Effect of γ-irradiation on the occurrence of pathogenic microorganisms and nutritive value of four principal cereal grains

The effects of 60Co γ-photon-irradiation on the natural occurrence of pathogenic microorganisms in four principal cereal grains and on amino acids and vitamins in these cereals were investigated. The total numbers of aerobic bacteria were reduced by three logarithmic decades when grains were given a dose of 10 kGy. Coliforms and “coagulase- positive” staphylococci were inhibited by a dose of 1 kGy, whereas fungi were inhibited by a dose of 5 kGy. The 15 kGy dose eliminated viable microorganisms in cereal grains, and about 10–30 colony-forming units of Clostridium sp. per gram of grain survived after this dose. The dose of 10 kGy did not cause any measurable destruction of total amino acids. Thiamin was reduced by 22–33% and riboflavin by 10–16% after a dose of 10 kGy. Irradiation did not increase the acid values significantly, but did increase the peroxide values, which was not accompanied by the off-odors of cereals. We conclude that the overall dose of 10 kGy is very effective for microbial decontamination of cereal grains, and does not adversely affect the nutritional quality of cereal grains.