DIN EN 1787:2022-08: Foodstuff - Detection of irradiated foodstuff containing cellulose by ESR spectroscopy; German version EN 1787:2022

This document specifies a method for the detection of cellulose-containing foods treated with ionising radiation. In this method, the ESR (electron spin resonance), also known as EPR (electron paramagnetic resonance) spectrum of the food is analysed. Interlaboratory tests were successfully carried out with pistachio shells, paprika powder and fresh strawberries. However, it has been shown that chemical bleaching of nuts in shells can lead to comparable signals. Further information on the limitations of the method can be found in the document. ESR spectroscopy is used to detect paramagnetic centres (for example radicals). These are either due to irradiation or to the presence of other compounds. A strong external magnetic field creates a difference between the energy levels of the electron spins ms = +${}^1$/${}_2$ and ms = -${}^1$/${}_2$, which leads to resonance absorption of an irradiated microwave beam in the spectrometer. ESR spectra are usually presented as the first derivative of the absorption as a function of the applied magnetic field. The values of the magnetic field and the microwave frequency depend on the experimental setup (sample size and sample holder), while their ratio (i.e. the g-value) is an intrinsic characteristic of the paramagnetic centre and its local coordination. Exposure to ionising radiation generates specific radicals that can be detected mainly in hard and dry components of the food. The intensity of the signal obtained increases with the concentration of the paramagnetic compounds and therefore with the dose applied. This document (EN 1787:2022) has been prepared by Technical Committee CEN/TC 275 "Food analysis - Horizontal methods", the secretariat of which is held by DIN (Germany). The responsible German standardisation body is the working committee NA 057-01-02 AA "Irradiated foodstuffs" in the DIN Standards Committee Food and Agricultural Products (NAL). This document supersedes DIN EN 1787:2000-07. Compared to DIN EN 1787:2000-07, the following changes have been made: a) the scope has been extended to include the information that chemical bleaching of nuts in shells can lead to comparable signals; b) the section "Terms" has been added; c) the scientific language used in the section "Principle" has been clarified; d) 4. 1, 4.2 and 4.7 have been updated and a footnote on g-value calculation has been added; e) the section "Implementation" has been scientifically clarified, the normative aspects (i.e. (i.e. the rules set out therein) have been modified to formulate the rules more as an example/suggestion and it has been aligned with EN 13708; f) the sub-section "General" has been added to the sub-section "Sample preparation"; g) the section "Evaluation" has been extended in alignment with EN 13708 by two sub-sections, 7. 1 "G-value calculation" and 7.2 "Identification of irradiated samples", with the previous content of the subsection being included in 7.2 and "6.0 mT" being clarified to "6.05 mT ± 0.05 mT"; h) the section "Limits of the method" has been extended; i) Figure A.5 and Figure A.7 of irradiated but bleached nut shells of hazelnuts and walnuts and Figure A.6 and Figure A.8 of irradiated (non-bleached) nut shells of hazelnuts and walnuts were added; j) Annex B was extended to include the matrix hazelnuts; k) the references were updated and extended to include entries [23], [24] and [25]. l) complete editorial revision and adaptation to the currently valid design rules.