The activation energies of a whole and a skim milk powder were determined using an experimental technique devised from the transient model of self-heating proposed in a recent paper. Two activation energies were found for the whole milk powder which suggested that different reaction mechanisms took place at different temperature ranges. The first mechanism in the 130-145 degrees C temperature range had an activation energy of 203.2 kJ/mol. The second mechanism in the temperature range of 145-165 degrees C had an activation energy of 74.7 kJ/mol which was within the literature values for oxidation. The activation energy of skim milk powder was found to be 97.1 kJ/mol. Comparison of results from the current study was made with literature. The advantages of the new experimental method were discussed.