Increasing the heat stability of whey protein-rich emulsions by combining the functional role of WPM and caseins

Abstract

The heat stability of whey protein emulsions remains a real challenge due to the rapid denaturation/aggregation of native whey proteins on heating. The use of heat-stable Pickering-like whey protein microgels (WPM) makes it possible to develop heat-stable emulsions in a large range of whey protein concentrations. In this study, emulsion heat stability was evaluated with a special focus on the contribution of WPM adsorbed at the fat droplet surface and in the continuous phase of the emulsion. Dairy emulsions were prepared with 30% milk fat and 70% suspension of WPM in the dispersed phase of milk. The protein interfacial load and the composition of the fat droplet surface were determined immediately after emulsion formation, and the heat stability of the emulsions at 120 °C was assessed visually and at microscopic scale. WPM are heat stable in the continuous phase of the emulsion, but the presence of WPM at the surface of the fat droplets is responsible for a rapid gelation of the emulsions. In the heated emulsions, the fat droplets seemed to be crosslinked by WPM. The presence of caseins instead of WPM at the fat droplet surface allowed the heat stability of the emulsion to recover at low and high whey protein concentrations. This study shows that it is possible to prepare heat-stable whey protein–rich emulsions by using whey proteins previously aggregated as heat-stable WPM and a sufficient amount of caseins in order to fully cover the fat droplet surface. These results will contribute to the development of heat-stable whey protein–rich emulsions.