Some barley beers labeled as “gluten-free” contain small amounts of gluten residues that may trigger celiac disease, which are not detected by the standard antibody-based tests currently in use. This is the conclusion of a study by the Leibniz Institute for Food Systems Biology at the Technical University of Munich. In the study, researchers compared two antibody-based testing methods with a mass spectrometric detection method newly developed at the Institute. The study results show that modern food analytical methods could help further improve the safety of gluten-free products in the future.
Gluten is a collective term for certain proteins found in wheat, rye, and barley. In the EU and according to the international guidelines of the Codex Alimentarius , a food is officially considered “gluten-free” if its gluten concentration is no more than 20 milligrams per kilogram. This limit is set so that most people with celiac disease can tolerate “gluten-free” foods without experiencing symptoms. Celiac disease is a chronic autoimmune disorder of the small intestine in which the body reacts with hypersensitivity to gluten.
Barley beer also naturally contains gluten. To produce gluten-free barley beers, breweries employ various methods. They then use standardized testing procedures to verify whether the beers comply with the legally established gluten limit. These procedures typically involve so-called enzyme-linked immunosorbent assays (ELISA), which detect gluten residues using antibodies. These residues are immunogenic protein fragments (peptides) that are produced, for example, during the enzymatic breakdown of gluten.
New analytical method enables more accurate detection
To verify the accuracy of such standard tests, the research team around principal investigator Katharina Scherf and first author Eleonora Tissen examined four beers containing gluten and 21 gluten-free barley beers. In addition to two established ELISA methods, the researchers used a newly developed method of nano-liquid chromatography-tandem mass spectrometry (nanoLC-MS/MS), which makes it possible to specifically identify celiac disease-active peptides.
The study results show clear differences between the three different detection methods: For example, the G12-ELISA confirmed gluten concentrations below 20 milligrams per kilogram in all beers labeled as “gluten-free.” The R5-ELISA, on the other hand, detected concentrations in four of these beers that slightly exceeded the EU limit. Using the mass spectrometry method, the team also identified a total of 44 peptides that, according to the literature, can trigger celiac disease due to their molecular structure, 29 of which were found in “gluten-free” beers. Seventeen of the 44 celiac-active peptides had a structure that the ELISA antibodies currently in use cannot detect.
Further research needed
“Our results mean that gluten-free barley beers are generally safe. However, they also show that there can be discrepancies between antibody tests and that they do not detect all celiac-active peptides known from the literature,” says Eleonora Tissen, who completed her doctoral studies in Katharina Scherf’s research group. Principal investigator Katharina Scherf adds: “Whether the peptides we additionally identified actually trigger health-relevant reactions cannot yet be conclusively assessed. The good news is that their concentrations were very low and below the EU limit.”
According to the researchers, further investigations are needed. Only then can the potential risk for people with celiac disease be reliably assessed. “In the long term, the combination of established rapid tests and modern mass spectrometry methods could make gluten-free foods even safer. In any case, our study is already providing important impetus for the further development of analytical methods,” says Katharina Scherf, who heads the research group Food Biopolymer Chemistry at the Leibniz Institute.
Publications:
Tissen E., Geisslitz S., Maier B., Scherf K.A. (2026). Identification of celiac disease-active peptides in gluten-free barley beers by nanoLC-MS/MS. Appl Food Res; 6, 101952. 10.1016/j.afres.2026.101952. https://doi.org/10.1016/j.afres.2026.101952
Tissen, E., Geisslitz, S., and Scherf, K.A. (2025). Absolute quantitation of celiac disease-active gluten peptides in gluten-free barley beer by targeted nanoLC-MS/MS. Food Res Int. 222, Part 2, 117703. 10.1016/j.foodres.2025.117703. doi.org/10.1016/j.foodres.2025.117703
Funding:
This project was funded under the European Union’s “Horizon 2020” research and innovation program through the ERA-NET Confund Action No. 696296 via the Joint Programming Initiative “A Healthy Diet for a Healthy Life” (JPI HDHL) as well as by the Federal Ministry of Research, Technology, and Space (BMFTR), Project No. 01EA2205A (ImmunoSafe-CeD). The measurements on the Q Exactive Plus Orbitrap mass spectrometer were funded by the German Research Foundation (DFG) under Project No. 445432254.
More Information:
Why conventional tests can reach their limits
Conventional competitive gluten ELISA tests use monoclonal antibodies that recognize only a few short gluten-specific protein structures or amino acid sequences (so-called ELISA epitopes).
However, they do not detect all celiac disease-active epitopes known from the literature. As a result, a beer may be analytically classified as “gluten-free” even though it still contains small amounts of celiac disease-active peptides. According to the literature, these peptides possess at least one immunogenic epitope that can potentially trigger an immune response. It typically consists of a core sequence of nine amino acids.
What is the Codex Alimentarius ?
The Codex Alimentarius is a global collection of standards and guidelines for food safety and quality. It was established in 1963 by the Food and Agriculture Organization of the United Nations (FAO) and the World Health Organization (WHO).
Contacts:
Expert Contact:
Prof. Dr. Katharina Scherf
Head of the Food Biopolymer Chemistry research group
Leibniz Institute for Food Systems Biology
at the Technical University of Munich (Leibniz-LSB@TUM)
Lise-Meitner-Str. 34
85354 Freising
Tel.: +49 8161 71-2719
Email: k.scherf.leibniz-lsb@tum.de
Press Contact at Leibniz-LSB@TUM:
Dr. Gisela Olias
Knowledge Transfer, Press and Public Relations
Tel.: +49 8161 71-2980
Email: g.olias.leibniz-lsb(at)tum.de
www.leibniz-lsb.de
Information About the Institute:
The Leibniz Institute for Food Systems Biology at the Technical University of Munich (Leibniz-LSB@TUM) comprises a unique research profile at the interface of Food Chemistry & Biology, Chemosensors & Technology, and Bioinformatics & Machine Learning. As this profile has grown far beyond the previous core discipline of classical food chemistry, the Institute spearheads the development of a food systems biology. Its aim is to develop new approaches for the sustainable production of sufficient quantities of food whose biologically active effector molecule profiles are geared to health and nutritional needs, but also to the sensory preferences of consumers. To do so, the Institute explores the complex networks of sensorically relevant effector molecules along the entire food production chain with a focus on making their effects systemically understandable and predictable in the long term.
A Member of the Leibniz Associatation
The Leibniz-LSB@TUM is a member of the Leibniz Association , which connects 96 independent research institutions. Their orientation ranges from the natural sciences, engineering and environmental sciences through economics, spatial and social sciences to the humanities. Leibniz Institutes address issues of social, economic and ecological relevance.They conduct basic and applied research, including in the interdisciplinary Leibniz Research Alliances, maintain scientific infrastructure, and provide research-based services. The Leibniz Association identifies focus areas for knowledge transfer, particularly with the Leibniz research museums. It advises and informs policymakers, science, industry and the general public.
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Note on the use of AI
The press release was first translated from German into American English using DeepL Pro . Prof. Veronika Somoza then reviewed the text for factual and linguistic accuracy, making corrections where necessary.
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Applied Food Research
Experimental study
Not applicable
Identification of celiac disease-active peptides in gluten-free barley beers by nanoLC-MS/MS
1-Apr-2026
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.