The aim of the present study was to investigate the effect of the protein heat treatment on the physical properties of whey protein concentrate dispersions and the resulting protein-stabilized 30% O/W emulsions. Protein preheating influenced protein particles sizes, viscosity, density, emulsifying capacity and conductivity of protein dispersions. Emulsion stability was improved by protein heat treatment. The emulsions showed bimodal particle size distributions and higher particle sizes with increasing temperature. Thermal modification of the continuous phase influenced flow characteristics of the emulsions and did not affect emulsion conductivity. Heating of whey proteins may generate stable nano-particles and/or aggregates that are able to improve stability of the emulsions. These small structures may stabilize the emulsions by increasing viscosity of the continuous phase and by taking part in formation of the second protein layer on the oil droplets. (C) 2010 Elsevier Ltd. All rights reserved.