Rheological properties of oil-in-water emulsions formed with milk protein concentrate

The rheology and the microstructure of emulsions stabilized with milk protein concentrate (MPC) were investigated using different MPC and oil concentrations. Steady-shear tests showed that the emulsions were Newtonian at low oil concentrations (< 20 wt%), whereas they were pseudoplastic and thixotropic at high oil concentrations (> 20 wt%). Dynamic rheological measurements demonstrated that these emulsions behaved as weak gels, as indicated by relatively high values of G' to G'. The rheological behavior of these emulsions was consistent with bridging flocculation mechanisms, whereby more than one droplet is shared by adsorbed casein aggregates/micelles. This was confirmed by confocal microscopy, which showed that these emulsions were aggregated.