Gelatin-based smart film incorporated with nano cerium oxide for rapid detection of shrimp freshness

A novel and convenient nano cerium oxide peroxidase mimic smart film for rapid detection of hypoxanthine (HX) concentrations to predict shrimp freshness was reported. Xanthine oxidase was incorporated into the smart film to react with HX and produce H2O2. Cerium oxide nanoparticles (CeNPs), as redox amplifiers and chromogenic agents, were oxidized by H2O2 to produce regular color changes to quantify HX concentrations. All components entrapped in a three-dimensional gelatin matrix crosslinked with glutaraldehyde. The nanostructure of CeNPs and the feasibility of their use as multifunctional nanozymes for HX detection were explored, as were the effects of CeNPs addition on the physical and colorimetric properties of the film. The morphology and HX sensitivity were also characterized, and their feasibility in monitoring shrimp freshness was further verified. The results showed the gelatin/glutaraldehyde film with 25% CeNPs had good performance. This film had a high sensitivity, with a linear range of HX detection of 6.2-200 mu M and the lower limit of detection of 35 mu M. Furthermore, the film could determine the shrimp freshness level with a predictive accuracy of approximately 0.9223. This method can be applied for packaging food as a freshness indicator because of its convenience, high sensitivity, and low cost.