A new study from the Leibniz Institute for Food Systems Biology at the Technical University of Munich suggests that some barley beers labeled as “gluten-free” may contain low levels of gluten peptides associated with celiac disease that are not detected by commonly used antibody-based testing methods. The findings, published in Applied Food Research and Food Research International, provide impetus to further develop gluten analytical methods.

ELISA vs. Mass Spectrometry

Researchers compared two enzyme-linked immunosorbent assay (ELISA) methods, which are widely used to verify compliance with gluten-free labeling requirements, against a newly developed nano-liquid chromatography-tandem mass spectrometry (nanoLC-MS/MS) method designed to identify specific peptides that are capable of triggering celiac disease.

Gluten Peptides Detected in ‘Gluten-Free’ Beer

Under EU regulations and Codex Alimentarius guidelines, foods may be labeled gluten-free if they contain no more than 20 milligrams (mg) of gluten per kilogram (kg). The threshold is intended to prevent reactions in most people with celiac disease.

For the study, the researchers analyzed four conventional beers and 21 gluten-free barley beers. All gluten-free beers tested below the regulatory limit when analyzed using the G12-ELISA method. However, the R5-ELISA method identified four gluten-free beers with gluten concentrations slightly above the EU threshold.

Using the mass spectrometry method, researchers identified 44 peptides that are potentially capable of triggering celiac disease. Of those peptides, 29 were detected in beers labeled as gluten-free. According to the researchers, 17 of the identified peptides would not be detected by the ELISA antibodies currently used in standard testing methods.

Based on their findings, the researchers suggested that combining established rapid testing methods with advanced mass spectrometry techniques could improve future detection capabilities and support the continued development of gluten analysis methods.

Gluten-Free Beer is Generally Safe, but Risk to People with Celiac is Unknown

Eleonora Tissen, first author of the study, said the findings suggest that gluten-free barley beers are generally safe but highlight differences among available testing methods and their ability to detect all known celiac-active peptides.

Katharina Scherf, Ph.D., the study’s principal investigator and Head of the Food Biopolymer Chemistry research group at the Leibniz Institute, said it remains unclear whether the additional peptides identified by mass spectrometry can trigger clinically relevant reactions in people with celiac disease. She noted that the detected concentrations were very low and remained below the EU regulatory limit.

The researchers said additional studies are needed to determine whether the identified peptides pose a health risk.