Hierarchy-dependent mechanical reinforcement in gelatin-whey protein composite hydrogels and high internal phase...

Protein composite hydrogels (PCHs) and high internal phase emulsion gels (HIPEs) are widely used as fat mimetics, yet their reinforcement mechanisms across hierarchical structures remain unclear. Here, gelatin (GEL)-whey protein isolate (WPI) composites were used to systematically compare the effects of thermal treatment, enzymatic cross-linking, and Hofmeister salting-out on PCHs and corresponding HIPEs. Identical compositions and treatments produced distinct structure-mechanics coupling in the two systems. In PCHs, mechanical performance was governed by the continuous GEL network, with WPI acting as a dispersed, particle-like modifier. In contrast, emulsification redistributed proteins between the continuous phase and oil-water interface in HIPEs, forming load-bearing continuous phase networks. Our findings demonstrate that the strengthening behavior of GEL and WPI follows quasi-orthogonal responsibility, attributable to their intrinsic structural differences. This mechanistic insight provides a rational basis for structuring cultured fat scaffolds and fat analogues with tough mechanical properties suitable for practical applications.