Effects of pH and NaCl on the physicochemical and interfacial properties of egg white/yolk

The effects of pH and NaCl on the physicochemical (zeta potential, particle size and surface tension) and interfacial properties (foaming and emulsifying properties) of egg white and yolk were investigated in order to protmote its applications in food industries. Results showed that the increase of foam expansion power/emulsifying activity index of egg white exhibited a good correlation with the decrease of particle size and increase of surface tension. However, the extra charge and decreasing surface tension of egg white/yolk dispersions at pH > 7.0/ NaCl >= 0.6% resulted in the destabilization of foams. The emulsifying stability of egg yolk dispersions continued climbing to pH 10.0 due to the continuous reduction of particle size and started declining with the slow decrease amplitude of particle size at NaCl > 1.8%, thus z-average particle size is the main factor that dominates the emulsifying stability index of egg yolk dispersions. These results indicated that the foaming/emulsifying properties of egg white/yolk proteins can be manipulated by altering the physicochemical characteristics such as charge, surface tension and particle size in order to achieve optimal functional properties for food industrial applications.