Modelling and simulation of pasteurization and staling effects during tunnel pasteurization of bottled beer

Convective transport of micro-organisms and staling effects are not normally considered during the design of a tunnel pasteurization plant. However, if increasing demands on product quality are to be met, those effects have to be taken into account. This paper describes a model for the unsteady convective heat transfer inside a bottle, taking into account the influence of the convective flow on pasteurization and staling effects. Simulation results indicate that the model gives a good representation of experimental results, both of laboratory and process data. Simulation studies show that the traditional procedure for determining pasteurization units (PU) can overestimate the actual effect considerably if the reference point is not chosen accurately with reference to the bottle size and shape. Furthermore, it is suggested that a unit definition for the pasteurization induced staling effect should be developed comparable to the PU definition.