Determination of Cold Spot Location for Conduction-Heated Canned Foods Using an Inverse Approach

Abstract

Cold spot location is a focal point in thermal process lethality calculations for conduction heated canned foods. An inverse heat conduction problem (IHCP) approach was used to model heat transfer for canned food with headspace using a one dimensional heat conduction model. Sequential function specification algorithm was used to solve for heat fluxes history at the can headspace side using known internal transient temperature measurements. The estimated heat fluxes were then used to solve the direct heat conduction problem for the temperature profiles in the axial direction including at the sensor position. Deviations between estimated temperatures and measured temperatures at the sensor position were calculated using root mean square error. From all the treatments used, a maximum error of 0.29 ^oC was obtained for the whole measurement period of the treatment which is well within thermocouple measurement error. The excellent agreement between the measured and calculated temperatures at the sensor position is an indication of an accurate estimation of heat fluxes and subsequent location of the cold spot. The results revealed that the cold spot is located at about 59 % of the model food height from the bottom of the can for the three levels of headspace investigated (10%, 14% and 20%). The result of this research provides a useful guide for accurate location of cold spot when collecting heat penetration data for conduction heated foods with headspace predominantly occupied by water vapor. This will aid in assuring the safety of canned foods based on accurate calculation of thermal process lethality.