Fabrication, characterization, and 3D printing of high-internal phase Pickering emulsion stabilized by heat-treated copra protein and calcium composite

HCP-Ca nanoparticles were prepared by incorporating varying concentrations of CaCl₂ into heated copra protein (HCP). The results showed a positive correlation between Ca²⁺ concentration and turbidity, indicating greater HCP aggregation with increasing Ca²⁺ levels. Microscopy analysis revealed that HCP-Ca nanoparticles had a rough surface morphology. Intermolecular forces such as disulfide bonds, hydrophobic interactions, and hydrogen bonds were key in the conformation of HCP aggregates, with calcium ions enhancing stability by forming salt bridges. HCP-Ca nanoparticle-based high internal phase Pickering emulsions (HIPPEs) were also fabricated using homogenization-centrifugation treatment. The nanoparticles showed contact angles of 87.8° to 98.3°, particle sizes between 80.42 and 80.95 nm, and the HIPPEs had zeta potentials ranging from -23 to -39 mV. The addition of Ca²⁺ enhanced stability by forming salt bridges, reducing particle size, and altering size distributions. Rheological and texture analysis showed that Ca²⁺ addition significantly improved the viscoelasticity of HCP-Ca nanoparticle-based HIPPEs, as well as increasing hardness and adhesiveness. Optical microscopy and magnetic imaging techniques revealed details about emulsion formation and oil-water distribution in HCP-Ca nanoparticle-based HIPPEs. The excellent printing stability and structural versatility of HCP-Ca nanoparticle-based HIPPEs allowed the formation of complex 3D structures, offering a valuable approach for fabricating processable and editable HIPPEs from waste materials. This paper aims to develop a food-grade copra protein-based Pickering HIPPE and explore differences in fabrication methods, providing new insights into the design of innovative Pickering stabilizers.