Kinetics of Quality Changes of Pangasius Fillets at Stable and Dynamic Temperatures, Simulating Downstream Cold Chain Conditions

This study was about the quality changes of Pangasius fillets during storage under simulated temperature conditions of downstream cold chain. Sensory, chemical, and microbiological analyses were conducted over storage time and bacterial growth was modelled. Sensory quality index (QI), at five stable (1, 4, 9, 15, and 19 +/- 1 degrees C) and three dynamic temperatures, progressed faster at higher temperatures, especially with sooner temperature abuses. Total volatile basic nitrogen remained under the acceptable limit throughout all the storage conditions. Total viable psychrotrophic counts (TVC) were around 5.68 +/- 0.24 log CFU g(-1) at the beginning and exceeded the limit of 6 log CFU g(-1) after 216, 96, 36, 16, and 7 h at 1, 4, 9, 15, and 19 +/- 1 degrees C, respectively. Meanwhile, Pseudomonas counts started at 3.81 +/- 0.53 log CFU g(-1) and reached 4.60-6.36 log CFU g(-1) by the time of TVC rejection. Since lower shelf lives were given by TVC rather than QI, it should be appropriate to base the product shelf life on the TVC acceptable limit. Kinetics models based on the Baranyi and Roberts and square root models, developed for TVC and Pseudomonas spp., gave acceptable bacterial estimations at dynamic temperatures, with over 80% of observed counts within the acceptable simulation zone, revealing promising model applicability as a supporting tool for cold chain management. However, further improvement and validation of the models are needed.