A Comparison of the Functional and Interfacial Properties of β-Casein and Dephosphorylated β-Casein

Abstract

The functional and interfacial properties of β-casein and dephosphorylated β-casein (DeP β-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 techniques including electrophoretic mobility, thin film thickness, surface and interfacial tension, surface rheology, adsorbed layer thickness, and adsorption isotherms of dephosphorylated β-casein and β-casein are reported. The results demonstrate that the phosphorylated groups of the N-terminal region of β-casein are important for stabilizing emulsions. This is either as a direct result of charge repulsion between β-casein N-terminal regions or more probably as an indirect result of the reduced N-terminal charge permitting DeP β-casein to adopt a different interfacial conformation resulting in a loss or reduction of a steric barrier.