INVERSE SUPERPOSITION FOR CALCULATING FOOD PRODUCT TEMPERATURES DURING IN-CONTAINER THERMAL-PROCESSING

A procedure was developed for theoretical calculation of internal prod uct temperatures during in-container sterilization of foods. Experimen tal product temperatures were determined through traditional heat pene tration tests (processing in a retort with come-up time of increasing temperature and holding time at constant temperature). These were used to produce, through a proposed inverse superposition solution, a ''st andardized,'' normalized, dimensionless product temperature curve corr esponding to the response of product temperature to a constant retort temperature profile. This ''standardized'' curve was then used, throug h Duhamel's superposition theorem, to calculate product temperatures f or time-varying retort temperature profiles. Limitations associated wi th the application of Duhamel's theorem were also transferred to the p roposed methodology. Theoretical, for perfect mixing, and experimental , for conduction heating, data were used in example calculations.