Molecular interactions between curcumin and diverse-source type Ⅰ/II gelatins: Complex fabrication and utilization in pickering emulsion systems

This study systematically compared the interactions between gelatins derived from different collagen sources (fish and bovine, corresponding to type I and type II collagen) and curcumin (Cur), focusing on the structural and interfacial properties of the resulting complexes. Four gelatin-Cur complexes (fish/bovine type I and II) were prepared via pH cycling, all achieving encapsulation efficiencies exceeding 80%. Particle size and zeta potential analysis showed that type I gelatin (FGI: 632.51 nm, −18.53 mV; BGI: 664.47 nm, −17.22 mV) had smaller particle sizes and higher absolute zeta potentials than type II gelatin (FGII: 747.13 nm, −16.69 mV; BGII: 764.13 nm, −15.02 mV). Upon complexation with Cur, these gelatin-Cur complexes showed increased interfacial contact angles (80.28°–89.26°) and equilibrium surface tensions (56.28–63.61 mN/m), while the dynamic oil–water interfacial tension continuously decreased and reached equilibrium within 300 s. Fluorescence quenching of gelatin by Cur followed a static mechanism, and complex formation was primarily driven by hydrophobic interactions, hydrogen bonding, and electrostatic forces. The binding affinity (Ka) followed the order: FGI/Cur (7.59 × 10 6  L/mol) > BGI/Cur (7.44 × 10 6  L/mol) > FGII/Cur (6.91 × 10 6  L/mol) > BGII/Cur (6.42 × 10 6  L/mol), consistent with molecular docking results. Cur preferentially localized to the Ser129–Glu135 region of type I gelatin and the Asn179–Ser183 region of type II gelatin. The resulting gelatin-Cur particles effectively stabilized Pickering emulsions. After storage, the TBARS values of gelatin-Cur stabilized emulsions were at least 50.82% lower than those of gelatin-stabilized emulsions. Rheological analysis revealed G' > G'' (elastic-dominated) and shear-thinning behavior, with Cur loading further improving the elastic modulus. These findings provide a theoretical basis for the utilization of by-product gelatin in combination with Cur.