Do Gluten Reduced Beers Have High Levels of HMW-Glutenin? (EZ Gluten)

By Dante Moroni

Note: This article is non-peer reviewed and self published. Any statement within are for entertainment purposes and curiosity sake. In no way should any piece from this article be taken as medical advice. This article is also a work in progress and will be updated as necessary by the author.

Brewers that use Aspergillus niger prolyl endopeptidase enzyme to reduce gluten levels in their beer often send samples to commercial laboratories for gluten testing. The assay used in these tests is the Ridascreen R5-Antibody Competitive ELISA, which is sensitive to the highly immunogenic subcomponent of gluten, gliadin, but not as much for glutenin.1 Considering this, it is possible that the R5 ELISA is not adequately detecting glutenin in these AN-PEP beers. This is important because while in most cases of celiac disease (CD) gliadin peptides are the main offender (particularly α-gliadin), some studies have found evidence of reactions to glutenin (HMW-glutenin).2

On the other hand, the commercially available EZ Gluten assay utilizes the Skerritt antibody for detection of gluten. The Skerritt antibody works differently than R5, it has a higher affinity for glutenin than gliadin.1 Thus, I have decided to test several gluten reduced AN-PEP beers using the EZ Gluten lateral flow device. The results were consistent. All of the AN-PEP beers gave a positive result on the assay, indicating the presence of gluten. I also tested a true gluten free beer, one not made with barley, as a control and the result was clearly negative.

Image: Beers tested with EZ Gluten LFD. All of the gluten reduced AN-PEP beers tested positive: Omission Ultimate Light, Omission Pale Ale, Omission Lager, Omission IPA, Daura Damm, Stone Delicious IPA, and Deschutes Juicy Pale. The gluten free beer tested negative: Burning Brother’s Irish Red Ale.

Considering that AN-PEP has been show to have some difficulty digesting the glutenin fraction of wheat, these results can make sense, even with conflicting negative results coming from the R5 assay.3 AN-PEP beers may have low levels of gliadin but still retain significant levels of glutenin.

Table 3 Source: Aspergillus niger Prolyl Endoprotease (AN-PEP), a Unique Enzyme that Breaks Down Gluten Research Review – Metagenetics Institute

The question of whether or not levels of glutenin above 20ppm would cause intestinal inflammation and damage still needs to be investigated. The studies that established the 20ppm safety limit in CD used whole gluten, not purified glutenin. An In vivo glutenin challenge showed exacerbation of CD markers with a 10,000ppm infusion (500mg/50mL) directly into the duodenum. Apart from the high concentration, the glutenin they infused wasn’t pre-digested with AN-PEP which I think is necessary to mimic the hydrolyzed peptides in these beers.4 This is because AN-PEP could and is likely to be working to pre-digest / partially digest the glutenin fraction, making it more susceptible to gastrointestinal proteases, and thus it may not be immunogenic when consumed by individuals with CD.3 More studies on AN-PEP’s effect on glutenin need to be conducted, especially in vivo studies, in order for a conclusion on safety to be made.

.Gluten Reduced beers have no actual regulation governing their gluten content now that the FDA doesn’t let them be called gluten free and there’s also less incentive to test now.

The evidence for glutenin being a toxic or immunogenic fraction is there but the in vivo data isn’t very robust, especially when compared to gliadin. One last thing to add is that beers that haven’t been treated with AN-PEP likely have a more equal ratio of gliadin to glutenin. Due to this, R5 ELISA results should agree with EZ Gluten results in traditional beers. This may be my next experiment if I can get my hands on a Ridascreen R5 Assay Kit.

Individuals with celiac disease should still consult with their physician before consuming any beers brewed with gluten containing ingredients.


  1. Allred L, Ritter B. Recognition of Gliadin and Glutenin Fractions in Four Commercial Gluten Assays. Food Composition and Additives. 2010;93:190-196.
  2. Donnelly S, Suligoj T, Ellis H, Ciclitira P. Identification of Coeliac Disease Triggering Glutenin Peptides in Adults. Scandinavian Journal of Gastroenterology. 2016;51:819-826.
  3. Stepniak D, Spaenij L, Mitea C, Moester M, Ru A, Baak R, Veelen P, Edens L, Koning F. Highly Efficient Gluten Degradation with a Newly Identified Prolyl Endoprotease: Implications for Celiac Disease. 2006;291:4.
  4. Dewar D, Amato M, Ellis J, Pollock E, Gonzalez N, Wieser H, Ciclitira P. The Toxicity of High Molecular Weight Glutenin Subunits of Wheat to Patients with Coeliac Disease. European Journal of Gastroenterology & Hepatology. 2006;18:483-491.