APPLICATION OF DIFFERENT TECHNIQUES TO IDENTIFY THE EFFECTS OF IRRADIATION ON BRAZILIAN BEANS AFTER 6 MONTHS STORAGE

Four different techniques to detect the effect of irradiation in beans were investigated. Two types of Brazilian beans, Phaseolus vulgaris L ., var. carioca and Vigna unguiculata (L.) Walp, var. macacar, were ir radiated using a Co-60 source With doses ranging from 0, 1.0 to 10.0 k Gy. After 6 months storage at ambient temperature the detection tests were carried out. Firstly, germination tests showed markedly reduced r oot growth and almost totally retarded shoot elongation of irradiated beans as compared to non-irradiated beans. Secondly, DNA fragmentation was studied using a microgel electrophoresis. Irradiated cells produc ed typical comets with DNA fragments migrating towards the anode. DNA of non-irradiated cells exhibited a limited migration. Thirdly, electr on spin resonance for detection of cellulose radicals was tested, sinc e it was expected that these free radicals are quite stable in solid a nd dry foods. However, only in beans irradiated with 10 kGy a small si gnal could be detected. Fourtly, thermoluminescence, a method to analy ze mineral debris adhering to food, turned out to be a good choice to detect irradiation effects in beans, even after 6 months of storage. T he results indicate that three of these four techniques proposed, can be used to detect the effect of irradiation in these two varieties of Brazilian beans at a dose level useful for insect disinfestation(1 kGy ).