Preparation of Calcium-Chelating Peptides from Squid Skin and Evaluation of Calcium Absorption Capacity in Caco-2 Cell Monolayer Model.

To develop a highly bioavailable calcium supplement, this study utilized Peruvian squid (Dosidicus gigas) skin as a raw material. Through alkaline protease hydrolysis and enzymatic membrane reactor separation, three molecular weight fractions of squid skin peptides were obtained, followed by calcium ion chelation to synthesize calcium-chelating peptides (CCPs-SS). Systematic characterization revealed that the less than 1 kDa fraction of CCPs-SS exhibited superior antioxidant capacity (82.18%) and calcium chelation efficiency (77.14%) in cellular models compared to higher molecular weight counterparts. Optimal synthesis conditions were identified as 60 °C, pH 9, and 12 mg/mL calcium chloride concentration. Post-chelation analyses demonstrated significant physicochemical alterations for CCPs-SS: ζ-potential shifted from -18.4 mV to -10.47 mV, while particle size increased from 476.75 nm to 664.4 nm. Notably, membrane separation enhanced phenylalanine and leucine molar concentrations by 25.5% and 57.6%, respectively, suggesting structural modifications that potentiate bioactivity. These findings demonstrate an innovative strategy for converting squid processing byproducts into functional nutraceuticals, which not only addresses calcium deficiency challenges but also promotes resource sustainability by utilizing waste materials.