Mechanistic modulation of macromolecular interactions between modified cellulose and myofibrillar protein under low salt conditions: effects on gel properties.

Abstract

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.