Influence of pH and CaCl2 on the stability of dilute whey protein stabilized emulsions

The influence of pH and CaCl2 on the physical stability of dilute oil-in-wa ter emulsions stabilized by whey protein isolate has been studied. The part icle size, zeta potential and creaming stability of 0.05 wt% soy bean oil-i n-water emulsions (d approximate to 0.53 mu m) were measured with varying p H (3 to 7) and CaCl2 concentration (0 to 20 mu M). In the absence of CaCl2 extensive droplet aggregation occurred around the isoelectric point of the whey proteins (4 < pH < 6) because of their low electrical charge, which le d to creaming instability. Droplet aggregation occurred at higher pH when C aCl2 was added to the emulsions. The minimum concentration of CaCl2 require d to promote aggregation increased as the pH increased. Aggregation was ind uced in the presence of CaCl2 probably because of the reduction in electros tatic repulsion between droplets, caused by binding of counter ions to drop let surfaces and electrostatic screening effects. (C) 2000 Elsevier Science Ltd. All rights reserved.