Synergistic effects of κ/ι-Carrageenan and partial substitution of NaCl with MgCl2 or CaCl2 on the gel properties of myofibrillar protein

This study investigated the substitution of NaCl with MgCl 2 or CaCl 2 in κ/ι-car myofibrillar protein complexes (K/I-MP) to improve low-sodium gel meat products. Texture and cooking loss analysis showed that the effects of MgCl 2 or CaCl 2 depended on the carrageenan type and conditions. κ-carrageenan (κ-car ) exhibited a negative effect under Ca 2+ (cooking loss increased by 30.69%) and a positive effect under Mg 2+ (cooking loss decreased by 13.41%); both carrageenans showed regulatory effects, with κ-car having a greater impact. Analysis of hydrophobicity, sulfhydryl content, particle size, AFM, CD, rheology, infrared spectroscopy, and molecular docking revealed that Ca 2+ and ι-carrageenan (ι-car) formed complexes via salt bridges, significantly enhancing MP aggregation and structural stability. Infrared spectroscopy and molecular docking further confirmed that ι-car reacted more readily with MP than κ-car Particle size increased from 1.5 μm to 2.5 μm, α-helix content rose from 25% to 35%, and hydrophobic group exposure decreased. In contrast, κ-car promoted aggregation through hydrophobic interactions and sulfhydryl crosslinking, with a weaker increase in α-helix content (25% to 28%). Mg 2+ had a weaker effect but significantly enhanced aggregation when combined with κ-car. In conclusion, Ca 2+ enhanced MP structure via salt bridges, especially with ι-car, while κ-car promoted aggregation by altering protein conformation. Mg 2+ had a weaker effect but enhanced aggregation with κ-car. These findings provide new insights into the synergy between divalent cations and carrageenan in MP gelation and strategies for developing low-sodium meat products.