Tribology and rheology of potato protein and pectin mixtures and Maillard conjugates

This study aimed to compare the tribological and rheological properties of plant proteins versus their mixtures or conjugates with polysaccharides. We hypothesize that combining potato proteins (Po) with pectin (Pe) at various concentrations (0.5–5.0 wt%, ratios 1:1 and 1:2 w/w) will improve the lubrication performance of plant proteins by virtue of viscosity modification and boundary lubrication. Po showed shear thinning behavior with limited concentration-dependence in boundary and mixed lubricity. Pe on the other hand showed pronounced concentration-dependent flow and lubrication behavior delivering favorable boundary and viscous lubricity. Pe dominated the lubrication and high shear rate flow behavior in Po + Pe mixtures, governed mainly by the concentration of Pe and the hydrodynamic volume rather than the total concentration of the biopolymers. Maillard reaction (≤33% degree of conjugation) led to more negatively-charged protein-polysaccharide conjugates versus the sole biopolymers (p < 0.05). The conjugation decreased the second plateau shear viscosity of the Po + Pe mixtures and led to improvement in boundary and mixed lubricity when a reduced entrainment speed parameter was used. Findings from this study may inspire future studies combining plant proteins with polysaccharides to enhance their lubrication behavior and eventually improve the textural properties of plant-based foods.