Time-temperature indicators based on Lipase@Cu3(PO4)2 hybrid nanoflowers

The application of enzyme-inorganic hybrid nanoflowers in time-temperature indicators (TTIs) was studied for the first time. Lipase@Cu 3 (PO 4 ) 2 hybrid nanoflowers were prepared by the interaction between lipase and copper ions. Compared with free lipase, the activity of lipase in the nanoflowers was increased by 137%, and the storage stability was also improved significantly. Based on the enzymatic reaction between lipase and glycerol triacetate, six TTI prototypes with different concentrations of lipase@Cu 3 (PO 4 ) 2 hybrid nanoflowers were investigated. The color of the six TTIs changed from purple to yellow, and finally to green, and the activation energies were 46.86 kJ/mol, 51.17 kJ/mol, 54.99 kJ/mol, 60.00 kJ/mol, 62.17 kJ/mol, and 65.63 kJ/mol, respectively. The shelf life of TTIs can be determined by changing the ratio of lipase@Cu 3 (PO 4 ) 2 hybrid nanoflowers to glycerol triacetate, therefore the TTIs can be easily applied to real-time safety evaluation of many perishable foods.