This report presents the estimation of the activation energy (E) values from the thermoluminescence (TL) glow curves showed by the whole glow peak (WGP) method that allows us to distinguish between irradiated and non-irradiated chilli powder samples. The E values of non-irradiated samples maintain 0.65 eV whereas irradiated ones reach 0.84 eV or upper. Furthermore, the E values are obtained from the result of comparison between the chilli powder irradiated with different doses (2, 4, 6 and 8 kGy) stored for 30 days and other unknown chilli powder samples in Vietnam.