Detection of radiation treatment of meat by novel techniques of DNA comet assay

Treatment of food to ionizing radiation is being progressively used in many countries to inactivate food pathogens, to eradicate pests and to extend shelf life; thereby contributing to safer and more plentiful food supply. Food control agencies throughout the world need some reliable, simple and rapid methods for detection of irradiated foods to ensure free choice of consumer and to enforce labeling. The DNA comet assay offers great potential as a rapid tool to screen irradiated and unirradiated samples of several kinds of foods. In the present study, frozen beef has been investigated for detection of irradiation treatment. The samples were subjected to radiation doses of 0,4,5 and 7.0 kGy and were stored in freezer before analysis. The cells were extracted into cold PBS solutions, embedded into the agarose gel on microscope slides, lysed and electrophoressed at a voltage of 2v/cm for 2 min. The fragmented DNA as a result of irradiation treatment was stretched in the gel producing the dose dependent comets. These comets were visible using a simple transmission microscope after silver staining. The controlled and irradiated samples of meat were clearly distinguishable on the basis of the stained patterns of DNA in form of round or conical intact cells for unirradiated samples or in form of comets for irradiated samples. It is therefore, concluded that 'DNA Comet Assay' offers a potential to screen unirradiated and irradiated meat samples. (author)