Monitoring of Oxygen Using Colorimetric Indicator Based on Graphene/TiO2 Composite with First-order Kinetics of Methylene Blue for Modified Atmosphere Packaging

Abstract

Oxygen is crucial in food preservation and food spoilage. For the purpose of monitoring intact of modified atmosphere packaging (MAP) by nondestructive testing and controlling the reaction rate during recovery stage, we report a convenient and visual colorimetric oxygen indicator based on a graphene /titanium oxide composite, incorporating glycerol, methylene blue (MB), hydroxyethyl cellulose (HEC) and poly (vinyl alcohol) (PVA). The graphene/titanium oxide (GNT) composite was synthesized through a modified Hummers synthesis of graphene oxide, followed by the hydro-thermal treatment with butyl titanate without using any reducing agent, then the morphology and structure characteristics were analyzed by XRD, FT-IR, Raman spectra, UV-vis, SEM and TEM. According to the performance tests using UV-vis and CIElab, the indicator demonstrated the pseudo first-order kinetics of MB for modified atmosphere packaging in detecting stage. It is confirmed with the results that the prepared colorimetric indicator can actually detect the intact of MAP without destruction. Additionally, the reaction time of indicator in recovery stage can be controlled by changing the concentration of MB, because of pseudo first-order kinetics.