The paper describes an application of immunoblot analysis of two different protein materials (pea and milk) hydrolysed with selected enzymes (Alcalase, pronase and papain). “One-step” hydrolysis of whey protein concentrate (WPC) resulted in hydrolysates characterized by insignificantly decreased immunoreactivity of both α-lactalbumin (α-la) and β-lactoglobulin (β-lg). “Two-step” hydrolysis of WPC in pronase-Alcalase system contributed to higher lowering of immunoreactive properties of WPC. When sodium caseinate was hydrolysed in both “one-step” and “two-step” system, the immunoreactivity of casein proteins (α-casein, β-casein and κ-casein) was lowered so that there were observed no reactions with polyclonal antibodies directed against α-, β-, and κ-casein on immunoblotting membranes. Hydrolysis of pea proteins with Alcalase resulted in significant lowering of vicillin immunoreactivity and much higher lowering of legumin immunoreactivity. It was found by immunoblotting method that there were no reactions between pea hydrolysed proteins and anti-legumin antibodies.