Characterization of nanostructured chitosan-PVA films and their effects on blueberries during storage

Abstract

The use of nanotechnology in coatings has become a topic of growing interest. In this work, the effect of adding chitosan nanoparticles (NP) into chitosan/polyvinyl alcohol (PVA) coatings was studied. The cross-section of film micrographs obtained by scanning electron microscopy (SEM) showed a coarse surface for CS100, a smooth surface for PVA100 and blends morphology like CS100, except for the 33NP30PVA37CS and 33NP40PVA27CS films which were similar to PVA100. Fourier-transform infrared spectroscopy (FTIR) revealed interaction between the PVA and chitosan functional groups, which was reflected in the thermal and mechanical properties. The NP enhanced thermal stability and rigidity (Young´s modulus = 54.79 ± 3.94 MPa) with the highest crystallinity (52.71 %) of the films, and showing 100 % in vitro inhibition against B. cinerea for the 33NP67CS formulation. The postharvest evaluation for coated fruit showed a decrease in weight loss (< 5 %) and firmness (between 0.24–2.47 N). On the other hand, anthocyanin content increased during storage with values from 7 to 34 mg/100 g on day 8. Disease incidence was between 23 and 30 % and severity near 25 %. The nanostructured coating formulations preserve blueberry quality, making them an attractive option for sustainable food packaging.