Bio-based nanomaterial suspensions as sprayable coatings for maintaining blueberry postharvest quality

The growing concerns about postharvest fruit spoilage demand sustainable active coating materials with high performance. In this work, bioactive spray coating suspensions were developed for the postharvest preservation of blueberries using chitosan, cellulose, and lignocellulose nanofibers (ChNFs, CNFs, and LCNFs), sodium alginate (SA), and tea tree essential oil (TTO). Characteristics, including the rheological properties of coatings and the effect on physicochemical postharvest quality parameters of blueberry fruit were investigated. The nanomaterials and SA were shown to make stable and sprayable coating suspensions with high surface charge (zeta potential value of −61.3 mV), shear thinning behavior, steady viscosity, and outstanding viscoelastic behavior from their ability to restore fibrous network structure and ion strength of SA to inhibit nanofibers aggregation. The coatings with LCNFs and SA were more effective in retarding moisture loss of postharvest blueberries during storage compared with coatings without LCNFs and SA. Blueberries coated with ChNF/LCNF/SA/TTO had a soluble solids content (SSC) increase of 16.2% after 15 storage days, while uncoated and other coated blueberries had more than a 21.7% SSC increase. In addition, the ChNF/LCNF/SA/TTO coating had an entangled matrix structure and enhanced hydrophobicity, improving gas barrier performance on the blueberry surface. As a result, the coating was able to preserve the moisture, stiffness, firmness, and individual sugar contents of blueberries during storage. Utilizing nanomaterials and other natural polysaccharides in coatings can offer an economically feasible and sustainable approach for functionalizing biomass materials to preserve fruits.