A solid-state time-temperature indicator used in chilled fresh pork monitoring

A solid-state enzymatic time-temperature indicator (TTI) was developed in this paper. Glucoamylase microcapsules, emulsifier, and substrate solution were mixed uniformly, then the mixture was coated on a paper and could be activated by an agar cover. Both single factors and orthogonal experiments were conducted to obtain qualified formulations whose endpoints ranged from 5 to 6 days with storage temperature maintained at 4 degrees C. The Arrhenius activation energy (E-A) of obtained TTIs was also calculated at 107, 97.5, 88.0, 107, 98.5, 87.7, and 89.7 kJ/mol. For the application of TTIs to chilled fresh pork monitoring, both the spoilage mechanism and kinetic properties of pork were studied and an E-A value of 64.7 kJ/mol was obtained. After isothermal verification, a qualified TTI formulation was obtained, of which the mass of glucoamylase microcapsules was 0.02 g, the mass of amylose was 5 g, the concentration of iodine solution was 0.1 M, and the thickness of agar cover was 2 mm. The time-temperature history of chilled fresh pork can be indicated by the colour response of the TTI.