Optimum on-line correction of process deviations in batch retorts through simulation

This paper describes broader applications of computer-based batch retort control systems that make use of mathematical models to accomplishing on-line correction of unexpected process deviations in thermal processing of low-acid canned foods. Current systems over extend process time with costly consequences to product quality and retort operating schedules in cook room operations. These problems are addressed by describing novel control strategies that also treat the retort temperature as a control variable, rather than just process time alone. On-line correction is accomplished by choosing an optimum higher constant retort temperature for the remainder of the process that will deliver the specified target lethality within the original process time remaining. The paper also describes on-line correction of process deviations occurring during a pre-programmed variable or dynamic retort temperature process that might be chosen to maximize nutrient retention in a conduction-heated food. In this situation, an optimum combination of retort temperature and process time is chosen for the remainder of the process that will deliver the maximum possible nutrient retention without compromising the specified final target lethality. Examples are given for the case of solid product undergoing a conduction-heating process in different shaped containers (cylindrical can and retort pouch), as well as liquid product undergoing forced convection heating in cylindrical cans under mechanical agitation.