🍎 Detection of foods containing crystalline sugars that have been treated with ionizing radiation — analysis of the electron spin resonance (ESR, also EPR) spectrum of the sample: radiation produces radicals in solid and dry parts of the food, and a multicomponent ESR spectrum proves prior irradiation (absence of the spectrum does not prove that the sample was not irradiated); validated in interlaboratory studies on dried figs, mangoes, papayas and raisins (about 0.5–7 kGy); condition — sufficient crystalline sugar, dried fruits must not be rehydrated; PN-EN 13708:2022-08

Food chemistry PN-EN 13708

Overview

WHAT THE STANDARD COVERS. We read the text of EN 13708:2001 (English version) made available by the European Commission on its food irradiation pages: scope, principle, limitations and validation with two tables of interlaboratory results — 2 pages. The current PN-EN 13708:2022-08 introduces EN 13708:2022 (PKN search); we did not read the 2022 text, so we do not give differences between editions. The procedure (apparatus, sample preparation, spectrometer parameters), evaluation of spectra and the annex with figures of spectra are not in the text read.

ACCORDING TO THE TEXT OF EN 13708:2001. Scope (1): a method for detecting foods containing crystalline sugars that have been treated with ionizing radiation, by analysing the electron spin resonance (ESR) spectrum, also called the electron paramagnetic resonance (EPR) spectrum; interlaboratory studies were successfully carried out on dried figs, dried mangoes, dried papayas and raisins. Principle (2): ESR spectroscopy detects paramagnetic centres (e.g. radicals) — due to irradiation or to other compounds present; an intense external magnetic field produces a difference between the energy levels of the electron spins ms = +½ and ms = −½, leading to resonance absorption of an applied microwave beam in the spectrometer; ESR spectra are conventionally displayed as the first derivative of the absorption with respect to the magnetic field; the field and microwave frequency depend on the experimental arrangement (sample size, holder), while their ratio (g value) is a characteristic of the paramagnetic centre and its surroundings; radiation produces radicals detectable in solid and dry parts of the food, and the signal intensity increases with the concentration of paramagnetic compounds and thus with the dose. Limitations (3): the general formation processes of radiation-induced radicals are known, but the radicals responsible for individual signals have not been identified; the association between irradiation and the signals described in the standard has been demonstrated in many studies; multicomponent ESR spectra prove prior irradiation, but absence of the specific spectrum does not prove that the sample was not irradiated; different mono- or disaccharides may dominate in the sample, giving different spectra after irradiation; if no sugar crystals are present, irradiation will not produce specific signals; detection of irradiated dried figs, mangoes, papayas and raisins has been validated; the lower limit of detection depends mainly on the crystallinity of the sugar in the sample; storage for at least several months does not significantly influence detection; applicability depends on sufficient crystalline sugar at all stages between irradiation and testing; sensitivity to radiation can be confirmed where necessary by irradiating a portion of the sample and retesting; dried fruits must not have been rehydrated before testing. Validation (4): the standard is based on two interlaboratory tests; in the BCR (Community Bureau of Reference) test 21 laboratories identified coded samples of dried papayas and raisins — unirradiated or irradiated to about 0.5, 1, 2, 4 or 7 kGy (Table 1): raisins — 126 samples, 7 false negatives (all from the 19 samples irradiated at 0.5 kGy), 1 false positive; dried papayas — 126 samples, 2 false negatives (from the 21 samples at 0.5 kGy), 0 false positives; in the test of the German Federal Institute for Health Protection and Veterinary Medicine (BgVV) 17 laboratories identified samples of dried mangoes and figs unirradiated or irradiated to about 1, 3 or 5 kGy (Table 2): mangoes — 184 samples, 0 false negatives and 0 false positives; figs — 184 samples, 2 false negatives, 0 false positives.

STATUS (as of 03.10.2026). In the PKN search engine (query "PN-EN 13708", 03.10.2026) PN-EN 13708:2022-08 appears in Polish and English versions, "Introduces: EN 13708:2022 [IDT]", without a withdrawal note; PN-EN 13708:2003 (Polish version, introduced EN 13708:2001) — "Withdrawn and replaced by PN-EN 13708:2022-08 - English version"; PN-EN 13708:2002 (English version) — withdrawn and replaced by PN-EN 13708:2003.

