Fabrication of surfactant-stabilized zein nanoparticles: A pH modulated antisolvent precipitation method

•Protein-nanoparticles were fabricated from zein using antisolvent precipitation.•pH control during the preparation procedure is important for stable systems.•The influence of environmental stresses on their charge and stability was measured.•Particle size and polydispersity could be controlled by thermal processing.

Zein nanoparticles were fabricated by a pH-modulated antisolvent precipitation method using a food-grade non-ionic surfactant (Tween 80) as a stabilizer. The nanoparticles formed had a core-shell structure consisting of a zein core with a diameter around 78 nm and a surfactant shell with a thickness around 4 nm. The electrical charge on the nanoparticles was mainly determined by zein, going from positive at low pH to negative at high pH with a point of zero charge near pH 5. The nanoparticles were stable to aggregation from pH 2 to 4.5 (high positive charge) and from pH 6.5 to 8 (high negative charge), but they aggregated from pH 5 to 6.5 due to weak electrostatic repulsion. The nanoparticles were susceptible to aggregation at high ionic strengths (≥ 50 mM NaCl) at both pH 4 and 7. They also exhibited some aggregation upon heating (90 °C for 120 min) at pH 4, but were relatively stable at pH 7. The core-shell nanoparticles formed in this study have potential as food-grade delivery systems for encapsulating, protecting, and releasing bioactive molecules in food and pharmaceutical formulations.