Comparison of the heating process and determination of the critical heating point was studied for homogeneous and nonhomogeneous products in 211 × 214 retortable plastic containers and metal cans. The fh, j, and Fo values for bentonite dispersions (4-10%), were significantly different at α= 0.05 for the metal cans versus the plastic containers with metal lid oriented up or down. The slowest heating point was mathematically determined and found to be influenced by the container material and the lid orientation for the plastic containers. Results indicated the design of thermal processes in plastic containers must take into account nonsymmetrical external heat transfer due to the presence of the metal lid.