Numerical heat transfer modelling for improving thermal protection of fish packaging

Thermal protection of fresh fish packaging can substantially reduce negative effects of poor temperature control in chill chains. The aim of the current study was to apply numerical heat transfer modelling to improve such packaging by redesigning an expanded polystyrene (EPS) fish box. By thickening the walls at the corners the insulation performance of the box was enhanced and to counterbalance the weight of the new box, the walls were made thinner further away from the corners. By this means, the reference box was optimised in a step-by-step procedure using a 'trial and error' method. A trial was conducted to compare the improved and the reference EPS boxes, using fresh fish products subjected to thermal loads likely to occur during air- and land based multimodal transport from a processor in North-Iceland to a wholesaler in Europe. The improved EPS box weighed around 11% less than the reference EPS box. The performance of the EPS boxes was evaluated by means of temperature monitoring, chemical- and microbial measurements and sensory evaluation. Finally, the shelf life of fish loins subjected to air transport simulation was compared to continuous containerised sea transport (around -1 °C). The improved EPS boxes provided significantly better thermal protection compared to the reference boxes. Sensory evaluation gave approximately 2-3 days longer freshness period and prolonged shelf life up to 1-2 days (8 days v. 6 - 7 days). Steady storage at -1 °C resulted in shelf life of 11-12 days. The conclusion is that the improved packaging can increase the value of fresh fish by a significant amount.