Comparison of oral tribological performance of proteinaceous microgel systems with protein-polysaccharide combinations

Polysaccharides are often used as rheology modifiers in multiphasic protein-rich food systems. Recently, proteinaceous microgels have garnered research attention as promising lubricating agents. However, whether proteinaceous microgels can be used to replace polysaccharides in a tribological context remains poorly understood. In this study we compared the flow and oral-tribological behaviour of Newtonian solutions of the polysaccharide dextran (D, 1-11 wt%) when combined with a dispersion of whey protein isolate (W, 1-13 wt%) or whey protein microgel (WPM, 41.7 vol%) and compared with microgels of D-conjugated to W (Conj(D[11] + W[5])MG) or dispersions of WPM in W solutions. W and WPM alleviated frictional forces between elastomeric surfaces as well as biomimetic tongue-like surfaces in the boundary lubrication regime. Despite the negligible influence of D on the thin-film lubricity, its impact on viscous-facilitated lubricity was significant. The importance of measurements with the tongue-mimicked setup emerged where Conj(D[11] + W[5])MG did not show significant lubricity enhancement despite its outstanding performance with conventional tribo-testing setups. By optimising a combination of WPM and non-microgelled W, we demonstrate that a combined viscous and thin-film lubricity could be achieved through a single-protein-component without the need of polysaccharides. The dispersions of WPM (41.7 vol%) deliver the same flow and viscous-friction behaviour to that of 5 wt% D and excel in thin-film lubricity. These findings pave the way towards design of processed foods with clean labels, taking advantage of using a single proteinaceous moiety whilst delivering enhanced lubricity and viscosity modification without the need of any additional thickener.