Effect of Ionizing y-Radiation on Thermoluminescence and Electron Spin Rosonance Intensities in Milk Protein Concentrate Powders

Milk protein concentrate powder has found a wide application as a food ingredient. We investigated the effects of ionizing ')'-radiation at doses ranging from 2 to 20 kGy on electron spi n resonance and the rmoluminescence intensities in samples of milk protein concentrate powder with varying protein contents (36-73 %wt), containing addltional Fe ++ ions (12-910 ppm) and stored under different condit ions. Electron spin resonance and thermoluminescence intensities increased unambiguously with absorbed -ydose. Added Fe ++ ions showed a quenching effect as measured by both methods. Storage conditions affected strongly the decay of electron spin resonance signal intensity . Lineshape analysis of thermoluminescence curves indicated the existence of two trap levels of different depths which re flected two different recomb ina tion processes. Fe++ ions bound to states corresponding to trap levels of shal low depth, thus inactivating th eir effect. Electron spin resonance and thermoluminescence meth ods were equally suitable for the detect ion of the degree of irradiation but their applicability depended on storage con dition s. A close corre lation was found between these two methods (r ~ 0.973). In itial paper received July 9, 1991 Manuscript received April 10, 1992 Direct inquiries to J. Kispeter Telephone number: 36-62-23 I 88 Fax number: 36-62-25977