Selection of an optimum pH-indicator for developing lactic acid bacteria-based time–temperature integrators (TTI) Original Research Article

Among all time–temperature integrator (TTI) types, microbial-based TTIs prevail since their response is directly related to food spoilage. For the development of lactic acid bacteria-based TTIs, optimum pH-indicators were chosen as follows. Five kinds of potential pH-indicators and four species of lactic acid bacteria were used to create microbial-based TTIs. The qualifying standards for pH-indicator selection were defined as (1) the effect of microorganism inhibition, (2) the simplicity of mechanistic interpretation of the color development reaction, and (3) intensity of color development. In particular, the reaction of TTI color development could be enhanced from non zero-order to zero-order. Overall, the optimum pH-indicator for the microbial TTIs was bromocresol green, followed by bromocresol purple, bromophenol blue, chlorophenol red, and congo red, in descending rank order. In conclusion, the choice of pH-indicators was found to be selective to assure effective color development of TTI.