In a study published in the journal PLOS One, Australian scientists from the Commonwealth Scientific and Industrial Research Organization reported that the commonly used method of detecting gluten levels in beer is often inaccurate.
The researchers examined 60 mainstream beers to see whether their levels of hordein (a common barley-derived type of gluten protein) were accurately detected by the World Health Organization’s approved testing method called enzyme-linked immunosorbent assay (ELISA). Researchers then compared the ELISA findings with the level of hordein found using a different gluten detection test, called multiple reaction monitoring mass spectrometry (MRM-MS).
The ELISA test uses antibodies to detect the presences of gluten, while mass spectometry detects the gluten content of samples by ionizing then sorting them by the particles mass and charge. The results found that the ELISA test often failed to accurately detect high hordein levels when compared to the more sensitive - but also more complicated to perform - MRM-MS test.
For example, two of the beverages marketed as gluten-free beer and two of the low-gluten beers had ELISA readings of zero, but when tested with MRM-MS were found to have significant levels of hordein. Overall, 10 of the 60 commercial beers that were assessed by ELISA showed hordein levels of less than 1 ppm, whereas the mass spectometry results showed that they actually had a much higher hordein content. Meanwhile only half of the commercial gluten-free beers were free of hordein according to both testing methods, which are not comforting results.
Many gluten-free beers are brewed with malted barley, and then the manufacturer extracts the gluten after brewing (through proprietary processes that often use enzymes to destroy the gluten proteins). Whatever their process is, it is designed to remove enough of the protein to be considered gluten-free according to current international standards, which are less than 20 parts per million (ppm). Most often, gluten-free beers are third party tested using the ELISA test. But based on these recent research results, the researchers concluded that the ELISA test, while convenient, is probably no longer a suitable method of measuring gluten in beverages derived from barley.
As a result, the research team is now working on a simple, rapid, and more accurate method of measuring gluten based on mass spectrometry, which they hope the food industry and regulatory boards can eventually use to protect those with celiac disease by accurately labeling foods and beverages as "gluten-free." Until then, gluten-intolerant beer fans should choose gluten-free beers brewed with alternative free grains like sorghum, rice, buckwheat, or millet.