Cooking systems producing complete, or ingredients for, chilled meals are designed to achieve temperatures of 70 degrees C for 2 min in the centre of the food, which should cause a 10(6)-fold destruction of Listeria monocytogenes. However, spore-forming micro-organisms will survive this process and multiply if the food is not rapidly reduced to a temperature below 10 degrees C. Experimental investigations have been carried out to study the cooling of different thicknesses of cooked solid-liquid mixtures under a range of immersion chilling conditions. An iterative computer model of the process has been developed and used to extend these data to cover alternative processing conditions and a range of cooked meals. If surface freezing was to be avoided then it was found that only the shallowest (10 mm) tray could be chilled within the limits of the most severe European Guidelines. However, the model also predicted that the 40 mm trays of food would cool within the limits of the Guidelines if oriented differently.