Modelling the viscosity of depletion flocculated emulsions

The rheological behavior of protein stabilized oil-in-water (O/W) emulsions containing free protein (sodium caseinate) in solution has been studied. The emulsions are shear-thinning due to reversible, depletion-induced flocculation. The effects of both protein and salt (sodium chloride) concentrations on the flow behavior of the emulsions have been analyzed. For this purpose, the effective potential of interaction between particles was estimated from rheometric data, using an appropriate viscosity model. Oil droplets were assumed to behave as hard spheres and to flocculate in the secondary minimum of the interaction potential curve. The rheometric results correlated quite well with theoretical predictions involving the DLVO theory plus an attractive potential due to depletion.