DETERMINATION OF IRRADIATION MARKERS IN FOODS

Today’s food industry is faced with several important challenges, including food product deterioration and the constant increase of diseases related to the presence of pathogenic microorganisms in food products. Thus, adequate and effective food preservation strategies are even more important. Food irradiation is a technological process that can improve the microbiological quality of foodstuffs and extend the period in which it can be safely consumed. The radiation treatment, carried out under conditions of Good Manufacturing Practice, is considered as an effective, widely applicable food processing method judged to be safe on extensive available evidence. This technology can reduce the risk of food poisoning, control food spoilage and extend the shelf-life of foods without detriment to health and with minimal effect on nutritional or sensory quality. Due to its numerous positive effects, including those of a commercial nature, food irradiation has assumed a highly important role in the field of food preservation, and increasingly large numbers of foodstuffs are subjected to this treatment each year. For some time now, countries equipped with adequate food irradiation facilities have used this technology at well defined doses for the preservation of various foodstuffs. Because of the divergent opinions expressed by many consumers' organizations, the European Union has issued two directives (1999/2/EC and 1999/3/EC), which have been implemented in Italy by Legislative Decree No. 94 of 30 January 2001. Those directives aims at harmonizing the rules concerning the treatment and trade of irradiated foods in EU countries. With the open market, each country is obliged to accommodate the presence in its internal market of irradiated food commodities treated in other EU states or in extra-European countries. To further safeguard the consumer, the EU legislation provides for official annual checks at the product marketing stage, with the purpose of identifying improperly labeled or unauthorized products. Thus far, only limited food categories has been studied and subjected to interlaboratory validation by analytical detection methods for irradiated food identification. To meet the specific requirements of the laws and to increase acceptance of this type of food preservation technology, we have extended the field of application of both screening (PSL) and confirmatory (ESR, TL) physical methods to check compliance with labeling of irradiated foodstuffs. Therefore for consumer protection and information, following the invitation from the European Commission to improve and develop more reliable analytical standards, research work was focused on new applications of these physical methods. Relevant contributions have been made to the extension of the current field of application, with the development of promising analytical procedure able to estimate the actual dose administered to treated foods. The first goal was achieved investigating, even at low doses (0.1 kGy), the luminescence yield of oysters, considered a great delicacy in many parts of the world, and validating its identification with two physical techniques: PSL as screening method and TL as a confirmatory one. Besides oysters other seafood, including bivalve mollusks, i.e. brown Venus shells, clams, and mussels, all of which are widely consumed and likely to be treated with irradiation were studied with Electron Spin Resonance (ESR) spectroscopy. It is well known that irradiation by ionising radiation leads to the formation of many radical species which, if stable, could be detected in calcified tissue such as mollusks' shell. Identification of four irradiated species of bivalve mollusks, i.e. brown Venus shells (Callista chione), clams (Tapes semidecussatus), mussels (Mytilus galloprovincialis) and oysters (Ostrea edulis) was performed. ESR could definitely identify irradiated seashells due to the presence of long-lived free radicals, primarily CO2-, CO33-, SO2- and SO3- radical anions. The presence of other organic free radicals, believed to originate from conchiolin, a scleroprotein present in the shells, was also ascertained. The use of one of these radicals as a marker for irradiation of brown Venus shells and clams can be envisaged. In addition to detection procedures a reliable dosimetric protocol for the reconstruction of the administered dose in irradiated oysters was proposed. Finally the results of a study on official checks by an accredited laboratory aimed at both evaluating the performances of detection methods and the presence of irradiated food on the Italian market, are discussed. Non-compliances found are due to both incorrect labelling and irradiation in non approved facilities in extra European countries. In summary, two physical methods, electron spin resonance (ESR) spectroscopy and thermoluminescence (TL) were studied most extensively and applied on a wide range of foods with successful results, whereas limitations of current standards were also assessed. The development and application of analytical methods for correct identification of irradiated samples from non-irradiated samples, along with protocols for dose evaluation, have become important for several purposes: upholding regulatory controls, checking compliance against labeling requirements, facilitating international trade, and reinforcing consumer confidence. Therefore the research on new detection methods represents a key area and more studies in this field should be encouraged.