29D-14 |
An improved method to estimate temperatures during the cooling stage of sterilized cylindrical cans |
G. CHEN1, T. A. Haley2, C. M. Corvalan3, and O. H. Campanella1. (1) Dept. of Agricultural & Biological Engineering, Purdue Univ., 1146 Agricultural & Biological Engineering Bldg., West Lafayette, IN 47907-1146, (2) Food Safety & Regulatory Compliance, Bush Brothers & Co., 1016 E. Weisgarber Rd., Knoxville, TN 37909-2683, (3) Dept. of Food Science, Purdue Univ., 745 Agriculture Mall Dr., West Lafayette, IN 47907-2009 Numerical models have been used for some time to predict the evolution of temperature in the slowest heating and cooling zones of canned foods undergoing sterilization. Recently, numerical models based on spherical rather that cylindrical geometry have been presented, which is accomplished by finding the “apparent position” within the sphere that mimics the actual temperature profile of the canned food. The “apparent position” method has been found to provide a good agreement of temperature and accumulated lethality during the late heating stage of sterilization. However, there is a significant disagreement between the temperature predicted by this approach and the actual temperature at the initial stages of the cooling. Because nearly 20~40% of the accumulated lethality can occur during the cooling phase, these discrepancies may create problems in the calculation of overall lethality delivered by the entire process. Our objective was to develop a method to reduce the discrepancy between actual and model predicted temperatures during the cooling phase. A formula capable of calculating differences between the measured center temperature of cylindrical food containers and those predicted by the “apparent position” method was derived from the heat transfer equation. The time-temperature profile at the slowest heating and cooling zones in the container was calculated by the numerical solution of the heat transfer equations for a cylindrical geometry and was assumed as the “true” time-temperature profile. The calculated temperature differences were incorporated into the “apparent position” method during the cooling phase. An excellent agreement between “true” and predicted temperatures using the modified apparent position method was obtained for several process conditions. The modified apparent position method has significance for improving food quality and saving energy when it’s used for on-line correction of process deviations due to its accurate prediction of additional process time.
Session 29D, Food Engineering: Thermal processes
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