ABSTRACTHeat penetration to cans of mussels in brine processed in an agitating retort was studied. The heating lag factor, j, and the time for the heating curve to traverse a log cycle, fh, as a function of the rotational speed, the headspace presence, and the come‐up time were determined. Heat penetration rates increased with end‐over‐end rotation at low rotational speeds. The presence of headspace produced significant improvements in heat penetration. Transient temperature profiles for this product were relatively short; therefore, improvements in heat penetration would only be significant when retort come‐up times ar