A novel antimicrobial ZnO nanoparticles-added polysaccharide edible coating for the preservation of postharvest avocado under ambient conditions

Abstract Edible coatings or films are considered effective and sustainable in preventing the waste of millions of tons of fruits and vegetables resulting from decay and deterioration. In this study, we propose a new edible coating formulation to preserve avocado. The edible coating consisted of film-forming mixed polysaccharides (chitosan and gum arabic) supplemented with non-toxic zinc oxide (ZnO) nanoparticles using the mixing method. ZnO nanoparticles with diameters ranging from 10 to 40 nm were synthesized using hydrothermal method. The prepared ZnO and ZnO/chitosan/gum arabic edible coatings were characterized by scanning electron microscopy, X-ray diffraction, and Fourier transform infrared spectroscopy. The results showed that the edible film coated on the avocado's surface was smooth and uniform with an even distribution of ZnO nanoparticles in the film matrix. The physicochemical properties of avocados, such as appearance and brightness; weight; firmness; and reducing sugar content significantly improved after coating with the ZnO/chitosan/gum arabic edible film as compared to the uncoated samples. The best protective performance was achieved when the coating’s optimum ZnO concentration was 0.3 % w/w. While the uncoated avocados rotted after seven days of storage in room temperature, the coated avocados remained fresh under similar storage conditions.