The functionality of caseins in food systems depends on their solubility. The solubilities of whole casein, cr,l-casein, /3-casein, and dephosphorylated whole casein were measured as the pH was adjusted from 7 to 2 with HCl. When NaCl was added before pH adjustment, solubilities of whole casein at pH 2.5 decreased by 25, 40, 85, and 98% at NaCl concentrations of .01, .05, .1 and .2 M, respectiv...