Fabrication of chitosan/guar gum/polyvinyl alcohol films incorporated with polymethoxyflavone-rich citrus extracts: Postharvest shelf-life extension of strawberry fruits

Abstract

In this study, chitosan/guar gum/polyvinyl alcohol (CGP) matrix (CGPC) films with different concentrations of polymethoxyflavone (PMF)-rich citrus extracts were developed. The results showed that these films had 11.90–16.77 μm of thickness, 32.53 %–41.53 % of moisture content, 33.16 %–121.64 % of water solubility, 2.14–3.18 × 10−10 g m−1 s−1 Pa−1 of water vapor permeability, 65.57 %–148.74 % degree of swelling, 6.08–16.05 MPa of tensile strength and 28.25 %–62.82 % of elongation at break. SEM and TEM observations indicated that the content of PMF-rich extracts affected the distribution and structure of the film matrix, which were confirmed by FT-IR and XPS outcomes. TGA-DTG and DMTA analysis revealed that the presence of 0.02 % PMF-rich extracts enhanced the thermal stability and cross-linking density of the film. Moreover, the incorporation of the PMF-rich citrus extract significantly improved the DPPH radical scavenging rate (increased from 26.22 % to 94.19 %) and antifungal property (against Rhizopus stolonifera in vitro). Furthermore, the inclusion of citrus extracts in the CGP matrix effectively inhibited the deterioration and weight loss of strawberry fruits. Thus, the CGP film incorporated with PMF-rich citrus extract has significant potential as an active packaging material for preserving fresh fruit.