Influence of particle size and interfacial interactions on the physical and mechanical properties of particle-filled myofibrillar protein gels

Abstract

The physical and mechanical properties of particle-filled composite gels are influenced by a variety of factors which are often system-specific. Here, we report on the effect of solid fillers of varying sizes and surface properties in a model gel system; heat-set comminuted meat protein gels. Hydrophobic rice bran wax particles and hydrophilic glass beads were selected for their contrasting surface chemistry, which influenced the particle/gel interfacial interactions. All the composites were found to be stable up to 0.5 volume fraction filler, based on post-gelation liquid loss, light microscopy, and cryo-SEM analyses. The influence of the dispersed particles on the large deformation mechanical properties of the composites were evaluated based on particle type, size, and volume fraction of the filler. The behavior of the Young's modulus was compared to that predicted by particle reinforcement theories proposed by van der Poel and Kerner, each with subsequent extensions. Both filler type and size were found to influence the Young's modulus and stress at 50% strain. The recoverable energy and post-compression height recovery were found to be predominantly influenced by the filler volume fraction, and were less influenced by particle/gel interactions. Interestingly, filler type and size range were found to have no effect on the cohesiveness of the composites, as this parameter was found to be solely dependent on the volume fraction of the extensible continuous phase. The influence of the filler on the optical properties of the composites was evaluated by reflectance spectroscopy in the visible range, and interpreted based on the effect of the filler optical properties. The results from this study indicate that filler size, surface chemistry, and incorporation level can strongly influence the macroscopic physical characteristics of heat-induced comminuted myofibrillar protein composite gel systems.