Developing a microbial time-temperature indicator to monitor total volatile basic nitrogen change in chilled vacuum-packed grouper fillets

TTIs are smart labels designed to monitor food product temperature history that could be used to reflect quality throughout the cold chain. The objectives of this study are to develop a microbial TTI for vacuum-packed grouper fish fillets and then to test if TTI reflects microbiological and biochemical changes in fish fillets. Under constant and dynamic storage conditions, colour change can indicate three grades of fish freshness—very fresh, fresh, and spoiled—based on total volatile basic nitrogen (TVB-N) levels. Overall, similar activation energies observed in the time-temperature integrator (TTI) responses and the TVB-N of grouper fish fillets make the microbial TTI a good candidate for monitoring the freshness of fish products. Practical applications Temperature management in the cold chain has begun receiving more attention because unexpected temperature abuse can lead to food safety problems and a decline in consumer confidence. A precise and applicable method to indicate freshness degree for fish products is important when there is a broken cold chain. This work demonstrates that a microbial time-temperature indicator can be used to monitor the freshness of vacuum-packed fish fillets in cold chains based on TVB-N levels. This is particularly important for the fish when their microbiological and TVB-N analyses do not correlate well.