AN INTERNATIONAL COLLABORATIVE BLIND TRIAL ON ELECTRON-SPIN-RESONANCE(ESR) IDENTIFICATION OF IRRADIATED CRUSTACEA

The results of an interlaboratory collaborative trial are presented wh ere 15 participating laboratories used the technique of ESR spectrosco py to detect three species of Crustacea irradiated in the frozen state and stored at -20 degrees C. Samples of Norway lobster (Nephrops norv egicus), pink shrimp (Pandalus montagui) and crevettes (Penaeus (Penae us) semisulcatus) were irradiated at dose levels of approximately 1, 3 and 5 kGy or left unirradiated. Each laboratory analysed nine samples of each species approximately 2 weeks following irradiation and the s ame number after storage for 2 months at -20 degrees C. In total, 270 samples were analysed for each of the three species of Crustacea. A 95 % correct identification rate was achieved for the crevette samples wh ere 256 of the 270 samples examined were correctly identified. Two-hun dred and twenty-six Norway lobster samples were correctly identified, giving a correct identification rate of 84%. The most disappointing re sults were associated with pink shrimp, where only 54% of the samples were correctly identified. Storage at -20 degrees C was not found to h ave a significant effect on detection of the irradiated samples.