A COMPARISON OF THE FUNCTIONAL AND INTERFACIAL PROPERTIES OF BETA-CASEIN AND DEPHOSPHORYLATED BETA-CASEIN

The functional and interfacial properties of beta-casein and dephospho rylated beta-casein (DeP beta-casein) were studied at pH 7.0 in 10 mM phosphate buffer. A decrease in emulsion stability and an increase in foamability was observed. Results from a variety of interfacial techni ques including electrophoretic mobility, thin film thickness, surface and interfacial tension, surface rheology, adsorbed layer thickness, a nd adsorption isotherms of dephosphorylated beta-casein and beta-casei n are reported. The results demonstrate that the phosphorylated groups of the N-terminal region of beta-casein are important for stabilizing emulsions. This is either as a direct result of charge repulsion betw een beta-casein N-terminal regions or more probably as an indirect res ult of the reduced N-terminal charge permitting DeP beta-casein to ado pt a different interfacial conformation resulting in a loss or reducti on of a steric barrier. (C) 1997 Academic Press.