The purpose of this work was to develop a means for determining product and process specific thermal kinetic parameters of constituents in foods that do not heat uniformly. The concept of the method of Paired Equivalent Isothermal Exposures (PEIE) was developed for such products. The ability of the PEIE to define Arrhenius parameters from simulated retort experiments was demonstrated. The PEIE was applied to survival data from retort experiments of canned pea puree inoculated with Bacillus stearothermophilus spores (NCA 1518). Mean activation energy and reaction rate constant (at 121.1°C) of the spores in retort processed canned pea puree were Ea= 250 (± 15) kJ/mol and k121.1°C= 0.26 (0.23 < k121.1°C <0.30) min−1, respectively.