A novel self-powered time-temperature integrator (TTI) using modified biofuel cell for food quality monitoring

• A novel self-powered time-temperature integrator (TTI).
• The novel TTI outputs an electrical signal instead of colour change.
• The novel TTI was created by modifying a biofuel cell.
• The novel TTI performance was validated in a case study with milk deterioration.

A self-powered time-temperature integrator (TTI) was developed by modifying a biofuel cell and characterised in terms of kinetics and temperature dependency. The TTI was composed of two immobilised enzyme electrodes, (+) and (−), and a cavity containing substrates. The enzymes (laccase and glucose oxidase), mediators (methylene blue, 8-hydroxyquinoline-5-sulfonic acid hydrate, ferrocenium hexafluorophosphate, 4,4-sulfonydiphnol) and stabilisers (pyrrole) were immobilised on a glassy carbon electrode by electrodeposition by applying a square wave (10 s at 4 V then 3 s at 0.5 V) for 180 cycles. The primarily measured output voltage, which corresponds to a rate of food quality change, was mathematically converted to a secondary variable, its integral value, representing the food quality level. The temperature dependency of the self-powered TTI was modified by using sodium azide, and the shelf-life of TTI could be adjusted to match that of the food product by changing glucose concentrations. The optimum Arrhenius activation energy was found to be 78.22 kJ/mol with a sodium azide concentration of 0.02 M and the glucose concentration at the maximum (5.05 M), it used continuously for 7 days at 25 °C. Through a case study with milk, the novel TTI was found to accurately detect milk quality changes. The self-powered TTI can be utilised as an intelligent versatile sensor in the food distribution system with an appropriate IT platform. In particular, if the TTI is incorporated with RFID tag, we will see a new generation of smart RFID tag for intelligent food packaging.