Optimising the quality of safe food: Computational modelling of a continuous sterilisation process

Continuous food sterilisation processes require that a given level of sterility is reached for minimal quality loss. Current designs are empirically based on ideas developed on batch systems, for processing at high temperature for short time (HTST). A computational model for continuous flow sterilisation has been used to test these assumptions. A model system for a laminar flow in circular pipes with uniform wall temperatures has been developed; both Newtonian and non-Newtonian viscosity models, (including temperature dependence) have been used. Temperature and velocity profiles have been modelled using a validated computational fluid dynamics (CFD) package. Results from the simulations have been used together with conventional food processing sterility and quality kinetics, adapted to the continuous flow case. Data from the model were used to study the efficiency of a continuous sterilisation process. Results have shown that the conservative approach used in the food industry can lead to significant overprocessing and thus unnecessary deterioration of the overall product quality. The conventional HTST assumption fails under some circumstances, for example when the fluid layer near the wall is overprocessed.