Thaumatin, egg white and soybean protein were selected as samples of proteinous food additives, and changes in the intensity of signals appearing in them after they had been irradiated with electron beams were measured by ESR. It was found by such measurement that the positions of signals of thaumatin and soy proteins are nearly the same. Changes in the intensity of radicals in thaumatin calculated on the basis of the coefficients of the respective approximations obtained by using thaumatin which had been irradiated and then stored at 4°C, 25°C, 37°C and 60°C showed that there is a temperature range to determine the remaining of such radicals (inner: 19.7°C, outer: 15.23°C) and that such radicals tend to decrease straight line-wise. It was confirmed that the intensity of signals in the protein powder such thaumatin and soy protein would not be affected at the storage condition below 15°C.