Edible water barrier films prepared from aqueous dispersions of zein nanoparticles

Zein, a corn protein, is often used for preparing edible films and coatings. Since zein is insoluble in water, zein films and coatings are usually prepared by spraying or casting its aqueous ethanol solutions to a contact surface (Zsol films). However, the use of organic solvents in many food applications is unwanted. In this work, aqueous dispersions of zein nanoparticles were prepared by antisolvent precipitation from 90% v/v aqueous ethanol zein solutions. Zein films were then prepared by casting the dispersions in silicone molds and air–drying at 50 °C (Zdis films). The obtained films were characterized for morphology, FTIR analysis, mechanical, water barrier and optical properties, and were benchmarked against Zsol films. It was found that continuous zein films can be prepared out of aqueous dispersions of zein nanoparticles. Zdis films proved to have grainy morphology and higher surface roughness when compared to Zsol. Surface roughness of Zdis films was decreased when plasticizer was added. Water barrier properties of Zdis films were found to be comparable to Zsol films. No differences in mechanical properties were found between Zsol and Zdis film. Size of zein particles influenced morphology and optical properties of zein dispersion films.