Effect of Ca2+ on the structure of collagen fibers in sea cucumber (Apostichopus japonicus) under low-temperature tenderization condition

Collagen fibers (CFs) are essential in maintaining the structural integrity of sea cucumber body wall tissues. Addition of Ca²⁺ to meat products improves tenderness and modulates the levels of chemical interactions in CFs. In this study, we investigated the effects of Ca²⁺ (ranging from 0 to 40 mM) on the structural organization and thermal stability of CFs. The dissolution of protein and polysaccharide of sea cucumber collagen fiber was less under low concentration of Ca²⁺ (2.5 mM-10 mM), and the dissolution amount corresponding to high concentration of Ca²⁺ (20 mM, 40 mM) increased. FTIR, XRD, DSC, TGA and SEM analyses revealed that low concentrations of Ca²⁺ (2.5 and 5 mM) increased the intermolecular binding of CFs, enhanced stability of triple helix structure, maintained the structural integrity of CFs, and inhibited the degradation of CFs. This study provides insights into enhancing the quality of sea cucumber through low-temperature tenderization.