Dragon fruit peel pigment extraction residue based intelligent and biodegradable film for indicating milk freshness

pH-responsive intelligent films for food freshness monitoring have attracted a great deal of attention in recent years. In this study, dragon fruit peel was used to develop a new type of active and functional film. The film was prepared by using residues extracted from dragon fruit peel (RPP) as the matrix, Curcumin (Cur) as the active ingredient and ZnO-NPs as the antibacterial material. The effect of the incorporation of Cur and ZnO-NPs on the properties of the films was studied. The addition of Cur increased the oxidation resistance of the films (more than 90 %), and ZnO-NPs increased the bacteriostasis and hydrophobicity of the films (water contact angle (WCA):122.00°). The colorimetry response of the RPP/Cur/ZnO-NPs film was performed, and the color of the film changed from brown to tawny to yellow. These properties highlight the potential of the RPP/Cur/ZnO-NPs film for practical applications, indicating its potential applications as smart packaging materials for the food industry. Therefore, the RPP/Cur/ZnO-NPs composite film based on dragon fruit peel can be used to monitor the freshness of milk, and to a certain extent contribute to the sustainable value of dragon fruit by-products in the food industry.