Complex coacervation of zein-chitosan via atmospheric cold plasma treatment: Improvement of encapsulation efficiency and dispersion stability

Zein-polysaccharide complex coacervations were modified using atmospheric cold plasma (ACP) technology in order to decrease zein's hydrophobicity and consequent aggregation. The ACP-induced interaction between zein and chitosan in 70% ethanol-water solution was investigated. To evaluate the application potential of the modified complex in nutrition delivery, the encapsulation efficiency and dispersion stability of resveratrol-loaded nanoparticles were investigated. It was found that the novel zein-chitosan complex coacervation re-assembled in 70% ethanol-water solution after ACP treatment, displaying smaller particle sizes (from 1191 nm to 370 nm) and higher conductivity (from 36.6 ds/cm to 43.1 ds/cm) than non-ACP-treated samples. UV-vis spectrum, IR, AFM and SDS-PAGE analysis demonstrated that the ACP treatment caused conformational changes and unfolding of the zein polypeptide chain, increased hydrogen bonding and electrostatic interactions between zein and chitosan. No effects were observed on the primary structure of zein. The aggregation of complex coacervations was also reduced after treatment. With ACP treatment (40 V), resveratrol-loaded nanoparticles showed higher encapsulation efficiencies (from 51.8% to 82.7%) and better dispersion stability compared to untreated samples. A possible assembly mechanism between zein and chitosan under ACP exposure is proposed. These findings clarify the interaction between protein and polysaccharide under ACP exposure and demonstrate the promise of ACP technology in modifying zein-chitosan complex coacervation as a promising delivery carrier in the functional food field.