Judging a beer by its bottle. More accurate gluten testing of fermented products offers new hope for Coeliac disease

Gluten is the general name for the structural proteins naturally found in wheat, barley and rye. These proteins are sometimes difficult to digest and for those with Coeliac disease (CD), incomplete digestion of gluten triggers an immune-based response in the gut where the body begins attacking itself. The resulting inflammation can lead to numerous symptoms affecting sufferers in both the short and long term. It is estimated that one-in-70 Australians are living with CD, however only 20% of people are diagnosed. This under-diagnosis combined with the growing number of people actively selecting to follow a gluten-free diet creates a growing customer base for food and beverage producers.   

Gluten content labels inform food choice and people practicing a gluten-free diet rely upon them to avoid illness. But are labels really accurate in telling us what is in our food? The regulations differ between jurisdictions, especially concerning fermented foodstuffs such as beer. 

Beer production involves multiple steps where gluten proteins that are found in barley malt can be modified, degraded or precipitated. The remaining gluten concentrations are typically above regulatory thresholds for labelling as gluten-free but it has been proposed that they can be further decreased by treatments that aim to precipitate and filter out the gluten. Alternatively, enzymes can be added to digest proline-rich gluten proteins. After testing, beers with 20 – 200 mg/kg gluten can then be labelled ‘low gluten’ and <20 mg/kg gluten as ‘gluten-free’.   

 While it is fun to imagine a laboratory of taste testers sampling beers to establish gluten content, the official method for gluten determination is the enzyme-linked immunosorbent assay (ELISA). However, in foods or beverages containing barley and where a fermentation process is used, the ELISA method can deliver variable results as gluten proteins are broken down into fragments that may be unrecognisable by the ELISA antibodies. This can lead to artificially low readings or false negatives that results in inaccurate labelling of food stuffs which can have severe consequences for those relying on that information to avoid illness.  

 Using a highly sensitive and accurate method for detecting gluten, Chief Investigator Professor Michelle Colgrave, and her CIPPS team members Dr Angela Juhász, Dr Mitchell Nye-Wood, and Dr Utpal Bose investigated gluten content in a range of beers and found that several beers labelled low or reduced gluten contain equivalent or higher amounts of gluten proteins than regular beers.  

 Testing techniques such as liquid chromatography-mass spectrometry (LC-MS) offer an alternative for quality control assessment, but there is an ongoing need for assessing treatment efficiency, batch-to-batch consistency, and the risk of contamination to enable safe and accurate food labelling so individuals can trust their needs are being met.  Indeed, our team have built upon this work to investigate gluten detection in spent grain (https://pubs.acs.org/doi/full/10.1021/jasms.3c00451 LC-MS/MS Reveals Hordeins Are Enriched in Brewers’ Spent Grain) finding that upcycling of spent grain, as a means of waste valorisation, still poses a threat to people with CD. Despite the reduced gluten concentration, there is a risk that it contains gluten protein fragments that can provoke an inflammatory reaction. 

 This research shows that in practice most low-gluten products have detectable gluten and people following a gluten-free diet for medical reasons like CD would benefit from avoiding beer made using cereal grains irrespective of the gluten reduction method. 

Reference: https://www.mdpi.com/2304-8158/12/17/3252  

DOI: 10.3390/foods12173252  

Paper: Low Gluten Beers Contain Variable Gluten and Immunogenic Epitope Content 

Centre members involved: Michelle Colgrave, Angela Juhasz, Mitchell Nye-Wood, Utpal Bose