Effectiveness of cellulose and chitosan nanomaterial coatings with essential oil on postharvest strawberry quality.

Polysaccharide materials, including bagasse cellulose nanocrystals (BCNCs), chitosan nanofibers (ChNFs), and sodium alginate (SA), were blended with oregano essential oil (OEO) to make single- and multi-polysaccharide edible coating suspensions. The prepared suspensions were spray-coated on strawberry surface to form thin films with thickness varying from about 570 to 790 nm for single-polysaccharide coatings and 690-930 nm for multi-polysaccharide coatings. The coatings made with multi-polysaccharide were more effective in inhibiting fungal growth compared with single-polysaccharide coatings. Strawberry treated with SA/BCNC/ChNF/OEO formulation had only 10.8 % weight loss after nine days of storage. In contrast, uncoated and single-polysaccharide coated strawberries had >37.0 % and 28.6 % weight loss, respectively. In addition, the SA/BCNC/ChNF/OEO coating retained desired moisture, respiration rate, stiffness, firmness, and appearance properties of strawberry due to its gas barrier properties resulting from the entangled matrix structure. These results suggest that the multi-polysaccharide suspensions with OEO have a high potential for application as edible coatings for retarding senescence of strawberries.

Comparative performance of bio-based coatings formulated with cellulose, chitin, and chitosan nanomaterials suitable for fruit preservation.

Sustainable nanomaterials (SNMs) from wood, sugarcane and crab shell were prepared and used to coat selected fruits. The properties of SNMs and selected fruits were characterized and strawberry was used as an example to test antifungal activity and freshness preservation of the SNMs. The SNMs with their nano-structured morphology form strong shear-thinning dispersions for easy spraying on fruit surfaces. The fruit surface free energy was influenced by its surface morphology, predominant surface wax components, and cutin monomers. The antifungal activity of SNMs was influenced by their surface functional groups and particle size (crystals vs fibers). The coblend of wood nanocrystals (WCNCs) and chitosan nanofiber (CSNFs) exhibited the best antifungal property, which was comparable with the performance of the fungicide thiabendazole (80 mg L-1). The weight loss and color change of the WCNC/CSNF coated strawberries decreased by nearly half compared with the control samples, showing coating effectiveness on preserving fruit freshness.