Preparation and characterization of cinnamon essential oil Pickering emulsion stabilized by zein/carboxylated cellulose nanocrystals composite nanoparticles

The composite nanoparticles labeled as ZCP/C–CNC were synthesized by the combination of zein colloidal nanoparticles (ZCP) and carboxylated cellulose nanocrystals (C–CNC). The effects of the mass ratio of ZCP to C–CNC on the particle size, polydispersity index, ζ-potential, surface wettability and microstructure of ZCP/C–CNC were studied. The ZCP/C–CNC were used to stabilize cinnamon essential oil (CEO). The effects of ZCP/C–CNC on the properties of Pickering emulsions were investigated, including the interfacial tension, stability, encapsulation efficiency (EE), interfacial structure and antibacterial activity. With increasing of ZCP, the average particle size of ZCP/C–CNC firstly decreased and then increased, which was the smallest (196 nm) when the mass ratio of ZCP to C–CNC was 1. Scanning electron microscopy (SEM) showed that the structure of composite nanoparticles was featured that C–CNC layers wrapped ZCP. Confocal laser scanning microscope (CLSM) showed that CEO was effectively encapsulated by ZCP/C–CNC. When the mass ratio of ZCP to C–CNC was 1, the three-phase contact angle of the nanoparticle was 89.65°, showing the best surface wettability. And the CEO Pickering emulsion stabilized by this nanoparticle exhibited the smallest average particle size. It also showed the best stability and the best antibacterial activity against E. coli, S. aureus and S. putrefaciens. The EE of composite nanoparticles for CEO was significantly higher than that of pure ZCP or C–CNC particles, which all exceeded 91%. The Pickering emulsions stabilized by ZCP/C–CNC provided a promising alternative for the delivery of antimicrobial essential oils in the food, active packaging material and other related industries.