Adsorption and reorganisation of whey proteins onto a molten milk fat droplet interface through experimental and modelling assessment

Milk is a complex emulsion, and understanding the adsorption of the various surface-active macromolecules onto the fat/water interface newly formed during homogenization is critical for optimizing dairy processing. This study investigates the adsorption dynamics using a commercial whey protein ingredient and melted anhydrous milk fat (50 °C). By employing drop surface tension measurements, interfacial dilatational rheology and a comprehensive modelling approach, we explore the adsorption process under realistic conditions. We propose a model describing diffusion, progressive saturation of the surface and reorganisation of proteins. For reorganisation, the proposed model introduces three parameters: the maximum loads of the interface without (Γ_min) and with (Γ_max) reorganisation and a characteristic time of reorganisation (τ_reorg). The kinetic properties of whey proteins have been characterised by adjusting the parameters of the model. In addition, interfacial rheology and macroscopic observations of the droplets revealed regime changes in the organisation of the interface, confirming our hypothesis about the reorganisation built into the model. This study opens the way to the construction of a model for predicting the composition of the interface after homogenization at high pressure (HPH), taking account of competition between macromolecules (casein, phospholipids etc.).