Heating rate index ( f h ), heating lag factor ( j h ) and accumulated lethality ( F o ) were determined in the plastic, 307 diameter retortable bowls during tests at 7 rotation speeds (0–30 rpm), and 3 radial positions ( R 1=0 mm, R 2=115 mm, R3=175 mm). End-over-end (EOE) rotation from 0 to 30 rpm significantly influenced all parameters, however, the effect of rotation speed was non-linear, such that higher rpm did not always improve heating rates. Substantial improvements in heating of the particle portion were seen at relatively low rpm. Although less important than rpm, even small (115 mm) radial position differences significantly altered F o in some cases ( p≤0.05). The effect of immobilization of food particles on the end of a thermocouple, investigated with Bacillus stearothermophilus ATCC 7953 spores sealed in differential scanning calorimetry (DSC) pans, revealed significantly lower lethality delivered to freely moving particles than to particles immobilized in the can center. A Hydrophobic Grid Membrane (HGM) technique allowed rapid and convenient enumeration of surviving spores. The bio-indicator approach provided a more conservative estimate of minimum lethality than rigid thermocouples positioned in the center of particles within cans. ©