Some barley beers labeled as “gluten-free” contain small amounts of celiac disease-active gluten residues that are not detected by standard antibody-based tests. This is the result of a study by the Leibniz Institute for Food Systems Biology at the Technical University of Munich.

The researchers compared two established antibody-based test methods (ELISA) with a mass spectrometric method (nanoLC-MS/MS) newly developed at the institute. The results indicate that modern food analytical methods could further improve the safety of gluten-free products in the future.

Gluten is a collective term for proteins in cereals such as wheat, rye and barley. According to EU and Codex Alimentarius guidelines, a food is considered “gluten-free” if it contains no more than 20 milligrams of gluten per kilogram. This limit is intended to ensure that most people with celiac disease tolerate the products. Celiac disease is a chronic autoimmune disease of the small intestine.

Barley beers naturally contain gluten. Breweries use various processes to produce gluten-free variants and then test them for compliance with the limit with ELISA tests.

The team led by study leader Katharina Scherf and first author Eleonora Tissen examined four barley beers containing gluten and 21 beers labeled gluten-free. The G12 ELISA detected values below 20 mg/kg for all “gluten-free” beers. The R5 ELISA, on the other hand, showed a slight exceedance of the limit value for four beers.

Using the mass spectrometry method, the researchers identified a total of 44 peptides that, according to the literature, can trigger celiac disease. Of these, 29 were found in the “gluten-free” beers. 17 of these peptides are not recognized by the ELISA antibodies currently in use.

The scientists emphasized that gluten-free barley beers are usually safe. The concentrations of the additional peptides found were below the EU limit. Nevertheless, the results showed discrepancies between the test methods. Whether the additionally detected peptides actually trigger health-relevant reactions cannot currently be conclusively assessed. Further studies are necessary to reliably assess the potential risk for celiac disease patients.

In the long term, the combination of established rapid tests and mass spectrometry methods could make gluten-free foods even safer, it said.

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. https://doi.org/10.1016/j.foodres.2025.117703

Editor: X-Press Journalistenbüro GbR

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