Chitosan/tamarind gum-based functional composite films integrated with copper metal-organic frameworks and anthocyanin for shrimp freshness monitoring

Purpose The purpose of this study is to prepare chitosan (CS)/tamarind gum (TG) composite films integrated with copper metal-organic framework and investigate its shrimp freshness monitoring ability. Design/methodology/approach Anthocyanins were extracted from black goqi berries using solvent extraction. Copper metal organic framework (Cu-MOF) was synthesized by a hydrothermal method, after which the two materials were added to a film-forming solution of CS and TG co-mingled and the film was formed using the casting method. The particle size distribution, adsorption properties, morphology, ammonia-responsive properties and antioxidant properties of the films prepared from Cu-MOF were investigated. Findings The successful synthesis of the copper metal-organic framework was verified by scanning electron microscope, Fourier transform infrared spectroscopy, thermogravimetric analysis and Bruno Emmett Taylor, and the incorporation of Cu-MOF into the composite film significantly improved the ammonia sensitivity, antioxidant properties, light transmittance and mechanical properties. When stored at 4°C, the composite film has excellent color stability. Finally, the film was applied to shrimp freshness monitoring, when the total volatile basic nitrogen value of shrimp is above 30 mg/100 g, the color of the film changed from purple (fresh shrimp) to brown (spoiled shrimp), successfully indicated spoilage of shrimp. Originality/value Black goji berry anthocyanin and copper-metal organic framework complexes were used as indicators for the preparation of smart packaging films with high ammonia response performance.