Alkali-Induced Hydrolysis Facilitates the Encapsulation of Curcumin by Fish (Cyprinus carpio L.) Scale Gelatin

Curcumin-loaded alkali-induced fish scale gelatin (AFSG) was fabricated to evaluate its efficacy as a potential carrier for hydrophobic nutrients. In this study, the effect of the alkali hydrolysis period on the AFSG hydrolysate structure and corresponding curcumin loading efficiency have been elucidated. Results showed that alkali-induced degradation of gelatin yields different polymers with molecular weights (M) from 19319 to 3881 Da. Moderate alkali hydrolysis of fish scale gelatin exposes hydrophobic amino acids, enhancing hydrophobic interactions and increasing the proportion of these amino acids. This process also promotes a structural shift, favoring β-sheet formation while reducing α-helix content. Moreover, the curcumin loading efficiency of AFSG (2 h) (10.06 ± 0.27 μg/mL) was significantly higher than that of untreated gelatin (2.16 ± 0.39 μg/mL), while its excessive hydrolysis weakens hydrophobic interactions among hydrophobic amino acids, limiting their binding sites for curcumin. Fluorescence spectroscopy indicated that curcumin-induced fluorescence quenching in AFSG follows a static mechanism. Thus, the above results demonstrated AFSG's potential as an effective carrier for lipophilic nutrients with high encapsulation efficiency.