Sustainable and one-pot fabrication of peptide chelated calcium from fish scale hydrolysates

Fish scales, considered as low-value by-products, contain peptides and hydroxyapatite that can be applied to produce peptide chelated calcium directly. This study developed a sustainable and one-pot fabrication method for the peptide-chelated calcium from fish scale hydrolysates (FSP-Ca). During pepsin hydrolysis, the releases of peptides (FSP), calcium, and phosphate from fish scales occurred simultaneously, and the chelation was also effectively performed. After a 6-h hydrolysis, the yield of FSP was 46.18%, and the dissolution rate of calcium was 49.53%. Under the optimal conditions (pH 7, chelation time of 25 min, and chelation temperature of 48 °C), a high chelation rate of 86.16% was obtained, with a calcium content of 81.8 mg/g. The results of UV absorption, Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and scanning electron microscopy (SEM) confirmed the successful chelation between FSP and calcium derived from fish scales. The –NH₂, –COO^–, N–H, C=O, C–H, and –OH groups in FSP participated in the formation of FSP-Ca.

Graphical Abstract