Pickering emulsions stabilized by similarly charged shellac nanoparticles and carboxymethyl starch: Co-assembly mechanism and environmental stability

Similarly charged SNP and CMS co-assemble via non-electrostatic interactions. • SNP/CMS mass ratio precisely tunes wettability for dense interfacial coverage. • LAOS reveals a robust gel network with pronounced non-linear yielding behavior. • Emulsions show high resilience to salt (800 mM), freeze-thaw, and heat (50 °C). • A food-grade strategy for robust Pickering emulsions is provided. : Pickering emulsions with stability under processing and storage conditions are of significant interest for structured food systems. In this study, Pickering emulsions were stabilized using similarly charged shellac nanoparticles (SNP, −30.5 mV) and carboxymethyl starch (CMS, −40.1 mV). Despite electrostatic repulsion, FTIR, urea-disruption, and pyrene fluorescence analyses suggested that hydrogen bonding and hydrophobic association contributed to SNP/CMS co-assembly. By adjusting the SNP/CMS mass ratio, interfacial wettability was precisely tuned, with the three-phase contact angle increasing from 76.9° to 103.5°, thereby promoting particle adsorption at the oil–water interface and the formation of a compact interfacial layer. The resulting emulsions exhibited self-supporting three-dimensional networks with elastic-dominated viscoelasticity (G′ > G″) and pronounced nonlinear yielding behavior under large-amplitude oscillatory shear (LAOS). These emulsions maintained high stability under freeze–thaw cycles and high ionic strength (up to 800 mmol/L NaCl). Thermal stability was maintained up to 50 °C. This study provides insight into the non-electrostatic co-assembly of similarly charged SNP/CMS complexes and offers a material-specific strategy for designing salt-tolerant structured Pickering emulsions.