Numerical Investigation on the Effect of Uncertainty in Thermal Diffusivity on Thermal Process Lethality of Canned Foods

Abstract

The effect of uncertainty in thermal diffusivity on thermal process lethality was investigated for a model food of 8 percent canned bentonite suspension in two different can sizes. A developed computer program that account for can headspace thermal resistance and finite thermal resistance during cooling was used in this investigation. Six levels of errors in thermal diffusivity (±2%, ±5% and ±10%) were used to generate computer simulation time-temperature data at the geometric centre for both cans. The calculated lethality values from the time-temperature data when errors were imposed on thermal diffusivity were compared to that of the standard process. The results of the investigation revealed that error in thermal diffusivity of (-2%, -5% and -10%) resulted in under-processing, while error of (+2%, +5% and +10%) resulted in over processing. The magnitude of error in lethality from +10 percent errors in thermal diffusivity is substantial for both short can and long can investigated reaching a value of 35.4 percent for the short can and 44.5 percent for the tall can. The results from this study clearly indicate that thermal diffusivity could be a critical control point in thermal processing of foods which requires corrective action if there is deviation from the true value.