Flocculation of Whey Protein Stabilized Emulsions as Influenced by Dextran Sulfate and Electrolyte

The creaming stability and viscosity of oil-in-water emulsions stabilized by whey protein isolate were monitored as functions of dextran sulfate (DS) and electrolyte (NaCl) concentration. At a specific DS concentration (the critical flocculation concentration, CFC), the droplets became flocculated, which promoted creaming. Addition of electrolyte caused an increase in CFC. At NaCl concentrations <0.5 wt%, addition of electrolyte decreased emulsion viscosity, but at concentrations >0.5 wt% it caused an increase in viscosity due to increased flocculation. The results were due to the influence of electrostatic screening on the effective volume of DS molecules and colloidal interactions between droplets.