Chitosan–graphene oxide films as a promising packaging material for the preservation of fresh plums ( <i>Prunus salicina</i> Lindl.)

This study investigated the properties of bio-based films composed of chitosan (CH) at concentrations of 1.25% and 1.5%, incorporated with various amounts of graphene oxide (GO) (0, 0.5, 1.0, 1.5, and 2.0%), to develop films for fresh plum preservation. The results showed that films containing low concentrations of GO (0.5-1.0%) exhibited high transparency, whereas higher GO content (1.0-2.0%) led to a significant reduction in transparency. The addition of GO increased the surface roughness of the films. It caused noticeable color changes: brightness decreased, the characteristic reddish-yellow hue of pure chitosan was lost, resulting in darker and less vibrant films. Furthermore, the CH-GO films demonstrated relatively good near-UV blocking ability, allowing only visible light in the yellow to red spectrum to pass through. The incorporation of GO slightly reduced the water absorption and solubility, while significantly decreasing the water vapor permeability of the material (by 47.09-50.58% compared to the control film). In terms of mechanical properties, the film containing a low GO concentration (1.0%) exhibited a markedly higher tensile strength (increase 1.41 times) and an improved elongation at break (increase 2.53 times) compared to the control film. Although the antioxidant activity of GO-containing films showed a slight decline, the antibacterial performance was considerably enhanced, particularly against <i>E. coli</i>, with the inhibition zone diameter increasing by 26.66-35.84% compared to the control film. Experimental storage of fresh plums showed that the CH-GO film helped maintain fruit freshness and gloss, preventing spoilage for up to 10 days. Additionally, after 10 days, the film reduced weight loss (by 21.60-72.53% compared to the pure chitosan film group and 16.10-42.63% compared to the control group), slowed color changes, stabilized pH, maintained soluble solid content (reducing the loss by up to 10.54% compared to the control group), and preserved total acidity throughout the storage period. Based on these findings, CH-GO composite films can be considered a promising packaging material for the preservation of fresh produce.