Effects of protein concentration, pH, and NaCl concentration on the physicochemical, interfacial, and emulsifying properties of β-conglycinin

The physicochemical characteristics, interfacial, and emulsifying properties of β-conglycinin (7S) at various protein concentrations (c), pH values (pH), and NaCl concentrations (NaCl) were characterized. The increase in c did not change the z-average diameters, solubility, and hydrophobicity but remarkably increased the net charges of 7S. The interfacial properties and emulsifying efficiency of 7S exhibited a dramatic dependence on the increase in c. Thus, the increased electrostatic repulsions facilitating the structural rearrangement and enough protein adsorbing onto the oil droplets' interfaces were the requirements for good emulsifying efficiency. 7S at pH 3 and 8 exhibited smaller z-average diameters, higher net charges, and solubility than that at pH 5, positively affecting their adsorption and the formation of viscoelastic layers. Thus, 7S at pH 3 and 8 showed better emulsifying efficiency. The increased NaCl did not change the z-average diameters, solubility, and hydrophobicity but decreased Zeta potentials of 7S due to electrostatic screening effects. Also, the increased NaCl improved interfacial adsorption kinetics but less viscoelastic interfacial layers of 7S. It suggested that low net charges decreased the electrostatic barrier for adsorption but did not benefit the intermolecular interaction of 7S at the interface. The emulsions aggregation at a high ionic strength indicated a negative effect on emulsifying activity.