Mechanical properties of myofibrillar protein-cellulose nanofibril composite gels: Role of protein concentration and network structure

Abstract

While prior investigations have predominantly explored myofibrillar protein (MP) gel modification via pH regulation and polysaccharide complexation, the mechanistic influence of MP concentration gradients in composite gel architectures remains insufficiently characterized. This study systematically investigates the concentration-dependent behavior of MP-cellulose nanofiber (CNF) composite gels, elucidating the structural and mechanical interplay between the protein matrix density and polysaccharide reinforcement. Multiscale characterization revealed that an increase in MP concentration (20–200 mg/mL) led to progressive microstructural densification, which correlated with increased hardness (150%–1290%) and improved water holding capacity (17.6%–86%). This phenomenon may be attributed to the rise in the content of β-sheet and β-turn within the composite gels. Notably, the enhancing effect of CNF on the composite gel exhibits a critical concentration threshold only in the M-20 group. In contrast, in a high-concentration MP system, the effect of CNF is negligible due to protein intermolecular interactions and spatial repulsion. Similarly, rheological analysis showed that the enhancing effect of CNF on the composite gel was also influenced by the MP concentration. Finally, by integrating percolation theory with protein-polysaccharide interfacial parameters, the Ouali model successfully provided an accurate prediction of the mechanical properties of the composite gels. Overall, the theoretical framework developed in this work facilitates precise control over the mechanical properties of protein-polysaccharide composite gels and offers theoretical insights into the development of novel gel-based meat products. • Elevated MP concentration enhances the network strength and improves the hardness and WHC of the gel. • CNF percolation threshold emerges only in low-MP gels, suppressed at high MP by molecular crowding. • Ouali model predicts gel modulus accurately with steric hindrance/aspect ratio.