Identification of irradiated foods

A reliable method is needed to determine if foods have been irradiated and are in compliance with respect to the allowable absorbed radiation dose. Several approaches for the identification of irradiated foods are under development worldwide. These include measurement of o-tyrosine, radiolytically generated hydrocarbons from lipids and chemiluminescence or thermoluminescence, and the use of electron spin resonance (ESR) to measure free radicals trapped in calcified tissues. This paper describes the efforts being undertaken at the FDA to develop analytical procedures to monitor and identify foods that have been treated with ionizing radiation. In particular, it focuses on the use of an ESR approach to measure radiation-induced free radicals trapped in calcified tissues and the use of a capillary gas chromatography (GC)-based procedure to determine radiolytically generated hydrocarbons formed by the radiolysis of lipids in various foods.