Experiment on protein characterization, neutralization and hydrolysis?

We did an experiment on protein characterization, neutralization and hydrolysis, why do we need to use barium hydroxide (for acid hydrolyzate) and H2SO4 (alkaline hydrolyzate) to neutralize it? And why after autoclaving and hydrolyzing the isolated intact protein (casein) from skim milk it became black for acid and creamy for base? Would really appreciate your help… Thanks!