This European Standard specifies a method for the identification of irradiation treatment of food containing fat. It is based on the mass spectrometric (MS) detection of radiation-induced 2-alkylcyclobutanones after gas chromatographic (GC) separation [1] to [3]. The method has been successfully tested in interlaboratory trials on raw chicken, pork, liquid whole egg, salmon and Camembert [4] to [8]. Other studies demonstrate that the method is applicable to a wide range of foodstuffs [9] to [21].