Radiation Synthesis of Edible Coating Films of Nanocurcumin Based on Carboxymethyl Chitosan/Polyvinyl Alcohol to Extend the Shelf Life of Sweet Orange "Valencia"

Edible coating CMCS/PVA/Cur and films were prepared using gamma-irradiation to extend the shelf-life of sweet orange "Valencia" fruits. Water-soluble CMCS was synthesized by carboxymethylation of chitosan. Extraction of curcumin from turmeric powder and conversion to Cur-NPs of 76-108 nm average size was achieved. CMCS/PVA/Cur membranes were prepared via the casting method and gamma-irradiation technique. The chemical properties were studied by FTIR and XRD as well as studying the effect of irradiation dose on gel content, water swelling, and mechanical properties. FTIR and XRD results confirm the interaction between functional groups of Cur-NPs with CMCS/PVA polymer chains. Results indicated that the membrane possessed good tensile strength and gel content of 97.4% and the swelling was significantly decreased with increasing the irradiation dose. Fruits were dipped in CMCS/PVA/Cur coatings at different concentrations of Cur-NPs (0, 2.5, 5, and 10%) and stored at room temperature of 65-70% RH for about 70 days. The efficiency of coatings was assessed by decay (%), weight loss (%), pH, vitamin C content, total soluble solids (TSS), titratable acidity (TA), and TSS/TA ratio. Quality characteristics of coated fruits were better than uncoated fruits especially the coating solution of 2.5% Cur-NPs provides accepted freshness and quality. No decay was noticed for the coated fruits till 56 days, whereas the control exhibited decay of 36%. The prepared coating solutions possessed good antimicrobial activity and cytocompatibility characteristics and showed normal viability even at all concentrations. Results demonstrated a promising packaging material to extend the shelf life and freshness of orange fruits.