Computer Simulation of On-Line Control of Thermal Sterilization of Canned Foods Subjected to Arbitrary Retort Temperature Deviations

A computer control logic algorithm has been developed to compensate for the effects of arbitrary retort temperature deviations on lethality. The algorithm is based on calculating the can center temperature for any retort temperature profiles using an alternating direction implicit finite difference method. Lethal rate and corresponding accumulated lethality were calculated during the simulation process. Five types of process deviations were investigated including one with multiple deviations. All the deviations investigated resulted in serious under processing with relative errors in sterilization value ranges from 16.9 % to 43.2 %. A correction measure for process with retort temperature deviations based on targeting the lethal rate of the standard process at the end of the heating phase was proposed. The implementation of this measure resulted in successful correction for all the deviations investigated with a maximum relative error in sterilization value of 9.5 % on the over processing side. This work indicates that the current control algorithm could be incorporated in HACCP guideline, as an online corrective measure for retort temperature deviations during thermal sterilization process.