Thermoluminescence-Based Detection of Irradiation in Valerian Root (Valeriana officinalis) Dietary Supplements: A Pilot Study on Undeclared Treatment and Labelling Compliance.

BACKGROUND/OBJECTIVES: Food irradiation is a recognized method for the microbiological decontamination and preservation of plant raw materials; however, in the European Union, its use is subject to strict legal regulation and to a mandatory labelling obligation. For dietary supplements, which are legally classified as foodstuffs, this issue is particularly important for market transparency and the consumer's right to information. The aim of this pilot study was to assess the presence of post-irradiation characteristics in selected dietary supplements available at retail in Poland, with particular attention to products containing valerian root (Valeriana officinalis L.), and to compare the results obtained with the information declared on the product labels. METHODS: The analysis included 15 analytical samples representing 11 commercial formulations. The study was performed using the thermoluminescence method according to standard PN-EN 1788:2002 in an ISO/IEC 17025-accredited laboratory. RESULTS: Thermoluminescence characteristics consistent with prior irradiation were observed in 7 samples, whereas 8 samples did not show such properties. Positive results concerned exclusively products containing valerian root, including replicate batches of two commercial formulations. None of the positive samples carried any label information about irradiation or exposure to ionizing radiation. The results indicate that some dietary supplements on the market may be subjected to irradiation without this being properly reflected in their labelling. CONCLUSIONS: Given the pilot nature of the study and the limited, non-random sample, the results should be treated as a premise for further analysis rather than as a basis for generalizing to the entire market. The results of this study indicate a need for broader analytical monitoring and targeted control of dietary supplements containing plant raw materials.