Rheology and stability of whey protein stabilized emulsions with high CaCl 2 concentrations

Abstract

The influence of pH and CaC1 2 on the rheology and physical stability of emulsions stabilized by whey protein isolate (WPI) has been studied. The particle size, creaming index and shear viscosity of 10 wt% soy bean oil-in-water emulsions (d=0.55 μm) were measured with varying pH (3, 5 and 7) and CaC1 2 concentration (0–150 mM). In the absence of CaCl 2 extensive droplet aggregation occurred around the isoelectic point of the whey proteins (4<pH<6) because of their low electrical charge. In the presence of CaC1 2, extensive droplet aggregation, viscosity enhancement and creaming instability occurred at pH 7 for CaC1 2>3 mM. These effects were much less pronounced in emulsions at pH 3 even at 150 mM CaC1 2. Droplet aggregation, creaming and viscosity of emulsions at pH 5 were fairly independent of CaC1 2 concentration. Droplet aggregation was induced by CaC1 2 probably because of the reduction in electrostatic repulsion between droplets. Re-stabilization of oil-in-water emulsions at high CaC1 2 concentrations was not observed in this study.