Yuxia Jin, Chaofan Guo, Yutong Liu, Xingwei Wang, Xianchao Feng, Jianxin Cao, Xuejiao Wang
This study investigated the effects of KCl substitution for NaCl on the structural properties, Na+ release, and saltiness retention of κ-carrageenan-myofibrillar protein composite gels under low ionic strength conditions. Composite gels were prepared at a total ionic strength of 0.1 mol/L with 0.5% κ-carrageenan, in which NaCl was replaced by KCl at levels of 0%, 20%, 50%, and 100%. The effects of KCl substitution on gel properties, microstructure, intermolecular interactions, Na+ release during oral processing, and sensory characteristics were evaluated. Moderate KCl substitution significantly improved gel properties, with the 20% KCl group exhibiting the highest gel strength, viscoelasticity, and water-holding capacity. Microstructural analysis revealed that 20% KCl substitution promoted the formation of a continuous and compact protein-polysaccharide network, whereas excessive KCl substitution caused heterogeneous aggregation and structural defects. The enhanced gel properties were associated with increased hydrophobic interactions and disulfide bonding, which stabilized the network and improved water immobilization. During oral processing, the 20% KCl group maintained efficient Na+ release, achieving comparable late-stage Na+ release to the full NaCl group, and showed the highest saltiness perception and overall acceptability. Moderate K+ incorporation promoted κ-carrageenan network formation while retaining sufficient Na+ to support myofibrillar protein gelation. The reconstructed protein-polysaccharide network facilitated Na+ migration and release during chewing, thereby compensating for saltiness loss caused by sodium reduction. Overall, 20% KCl substitution (0.08 mol/L NaCl +0.02 mol/L KCl) achieved a balance between sodium reduction, structural enhancement, and saltiness retention, providing a potential strategy for developing low-sodium meat products.