Gelatin/agar-based color-indicator film integrated with Clitoria ternatea flower anthocyanin and zinc oxide nanoparticles for monitoring freshness of shrimp

Gelatin/agar-based smart and functional freshness indicator films were fabricated using blue anthocyanin and zinc oxide nanoparticles (ZnO). The anthocyanin was extracted from butterfly pea (Clitoria ternatea) flower, and ZnO was synthesized using a simple hydrothermal method. The butterfly pea anthocyanin (BA) and ZnO were evenly dispersed in the polymer matrix to form a compatible film with the gelatin/agar polymer. The addition of BA and ZnO significantly increased the UV blocking properties and surface hydrophobicity without significant changes in the film's mechanical, thermal stability, and water vapor barrier properties. The BA and BA-added films showed excellent pH-responsive color-change properties as well as good color stability and reversibility. In addition, the composite film showed strong antioxidant and strong bactericidal properties, and the antioxidant function was mainly attributed to the BA, and the antibacterial function was attributed to ZnO. The functional and color indicator film was tested to monitor the freshness of shrimp. It showed distinctive color changes during storage, indicating the degradation of the quality of shrimp accompanied by the total volatile basic nitrogen (TVB-N).