Visible Colorimetric Oxygen Indicator Based on Ag-Loaded TiO2 Nanotubes for Quick Response and Real-Time Monitoring of the Integrity of Modified Atmosphere Packaging

Oxygen indication is a new technique for non-destructive testing (NDT) of modified atmosphere packaging (MAP). Damage may occur at any time during the transportation and storage of MAP, resulting in increased oxygen concentration. This may lead to food quality decline and even food spoilage. However, it is difficult to judge whether the package is undamaged without professional equipment. A visible colorimetric oxygen indicator that can accurately identify an intact packaging system to ensure food safety is reported. The indicator consists of an Ag-loaded titanium dioxide nanotube (Ag-TNT), glycerol, methylene blue (MB), and hydroxyethyl cellulose (HEC). According to X-ray diffraction, X-ray photoelectron spectroscopy, transmission electron microscopy, Brunauer-Emmett-Teller analysis, diffuse reflectance spectroscopy, and UV-vis results, the Ag-TNT showed efficient photocatalytic performance, increased specific surface area (from 85 to 227 m(2) g(-1)), and an increased band gap of 3.30 eV. These results dramatically improved the performance of Ag-TNT as an oxygen indicator. Additionally, it demonstrated two outstanding properties: blocking indicator response to natural light (wavelength > 380 nm) and shortening the bleaching time during activation. Such an oxygen indicator can considerably enhance the accuracy of NDT for packages. Furthermore, it can be used in the packaging of different foodstuffs, ensuring food safety.