Zinc oxide nanoparticles and periodate oxidation in developing pH sensitive packaging film based on modified gelatin

Abstract

Abstract Background and objective: Petroleum-based packaging materials are extensively utilized in the food industry as they are cost-efficient, possess high stability against gases and moisture, and are easily processable in both rigid and flexible states. However, considering the environmental problems with these synthetic plastics, many researchers have focused on their substitution with biodegradable materials, especially biopolymers (proteins, polysaccharides, lipids, and their combinations). Materials and Methods: Response surface methodology was used to develop pH-sensitive gelatin-based films containing red cabbage extract, zinc oxide nanoparticles (ZnONPs; 0-0.05% of gelatin), and oxidized sucrose (OS; 0-15% of gelatin) as a cross-linker. Results: Film solubility decreased from 100% in the control to 34.57% in films containing higher OS levels. The minimum WVP of the cross-linked gelatin films was obtained at 10% OS and high levels of ZnONPs. Antioxidant activity of the gelatin-based films was reinforced by both ZnONPs and OS. Higher concentrations of the cross-linker caused a decline in opacity, whereas ZnONPs boosted the films opacity. With the goal of minimizing solubility and WVP while maximizing antioxidant capacity, the optimum film treatment was obtained at 0.043% ZnONPs and 11.45% OS. The effect of ZnONPs on tensile strength and elongation at break of the optimum sample was more pronounced in comparison with OS, though the combined use of these species resulted in packaging films with enhanced TS and low EB. Cross-linking of gelatin chains was observed with porous and dark morphology via SEM images. Three decomposition stages were obtained in thermal analysis of polymeric films. The thermal stability of the optimum treatment was higher than the control and it had stronger antimicrobial activity against Staphylococcus aureus than Escherichia coli. The optimum film showed color changes from reddish-purple to blue-green in the pH range of 3-12 and was colorless at around neutral pH. Conclusion: In summary, we reinforced the gelatin film structure and achieved functional, pH-responsive characteristics in a novel, intelligent, and active packaging material.

Keywords: Cross-linked gelatin; Periodate oxidation of sucrose; Zinc oxide nanoparticle; pH respofilmnsive