Enzymatic hydrolysis of white-cheek shark skin gelatin: Optimization, structural transformations, functional characteristics, and antioxidant potential

This study investigates the enzymatic hydrolysis of white-cheek shark (Carcharhinus dussumieri) skin gelatin using Alcalase to produce antioxidant peptides. Response surface methodology was employed to optimize enzyme-substrate ratio (E/S) and hydrolysis time. The optimal conditions, with an E/S of 4.8% for 133 min, achieved the highest degree of hydrolysis (DH) of 23.4%, as well as maximum DPPH radical scavenging activity (56.8%) and FRAP value (0.24 mg AAE/g). Subsequent evaluations of hydrolyzed (WCSG-H) and non-hydrolyzed gelatin (WCSG) revealed significant differences in their properties (p<0.05). Specifically, gel electrophoresis showed molecular weight fractions of 72–165 kDa for WCSG and <8 kDa for WCSG-H, while amino acid profiling indicated high levels of glycine, proline, and alanine in both samples. ATR-FTIR spectroscopy demonstrated that enzymatic hydrolysis led to a more disordered secondary structure in WCSG. Furthermore, WCSG exhibited superior emulsion activity, foaming capacity, and foam stability, though differences in emulsion stability were not statistically significant (p>0.05). In contrast, WCSG-H showed significantly higher solubility (97.7%) and antioxidant capacity (56.8% DPPH radical scavenging activity and FRAP of 0.24 mg AAE/g) compared to WCSG (85.22%, 52.82%, and 0.08 mg AAE/g, respectively). Therefore, these findings suggest that both WCSG and WCSG-H are promising natural antioxidants for functional food applications.