Fabrication of Pickering emulsions stabilized by coconut globulin-sodium alginate complexes: The role of electrostatic assembly and oil phase fraction in microstructure and rheology

Coconut globulin (CG) recovered from defatted coconut meal was complexed with sodium alginate (SA) to fabricate CG-SA complex-stabilized Pickering emulsions. Optimal preparation conditions (CG:SA mass ratio 1:2, pH 7.0, ionic strength 30 mM) were determined via orthogonal experiments based on single-factor optimization. Fourier transform infrared spectroscopy confirmed complexation through hydrogen bonding and electrostatic interactions. The CG-SA complex exhibited enhanced surface hydrophobicity, facilitating interfacial adsorption. The oil phase fraction (40%-80%) critically governed emulsion properties. At 40%-50% oil, emulsions displayed fluid-like behavior (G″ > G′) and high emulsifying activity, but showed obvious phase separation within 24 h. At 60%-70% oil, emulsions exhibited no obvious phase separation over 120 h of storage and maintained stability upon inversion. At 80% oil, the system transitioned toward a gel-like network (G′ > G″ at low frequencies) but suffered from severe oil separation (38.6%) upon centrifugation, indicating interfacial film failure. These findings demonstrate that CG-SA complexes can serve as effective Pickering stabilizers for coconut oil-based emulsions, with 60%-70% oil identified as the optimal range for long-term stability. This work provides a reference for utilizing coconut by-products in the development of clean-label emulsion products. Highlights : • A Pickering emulsion was stabilized by a coconut globulin-sodium alginate complex. • Optimal conditions for emulsion were CG:SA=1:2, pH 7.0, ionic strength 30 mmol/L. • A 40%-50% oil fraction displayed high emulsifying activity. • A 60%-70% oil fraction showed long-term stability. • An 80% oil fraction induced a gel network but with severe oil separation.