Growth of Listeria monocytogenes on fresh fish fillets stored in a Styrofoam-free eco-friendly cold pack container

Seafood is usually stored in a refrigerated or frozen form; however, conventional cold packs (CCPs) provide limited cooling and may damage products. This study evaluated the growth of Listeria monocytogenes on vacuum-packed frozen mackerel (Scomber japonicus) fillets stored in conventional container boxes (CCBs) with CCPs and in newly developed container boxes (NDCBs) with newly developed cold packs (NDCPs). Fillets were spot inoculated (2.0–2.5 log CFU/g) and stored for 72 h. In CCBs with CCPs, counts increased from 2.79–3.95 log CFU/g at 2–24 h, reaching 4.94–7.95 log CFU/g at 36–72 h. In NDCBs with NDCPs, counts rose to 2.64 log CFU/g at 24 h (1.02 log CFU/g increase), followed by 1.41–3.74 log CFU/g increase at 36–72 h. The difference between systems was ~1 log CFU/g at 48 h, increasing to 1.48 log CFU/g at 72 h. Growth data (24–72 h) were fitted to a first-order kinetic model, yielding D-values of 36.47 min (y = 0.0802x + 0.3127) for CCBs with CCPs and 41.70 min (y = 0.0565x + 0.1400) for NDCBs with NDCPs. These results evidenced that NDCBs with NDCPs reduced growth of L. monocytogenes by improving temperature control, demonstrating potential for safer seafood transport.