Detection of Irradiated Ingredients Included in Low Quantity in Non-irradiated Food Matrix. 2. ESR Analysis of Mechanically Recovered Poultry Meat and TL Analysis of Spices ERIC MARCHIONI,* ,² PE Ä TER HORVATOVICH, ² HELE Å NE CHARON, ² AND FLORENT KUNTZ § Laboratoire de Chimie Analytique et Sciences de l’Aliment (UMR 7512), Faculte ´ de Pharmacie, 74 route du Rhin, F-67400 Illkirch, France, and Ae ´rial, Parc d’innovation, rue Laurent Fries, B.P. 40443, F-67412 Illkirch Cedex, France Protocols EN 1786 and EN 1788 for the detection of irradiated food by electron spin resonance spectroscopy (ESR) and thermoluminescence (TL) were not conceived for the detection of irradiated ingredients included in low concentration in nonirradiated food. An enzymatic hydrolysis method, realized at 55 °C, has been developed for the extraction of silicate minerals and bone fragments. When followed by a purification of the extracts by an aqueous solution of sodium polytungstate, this method made it possible to detect very low inclusions of irradiated spices (0.05%, wt/wt by TL) included in various meals (cheeses and precooked meals). Even for food containing together two ingredients (spices and mechanically recovered meat), it was possible to detect and identify them simultaneously. KEYWORDS: Food irradiation; detection of irradiated foods; ingredient; spices; mechanically recovered meat; thermoluminescence; ESR INTRODUCTION European Directive L66/16 (1) forces the food industry of all member states of the European Union to indicate on the label if one of the food ingredients was irradiated, whatever the inclusion rate might be. The electron spin resonance (ESR) detection of irradiated foods, when sold as items, and thus the control of their labeling do not present any major analytical problem because 10 standardized protocols were published by CEN. The situation is not the same when the detection of an irradiated ingredient included in low amounts in a non-irradiated food is to be considered. Spices, aromatic herbs, and mechanically recovered poultry meat (MRM) are currently the foods most frequently subjected to irradiation. These foods are primarily used as ingredients by the food-processing industry. The best dedicated reference protocol (2) for the detection of irradiated herbs and spices [analysis of excited electrons trapped in silicates by thermo- luminescence (TL) after ultrasound treatment of the samples and decantation of silicates in an aqueous solution of sodium polytungstate] and meats (analysis of induced radicals in bones by ESR spectroscopy after manual recovery and drying) (3) is irrelevant when silicates and small bone fragments are included in low amounts in a lipidoproteic complex matrix (cheeses, quenelles, etc). It is actually essential to remove the food matrix as much as possible before analysis of silicates by TL and of bone fragments by ESR spectrometry. Regarding the detection of irradiated bone fragments, Gray and Stevenson recommended an alkaline hydrolysis of food matrix by alcoholic boiling KOH (4) and Stevenson et al. an enzymatic hydrolysis by Alcalase (5). More recently, Marchioni et al. (6) proposed to perform the purification step with an aqueous solution of sodium polytungstate to get higher purity bone fragments and better ESR spectra. These authors achieved the detection of very low amounts (0.5%, wt/wt) of irradiated MRM included in industrial foods. However, the method was proposed for the detection of only irradiated MRM or fish bones in food and not for the detection of irradiated spices. Regarding the detection of irradiated spices (2), Carmichael et al. (7) proposed an acidic hydrolysis of the shellfish matrix to extract the silicate minerals. It might be possible to use this hydrolysis method for the TL detection of irradiated spices included in non-irradiated food. However, this protocol, proposed for the detection of only irradiated crustaceans and shellfishes, was never proved to be efficient for such a use. Furthermore, the acid hydrolysis (6 M HCl, 110 °C, 2 h) would certainly alter the integrity of the bone fragments, and this method cannot thus be used for the ESR detection of irradiated MRM or fishes in food. Some previous works (5, 8) have demonstrated the powerful hydrolytic capacities of Alcalase, which is an industrial protein enzyme reaching its maximum effectiveness under soft condi- * Author to whom correspondence should be addressed [telephone 33 (0)3 90.24.43.26; fax 33 (0)3 90.24.43.25; e-mail eric.marchioni@ pharma.u-strasbg.fr]. ² Laboratoire de Chimie Analytique et Sciences de l’Aliment (UMR 7512). § Ae ´rial. 3774 J. Agric. Food Chem. 2005, 53, 3774-3778 10.1021/jf0481002 CCC: $30.25 © 2005 American Chemical Society Published on Web 04/16/2005