Phosphorylation modification of collagen peptides from fish bone enhances their calcium-chelating and antioxidant activity

In order to investigate the impact of phosphorylation modification on fish bone collagen peptide (CP), CP was subjected to phosphorylation modification to generate phosphorylated collagen peptide (P-CP). CP and P-CP were further chelated with calcium to form calcium-chelated collagen peptide (Ca-CP) and calcium-chelated phosphorylated collagen peptide (Ca-P-CP). The structural changes before and after phosphorylation and chelation reaction were characterized. Additionally, their stability and antioxidant activity were evaluated. The calcium-binding capacity of CP was significantly enhanced by phosphorylation, and the highest calcium-chelating capacity reached 128.21 mg/g. The introduction of phosphate ions caused esterification reaction, while the carboxyl groups, amino groups and phosphate groups of CP and P-CP were responsible for binding to calcium ions. Ca-P-CP exhibited an excellent stability (calcium retention rates >80%) towards a wide range of temperatures, pH as well as gastrointestinal digestion. Furthermore, DPPH and superoxide anion radical scavenging activities of CP and P-CP were significantly increased after chelation with calcium ions. Overall, phosphorylation modification can effectively improve the calcium-chelating ability of CP, while the resultant chelates possessed high antioxidant activity and stability. The chelates in the present study are promising to be applied as calcium supplements with high efficiency, bioactivity and stability.