Linear and nonlinear rheological characterization of capillary protein oleogels as potential fat replacers: Comparison with high internal-phase emulsions

The rheological behavior of fats or fat replacers is shaped by the interaction among colloidal assemblies giving rise to a specific structural network. We hypothesize that the capillary protein oleogels formation we proposed, in which colloidal protein particles are used as initial building blocks to form space-spanning networks, has linear and nonlinear rheological behaviors similar to fat crystal networks as represented in fractal rheo-mechanical models. Capillary protein oleogels and repulsive high internal-phase emulsions (HIPEs) differing in microstructure categories were therefore assembled for a systematic comparison, as both serve as motivating exemplars for fat replacement. Confocal laser scanning microscopy (CLSM) were employed to distinguish the structural characteristics. By employing both small- (SAOS) and large-amplitude oscillatory shear (LAOS) rheology via Chebyshev polynomial analysis, we examined the linear and nonlinear responses of capillary oleogels and HIPEs under relevant deformations. Differing from the caging effects of droplets within HIPEs, the hierarchical networks with attractive protein particles of capillary oleogels are responsible for interpreting the rheological characteristic parameters in SAOS rheology, and for enhancing resistance to deformation in LAOS due to the coexistence of interparticle interactions and cluster characteristics. The capillary oleogels with attractive protein particles show a similar behavior to that of the fat self-assembled fractal flocs or aggregates in the fractal rheo-mechanical models. These results give us hope that by tailoring the nano- and mesoscale structural organization within a fat replacer in a specific way, there is potential for achieving proper functionality in food products, such as plastic flow behavior.