Development of active and intelligent packaging by incorporating betalains from red pitaya (Hylocereus polyrhizus) peel into starch/polyvinyl alcohol films

This study aims to develop active and intelligent packaging films based on starch/polyvinyl alcohol incorporated with betalains-rich red pitaya (Hylocereus polyrhizus) peel extract. The microstructure, physical and functional properties of the films with different contents of the extract (0.25, 0.50 and 1.00 wt% on starch basis) were measured. Results showed betacyanins were the main components in the extract, which presented significant color changes under alkaline conditions. Scanning electron microscopy observation revealed the compactness of the films was improved by the extract addition. Fourier transform infrared spectroscopy revealed that betacyanins in the extract could interact with starch, polyvinyl alcohol and glycerol through hydrogen bonds. The incorporation of the extract enhanced the water vapor barrier and ultraviolet–visible light barrier ability, and mechanical, antioxidant and antimicrobial potential of the films. The film containing 1.00 wt% of the extract was more sensitive to ammonia than other films. When applied to monitor the freshness of shrimp, the film containing 1.00 wt% of the extract presented visible color changes due to the accumulated volatile nitrogen compounds during the spoiling process of shrimp. Our results suggest the film containing 1.00 wt% of the extract can be used as active and intelligent packaging in food industry.