Detection of irradiated food by immunoassay – development and optimization of an ELISA for dihydrothymidine in irradiated prawns

This paper describes the development and use of a competitive enzyme -linked immunosorbent assay (ELISA) to detect prawns which have been irradiated. The ELISA utilizes a monoclonal antibody against a modified DNA base, dihydrothymidine. A comparison of extraction procedures demonstrated that DNA purification was not required and that crude prawn homogenate could be used in the ELISA. The ELISA was applied successfully to two prawn species, North Atlantic prawn (Pandalus borealis) and Tiger prawn (Penaeus monodon). The ELISA has a working range of 0.5-2 kGy with CVs typically below 10%. Storage of irradiated prawns for up to 12 months at -20 °C had no effect on ELISA performance. As most food contains DNA the assay has potential to be applied in a wide range of foodstuffs.