Highly effective peptide-calcium chelate prepared from aquatic products processing wastes: Stickwater and oyster shells

Stickwater and oyster shells can be used as cost-effective sources to produce high-value peptide-calcium chelate. In this study, the optimal preparation process of chelate from peptides of stickwater hydrolysate and calcium of oyster shells was determined by response surface methodology, under which a high calcium chelation rate of 87.62% was achieved. The analysis of peptides sequence showed that all chelated peptides were from the myosin light chain, and the molecular weight of most of them was lower than 1500 Da. There were 19, 20, and 19 of the 26 chelated peptides containing Glu, Asp, and Gly residues, respectively, which have been proved to exhibit high calcium-binding ability in previous studies. Structural characterizations revealed that –NH2, COO-, N–H, CO, C–H, and –OH groups might participate in the formation of peptide-calcium chelate, and new interaction forces of crystal structure were generated in the chelate. Besides, morphology analysis showed that folded, aggregated, and compact structures formed in the peptide-calcium chelate. Moreover, the peptide-calcium chelate was relatively stable under high temperature and digestion conditions in the gastrointestinal tract, indicating that it could be used as a highly effective calcium supplement.