Kinetic modeling and characterization of a diffusion-based time temperature indicator (TTI) for monitoring microbial quality of non pasteurized angelica juice

Time-temperature-indicator, or integrator (TIT), can be used for visual display of food product safety information for consumers. A prototype isopropyl palmitate (IPP) diffusion-based TTI system was characterized and evaluated for monitoring microbial quality of non-pasteurized angelica (NPA) juice based on temperature abuse. Diffusion of IPP in the TTI system was measured at various iso-thermal and dynamic temperatures and a mathematical model based on relationships between diffusion and time temperature was established. Predicted results from the established model were in good agreement with experimental results. Total aerobe counts in NPA juice reached a critical level of 6 log CFU/mL from an initial load of 3.7 log CFU/mL after 36.6 h and 12.5 h of storage at 15 degrees C and 25 degrees C, respectively. IPP diffusion distances were 9.7 mm and 7.2 mm at 15 degrees C and 25 degrees C, respectively. IPP diffusion of 7.0 mm in the TTI system was considered to be a threshold point for bacterial quality of NPA juice. However, the proposed TTI was only verified for indicating temperature abuse above 13.5 degrees C. The TTI system characterized in this study showed potential for monitoring the microbial quality of perishable food products during distribution and storage. (C) 2015 Elsevier Ltd. All rights reserved.