Electron spin resonance (ESR) spectroscopy has been used to assess the free radicals signal in different milk powders, buffalo's, cow's goat, camel, commercial full cream cow's milk powder, buffalo's butter milk and colostrum before and after γ-ray irradiation at does 1 and 2 KGy. Non-irradiated  milk samples exhibited weak signal intensity, depending on the type of milk. However, ESR signal intensity of all irradiated milk samples  gradually increased as the radiation dose increases from 1 to 2 KGy. The results showed that the radio-stability of milk powder depended on the original free radicals and radiation dose applied. Buffalo's butter milk and camel milk powders had the highest radio-stability, while buffalo's milk powder was the lowest. The results of this study recommended to use ESR as a new technique in evaluation quality control dairy products during processing and storage.