HOW MANY LABORATORIES AND IN WHAT FORM (copy of the accreditation scope database, load up to 17.09.2026, read 03.10.2026). The number 13708 appears in 2 records at 2 laboratories: AB 262 and AB 537. In the current PCA documents (read 03.10.2026; AB 537 issue no. 28 of 07.08.2026, AB 262 issue no. 18 of 25.09.2026) the number appears at the same 2 laboratories; in each document the number of page markers equals the number of PDF pages, without duplicates; searching all PCA documents downloaded from the BIP on 03.10.2026 found no laboratories outside the database copy. Form at both: "PN-EN 13708:2022-08". None of these items is suspended. The "Laboratories" tab (query "PN-EN 13708") shows both laboratories — checked by a tab query on the labcoda.pl production server on 03.10.2026.

WHAT THE LABORATORIES TEST (PCA items). AB 262: food containing crystalline sugars — detection of irradiation, presence of sugar radicals formed by irradiation, electron paramagnetic resonance spectroscopy (EPR). AB 537: food containing crystalline sugars — detection of irradiation, presence of sugar radicals formed by irradiation, electron paramagnetic resonance spectrometry EPR (qualitative). Both items are qualitative, without numerical ranges.

WHERE A SEEMINGLY CORRECT RESULT IS EASY TO GET. Negative result: absence of the specific spectrum does not prove that the sample was not irradiated — only a multicomponent spectrum is proof (3). Matrix: without sugar crystals irradiation gives no specific signals, and different sugars give different spectra; only dried figs, mangoes, papayas and raisins have been validated (1, 3). Sample: dried fruits must not be rehydrated before testing, and the sugar must remain crystalline at all stages from irradiation (3). Low doses: all false negatives for raisins and papayas in the BCR test concerned a dose of about 0.5 kGy (Table 1). Doubt: the sample's sensitivity to radiation can be confirmed by irradiating a portion and retesting (3). Edition: the text read is EN 13708:2001; the 2022 edition is in force — clause references should use the current PN text.

WHAT WE DO NOT GIVE. We do not reproduce spectrometer parameters, sample preparation, criteria for evaluating spectra or figures of spectra — they are not in the text read. We do not give regulations on food irradiation or a list of foods authorized for irradiation.

Method principle

Ionizing radiation produces radicals — paramagnetic centres — in the crystalline sugar of food, which are detected by electron spin resonance (ESR, EPR) spectroscopy. A strong magnetic field separates the energy levels of electron spins (ms = +½ and −½), leading to resonance absorption of a microwave beam; the spectrum is recorded as the first derivative of absorption, and its position is described by the g value. A multicomponent spectrum characteristic of irradiated sugar proves irradiation; its absence does not exclude irradiation.

Applications

• Dried figs, mangoes, papayas and raisins — validated in interlaboratory studies (1, 3, 4)
• Food containing sufficient crystalline sugar, not rehydrated before testing (3)
• Food containing crystalline sugars — detection of irradiation (qualitative) — 2 accreditation scope records of 2 laboratories in PCA

Key parameters

Standard

Standard number

PN-EN 13708:2022-08

Title (PL)

Artykuły żywnościowe — Wykrywanie napromienienia żywności zawierającej cukier krystaliczny metodą spektroskopii ESR

Title (EN)

Foodstuffs — Detection of irradiated food containing crystalline sugar by ESR spectroscopy

Step-by-step procedure

1. Suitability of the sample

   Presence of crystalline sugar, no rehydration (3). PN-EN 13708:2022-08 — no withdrawal note (PKN, 03.10.2026).

2. Recording the ESR spectrum

   Spectrum as first derivative of absorption; conditions depending on the arrangement (2).

3. Interpretation

   Multicomponent spectrum — proof of irradiation; absence — inconclusive result (3).

4. Confirming sensitivity (where necessary)

   Irradiating a portion of the sample and retesting (3).

Required equipment and apparatus

Reagents, media and consumables

Health and safety (OHS)

• The EN 13708:2001 text read (clauses 1–4) contains no safety warnings

Frequently asked questions