Mechanistic modulation of macromolecular interactions between modified cellulose and myofibrillar protein under low...

The effects and mechanisms of methylcellulose (MC), carboxymethylcellulose (CMC), hydroxypropyl methylcellulose (HPMC), and microcrystalline cellulose (MCC) on myofibrillar protein (MP) gelation at 0.3 M NaCl were investigated. Results showed that all celluloses enhanced the hardness, springiness, and water-holding capacity of low salt MP gel in a dose-dependent manner. Specifically, MC and HPMC reached optimal performance at 0.9% concentration, whereas CMC and MCC reached their peak at 0.3% addition. In particular, 0.9% MC addition gave the low-salt MP gel its highest hardness (502.98 g), water-holding capacity (98.7%), and storage modulus (3388 Pa), surpassing the normal-salt control. MC increased MP surface hydrophobicity from 58.9 to 86.1, facilitated disulfide and non-disulfide covalent cross-linking of myosin heavy chain intensity, and formed the densest gel microstructure. HPMC most strongly promoted low salt MP disulfide bond formation and achieved a water-holding capacity of 96.8%. However, its thermally reversible network partly dissociated upon cooling, limiting the storage modulus to 1656 Pa. CMC addition increased the absolute zeta potential from 17.4 mV to 34-37 mV via its carboxymethyl groups, generating electrostatic repulsion that impeded MP aggregation and led to a weak gel with high immobilized water but low water-holding capacity (86.8%). MCC behaved as an inert filler, yielding only marginal improvements. In conclusion, low-salt MP gel with MC addition surpassed normal-salt levels through hydrophobicity-driven unfolding and network reinforcement, with HPMC addition reaching normal-salt levels by enhancing disulfide bond formation, while the benefits of CMC and MCC additions were limited by electrostatic repulsion and inert filling.