An Alternative Procedure for ESR Identification of Irradiated Chicken Drumsticks F. BORDI*, P. FATI-IBENE”, S. ONORI”, M. PANTALONI” *Dipartimento di Medicina Interna Sezione di Fisica Medica II Universita di Roma, Via O.Raimondo, I-00173 Rome, Italy “Istituto Superiore di Sanita and Istituto Nazionale di Fisica Nucleare Sezione Sanita, Viale Regina Elena 299, I-00161, Rome, Italy The ESR spectroscopy is, at present, the most established technique for quantitative analysis of irradiated chicken bone using the additive dose method. In this paper we tried a different approach to the problem analyzing the ESR behavior of a batch of chicken bone samples coming randomly from the market. Using a suitable and standardized sample preparation technique and sample positioning in the microwave cavity, we obtained a coefficient of variation of about 30% for the batch response. The calibration curve, obtained using the batch behavior up to 10 kGy, was used for a quantitative test on unknown samples. KEYWORDS: Food irradiation, ESR. INTRODUCTION The irradiation of food is receiving a great world-wide interest as a suitable technique for reducing losses and improving the safety of the food itself. As a consequence, many countries started research programs aimed at developing identification methods suitable to check compliance with national regulations. Among the proposed physical methods, the electron spin resonance (ESR) technique seems to be, at present, the most established method for the analysis of irradiated food containing bones or calcified cuticle. A recent intercomparison on ESR identification of irradiated food organized by the Community Bureau of Reference (BCR), Commission of the European Communities (Raffi, 1991), shows that the method is ready for qualitative (the product has been irradiated or not) routine control of meat bones. Nevertheless, in the framework of the same BCR program, it was concluded that the use of the ESR technique for the quantitative analysis (evaluation of the given dose) of poultry bones still deserves attention. In fact, strong deviations in the answers of the participant laboratories came out for samples irradiated at the same dose as well as between the nominal and the evaluated dose values. Moreover the dose additive method, which is the only one proposed up to now and which was used in the BCR program for the quantitative analysis, suffers from the basic limitation to require, at the same time and in the same evaluating laboratory, both an ESR machine and a suitable ionizing radiation source. It is then clear that additional efforts are needed to find simpler procedures and to obtain more accurate results. For instance, among the points still deserving attention, the sample preparation and positioning inside the microwave cavity and the reproducibility of the additive dose values should be quoted. The aim of the present work was: i) to increase the reproducibility of the technique by using a suitable and standardized procedure for sample preparation and read-out, ii) to test the possibility of using a calibration curve, obtained from a statistic population, as an alternative procedure to the dose additive method for the quantitative evaluation of unknown samples. This last possibility lies on the 443