Abstract:Smart indicator films were prepared by the solution casting method with gelatin as the film-forming substrate，purple cabbage anthocyanin as the freshness indicator，and nano-titanium oxide（TiO2）as the ultraviolet（UV）protective agent.The effects of different content of nano-TiO2 on the physical properties，light stability，and mechanical properties of the indicator films were characterized.The results showed that the introduction of TiO2 improved the light stability，mechanical properties，and water vapor permeability of the film.The film prepared with the TiO2 addition at 1% showed the elongation at break of 21.55%，the tensile strength of 22.73 MPa，the water vapor transmission coefficient of 3.885 g/（m·s·Pa），and strong light stability，demonstrating the best overall performance.The results of Fourier transform infrared spectroscopy and scanning electron microscopy showed that new hydrogen bonds were formed between gelatin，anthocyanin，and TiO2.Accordingly，the network structure of the film became denser.In addition，the indicator film with the best overall performance was employed to monitor the freshness of shrimp（4 ℃），which showed obvious color changes during the experimental period.The freshness was graded based on the color changes.The correlation analysis showed a significantly positive correlation between the color difference（ΔE）of the indicator film and the content of total volatile basic nitrogen（R2=0.913 3），indicating that the indicator film enabled the visual monitoring of the freshness of fresh shrimp in real time.