The physical characteristics and emulsification properties of partially dephosphorylated bovine β-casein

Bovine β-casein was purified from phosphocasein by rennet coagulation and cold solubilisation from the resultant curd. β-Casein was then dephosphorylated using potato acid phosphatase. Urea-polyacrylamide gel electrophoresis (PAGE) of partially dephosphorylated β-casein showed a number of bands, depending on the final level of phosphorylation. Dephosphorylating β-casein increased its pH of minimum solubility from ∼pH 5 to 5.5 and reduced its net negative charge from -30.8 to -27.0 mV. During the acidification of β-casein solutions, partially dephosphorylated β-casein failed to form a gel, unlike the phosphorylated (i.e., control) β-casein. Use of partially dephosphorylated β-casein to stabilise oil-in-water emulsions resulted in larger fat globules compared to control β-casein, but such globules were less susceptible to aggregation in the presence of 15 or 30 mM CaCl(2). Overall, the dephosphorylation of β-casein resulted in a protein similar to human β-casein in terms of physicochemical functionality, with increased stability against calcium-induced aggregation.