Disclosed is a method for improving flavor quality and reducing water absorption of protein isolates, particularly soy protein concentrates. The method involves a surface treatment of the protein isolates with an aqueous solution containing a polysaccharide, in order to coat the protein isolates and block off the flavor of the protein molecule as well as serving as a moisture barrier. The treated protein isolates are then dried to a powder form. The resulting protein isolates are bland in taste, have a reduced water adsorption ratio as compared to the untreated protein isolate and can be used in a wide range of food products without flavor reversion.