Temperature Distribution at the Surface of Cans in an Industrial Scale Static Retort during Saturated Steam Sterilization

Abstract

A temperature distribution study was carried out in an industrial scale static retort during steam sterilization of cans packed with tuna fish. Interest was focused on the surface temperature of conduction heating foods in cylindrical cans placed at various positions in the retort. Since saturated steam release latent heat at a temperature which is governed by pressure and has a large heat transfer coefficient, temperature at the outside surfaces of cans to which it is in contact with might be regarded as the same from one can to another. On the otherhand some process engineers may have experienced that there is a non-uniform temperature distribution in the retort during steam sterilization. Unfortunately, however, no data have been published in literature. In this paper, temperature on the trunk surface of 23 cans selected from a pack of 570 cans loaded into a commercial retort was observed during steam sterilization at 113°C for 80 min including come-up time. From the monitored data, it was observed that, considerable deviations in temperature took place during the come-up period (9 min) but it converged to a constant thereafter. A maximum of 40°C difference in temperature and the delay of 3 min in temperature rise was observed during the come-up period. This deviation at the early stages of heating was found to affect 30% change in sterilization value even though the come-up period was so short less then 11% of the total heating time.