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 to food preservation and food spoilage. For the purpose of monitoring the integrity of modified atmosphere packaging (MAP) by nondestructive testing and controlling the reaction rate during recovery stage, we reported on a convenient and visual colorimetric oxygen indicator based on a graphene/titanium oxide composite, incorporating glycerol, methylene blue (MB), hydroxyethyl cellulose, and polyvinyl alcohol. The graphene/titanium oxide composite was synthesized from 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 analysed by X‐ray diffraction, Fourier transform infrared, Raman spectra, ultraviolet‐visible spectroscopy, SEM, and TEM. Supported by the performance tests using ultraviolet‐visible spectroscopy and CIElab, the indicator demonstrated the pseudo first‐order kinetics of MB for MAP in detecting stage. The results confirmed that the prepared colorimetric indicator could actually detect the integrity 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.

Alginate-based hydrogels embedded with ZnO nanoparticles as highly responsive colorimetric oxygen indicators

“…Their sensitivities are also very similar to those of previously reported film-based oxygen indicator systems. 18,19,21 Additionally, modification of the alginate matrix to prevent dye leaching and restriction of photocatalytic degradation of MB are essential to enhance the stability and O 2 sensing performance of hydrogel sensors. Further studies on the effects of humidity and temperature on the oxygen sensitivity, physical, mechanical properties of the hydrogel, and the gas selectivity are currently underway to apply these hydrogel sensors over a broad range of humidities as in realistic conditions, particularly in environmental gas sensing and MAP systems in the food and pharmaceutical industries.…”

“…Typically, colorimetric oxygen indicators consist of metal oxide nanoparticles such as TiO 2 , ZnO, and SnO 2 , which act as photocatalyst semiconductors; a redox indicator, usually methylene blue (MB); and a sacrificial electron donor (SED) such as glycerol to enhance the photocatalytic reaction. [18][19][20][21][22][23] These components are usually deposited onto a polymer support matrix to impede their molecular mobility, which may improve the decoloration and reversible stability of the sensing material. However, these polymer-based colorimetric oxygen indicators have several drawbacks.…”