Development of a Phycocyanin–Copper-Loaded Gelatin–Chitosan Active Forming Film Solution and Its Application in Fruit Quality Preservation
Abstract
Phycocyanin–Cu2+-loaded gelatin–chitosan composite films (Gel/Cu@PC/Ch) were developed as active packaging materials to address the postharvest deterioration of fresh produce. A series of composite films with varying chitosan (Ch) concentrations (0.1%, 0.5%, 1%, 5%, w/v) were systematically fabricated and characterized. Scanning electron microscopy (SEM) revealed that the Gel/Cu@PC/Ch0.5 film (0.5% chitosan) exhibited smooth, pore-free, and crack-free surface and cross-sectional morphologies, while a higher chitosan dosage (5%) triggered severe structural cracking. Gel/Cu@PC/Ch0.5 achieved the maximum water contact angle of 101.13 ± 9.59°, demonstrating superior surface hydrophobicity. All composite films possessed outstanding UV-shielding capacity; meanwhile, ABTS and DPPH free radical scavenging rates rose gradually with increasing chitosan content, reaching 79.71 ± 0.72% and 84.91 ± 1.31% at 5% Ch, respectively. In antibacterial assessments, Gel/Cu@PC/Ch0.5 showed effective inhibition against both Staphylococcus aureus and Escherichia coli, with inhibition zone diameters of 13.83 ± 0.42 mm and 14.93 ± 0.83 mm, respectively, owing to the synergistic bactericidal effect of Cu2+ and chitosan. In grape preservation trials conducted over 12 days, Gel/Cu@PC/Ch0.5 wrapped grapes exhibited the lowest weight loss (3.60 ± 0.30%), retained the highest residual firmness (316.16 ± 13.81 g) and total soluble solids (TSS), and maintained a significantly higher TAC value of 0.71 ± 0.12 nM after 12 days of storage, with no visible microbial spoilage or severe shriveling observed throughout storage. These results demonstrate that the Gel/Cu@PC/Ch0.5 composite film achieves a desirable integration of moisture barrier performance, antioxidant activity, and broad-spectrum antibacterial efficacy, offering a scalable and biodegradable platform for active food packaging in fresh fruit preservation.