Steady, dynamic, and creep-recovery rheological properties of myofibrillar protein from grass carp muscle

Abstract

This study investigated the solution behaviors and sol–gel transition of myofibrillar protein (MP) from grass carp muscle by rheological methods. In steady shear measurements, shear-thinning behavior was observed in the MP solutions and became more apparent with increasing concentration (c), though Newtonian plateaus appeared at c ≤ 0.025 mg/mL. Based on the Cross model, zero shear viscosity (η0) and structural relaxation time (K) increased with increasing c, indicating the reinforcement of chain interaction and entanglement. From the dependence of η0 on c, the MP showed the rod-like polymer features due to its α-helical tail, and the coil overlap concentration (c*) was estimated to be 4.5 mg/mL, at which the MP coils begin to overlap and interpenetrate undergoing the transition from a dilute to concentrated solution. In frequency sweep, the MP system was classified to two regions: an entanglement network or concentrated solution (5 and 10 mg/mL), and a weak gel (15 and 20 mg/mL). Furthermore, the sol–gel transition concentration (cgel) was further identified as 13 mg/mL by the Winter–Chambon criterion. According to the creep-recovery data fitted by the Burger model, the elastic coefficients (G1 and G2) and viscous coefficients (η1 and η2) increased with increasing temperature (5–40 °C), while the maximum deformation (JMAX) and residual deformation (J∞) decreased, leading to an increase in the final percentage recovery (R%). This result indicated that the chain rigidity of MP increased with elevated temperature, the MP gel network formed and became stronger, confirming the denaturation, aggregation and pre-gelation of MP at ∼40 °C.