digested. An important control is of course the fluorogenic protease substrate minus the complex mixture.