Films and coatings from pequi mesocarp incorporated with nano-ZnO: Properties and capacity to increase mango shelf life

Abstract

The need for new packaging technologies to decrease environmental pollution, while contributing to food preservation is driving the development of innovative materials using renewable sources and active substances. Pectin extracted from pequi (Caryocar brasiliense Camb.) mesocarp was used to produce films and coating incorporated with ZnO nanoparticles (nano-ZnO). Films incorporated with different concentrations of nanoparticles (0.25%, 0.5%, and 1.0%) were characterized by their packaging performance, structure, antimicrobial activity, and biodegradability. Control pectin coatings and coatings incorporated with nanoparticles were applied to mango fruits to estimate their capacity to slow down the ripening process. The incorporation of nano-ZnO in pectin films affected some of the packaging properties, such as tensile strength, and water vapor permeability, which decreased. In the higher concentration of nano-ZnO tested, the maximum tensile strength was 1.54 MPa, the strength at break was 0.82 MPa, and elongation at break was 14.45%. The water vapor permeability decreased from 10.57 to 8.85 g.mm/m².dia.kPa adding 1.0% of nano-ZnO. The characterization of the film’s structure demonstrated that nano-ZnO had a physical interaction with the pectin matrix. The antimicrobial assay showed that control pectin films could inhibit microorganisms (Staphylococcus aureus, Pseudomonas aeruginosa, and Salmonella Enteritidis). ZnO incorporation in films did not present significant differences probably due to the low concentrations applied. All the film formulations tested were completely biodegraded in 2 days in soil and all coatings could slow down the ripening process of mango fruits within 12 days of analysis. Control and ZnO incorporated formulations are promising for use as biodegradable films for food packaging and fruit coatings.