How chloride salt mixtures affect the final gel properties of low-sodium myofibrillar protein: Underlining the perspective of gelation process

This study aimed to investigate the performance differences of low-sodium myofibrillar protein (MP) gels substituted by different chloride salt mixtures from the perspective of gelation process. The results revealed that low-sodium MP substituted by KCl/CaCl₂ exhibited higher turbidity and particle size at 40 % substitution, and formed protein aggregates earlier at 53 °C. During the gelation process, KCl/CaCl₂ increased the extent of cross-linking as the substitution level increased from 10 % to 40 %, which was prone to forming final gels with poor palatability. Microstructural and binarization results visually indicated that an irregular reticular structure composed of partial clusters formed when the temperature heated over 53 °C, and the cross-linked cluster blocks further shrunk from 53 °C to 73 °C. Rheological amplitude sweeps revealed that KCl/CaCl₂-substitued MP displayed a faster fracture of the ductile structure, and this influenced the distribution of cluster blocks inside the network. The introduction of salt mixtures altered protein conformation, and more unordered structures were found in low-sodium MP containing CaCl₂, rather than MP containing MgCl₂. Additionally, Ca²⁺ ions increased the thermo-denatured temperature of MP, and extended the relaxation time of bound water at 53 °C, and Mg²⁺ ions slowed down the degree of liquid loss at 53 °C. As a result, the low-sodium MP containing CaCl₂ exhibited a lower expansion of protein structure accompanied by the involvement of less proteins in gel formation and more liquid loss in the final gel.