phorylated, according to the specifications of the supplier The functional and interfacial properties of b-casein and de- (Sigma Chemical Co.). This results in the net negative phosphorylated b-casein (DeP b-casein) were studied at pH 7.0 charge of the N-terminal 50 amino acids, at pH 7.0, decreasin 10 mM phosphate buffer. A decrease in emulsion stability and ing from approximately 011 to 03. This decrease in net an increase in foamability was observed. Results from a variety of negative charge is not accompanied by a decrease in solubilinterfacial techniques including electrophoretic mobility, thin film ity (5). However a decrease in emulsion and foam stability thickness, surface and interfacial tension, surface rheology, adhas been reported as a result of dephosphorylating total casorbed layer thickness, and adsorption isotherms of dephosphorysein ( 5) but the underlying mechanisms remain unclear. lated b-casein and b-casein are reported. The results demonstrate In this paper we report results of an investigation of the that the phosphorylated groups of the N-terminal region of bcasein are important for stabilizing emulsions. This is either as a foaming and emulsification properties of b-casein and 80% direct result of charge repulsion between b-casein N-terminal redephosphorylated b-casein. The properties of the adsorbed gions or more probably as an indirect result of the reduced Ninterfacial layer are important in determining functional beterminal charge permitting DeP b-casein to adopt a different inhavior. Previous studies on emulsion stability of proteins terfacial conformation resulting in a loss or reduction of a steric (8) showed that b-casein formed emulsions which were barrier.