Lubrication behavior of mixed colloidal systems: Effect of interactions between polysaccharides and oil droplets/ protein particles

The lubrication behavior of food systems is critical for sensory perception and consumer acceptance. This behavior depends on the components present in food and their interactions. In the present study, binary systems were designed to systematically investigate the effect of the interactions (i.e. repulsive and attractive interactions) between components on lubrication properties. Whey protein-stabilized emulsion droplets or whey protein aggregates functioned as dispersed particles, while polysaccharides were present in the continuous phase. Polysaccharides with different molecular characteristics, i.e. xanthan (charged, stiff), pectin (charged, semi-flexible) and guar gum (non-charged, flexible), were selected. We observed that bridging due to attractive interactions between polysaccharides and particles (oil droplets or proteins aggregates) induced extensive particle aggregation, leading to increased friction coefficients. Such bridging was reduced as the concentration of polysaccharides increased, decreasing both cluster size and friction coefficient. In the case of systems with the same charge, weaker depletion interactions led to the formation of particle aggregates, resulting in increased friction coefficients. This was mostly observed for pectin. Conversely, addition of xanthan and guar gum did not cause extensive aggregation and a more homogeneous microstructure was observed. As a result, lower friction coefficients were obtained. The friction coefficients were reduced further when more xanthan or guar gum were added, the highly charged xanthan being more effective. Overall, for both types of interactions, systems with a more homogeneous microstructure (i.e. smaller clusters) resulted in lower friction, indicating that the microstructure of the systems was the primary determinant of lubrication behavior.