I have been quite curious to the gluten levels of regular barley beers every since I started cutting back on gluten.
If you weren’t aware, the gluten (hordeins) in traditional barley beers get significantly degraded during the brewing process. This is the result of endogenous barley cysteine protease enzymes. Notably, one of these particular enzymes is being used in a dual enzyme therapy currently in clinical trials for cross contamination prevention in non-responsive celiac disease.
Sometimes, other factors are responsible for the breakdown of gluten peptides. These include yeast metabolism, filtration technologies, protein precipitation, and exogenous enzyme additions like Aspergillus niger prolyl endopeptidase enzyme (AN-PEP) in Gluten Reduced (GR) beers like Omission and Daura Dam or papain theoretically being used in some Mexican beers like Corona Extra.6
Having an estimate of the gluten concentration in a specific beer is an important piece of information for those on low-gluten or gluten-free diets. So, I’ve decided to chip in and have now tested 37+ different beers with EZ gluten test strips and have made estimates of their gluten levels based on the results. I began this testing in January 2021 and plan to continue expanding this project.
Barley Beer Results Table
The factors that influence my gluten estimate are listen below.
- Test strip pattern
- All testing was ran and interpreted by myself. While in person interpretation of the test strip is most accurate, i’ve documented and included the strip image for all tests, see HERE.
- R5 ELISA results (if available)
- I’ve factored in any available R5 competitive ELISA results. 3 of the beers have those available from a 2009 Swedish study4. Those beers were Corona Extra, Sol, and Carlsberg Pilsner.
- The 7 GR beers are also included since brewers making GR beers often test the batches to confirm they are <20ppm gluten, though this is unfortunately not required by law.
- Gluten in Beer Blog’s Result (if available)
- Notably, results from another blogger that also tests beer with EZ Gluten (Gluten in Beer Blog5) have been added to help make a more accurate estimate.
- Any known idiosyncratic brewing techniques and/or enzyme additions.
- For example, Corona Extra adding papain (papaya enzyme) during brewing6.
Does EZ Gluten Work for Testing Beer? Yes!
The test kit I use is EZ Gluten. It is a reliable at home gluten test backed up by several research articles1. They show it can accurately measure gluten down to 10ppm, even in hydrolyzed beverages (beer).
EZ gluten may be more suitable for beer testing than assays that use monoclonal antibodies like R5 and G12 (Gluten Tox / Immutest/Etc.)
This is because the “Skerrit” polycloncal antibody employed in EZ Gluten has greater cross-reactivity for hordein from barley gluten than R5/G12. Polyclonal antibodies bind more epitopes on gluten than monoclonal antibodies.
On top of that there is important research showing that R5/G12 antibodies don’t bind D-hordein. D-hordein may be the most abundant barley gluten protein in beer!
Gluten Reduced Beer
7 of the 37 beers I tested were GR beers. The FDA will not allow these beers to be labelled gluten free. They may have made a correct call, as my results for those beers were all positive!
What may explain these surprising results is that AN-PEP’s ability to breakdown the different subcomponents of gluten varies. It is more efficient in breaking down gliadins than glutenins, especially high molecular weight glutenin (HMW-glutenin). It is known that D-hordein has a similar epitope as HMW-glutenin. so, it would make sense that Skeritt antibody also picks it up.
Considering these points, it seems that D-hordein peptides / gluten may still be present in levels >10ppm in these beers.
It is interesting that some beers have discordant or inconsistent results. The main theory I have for this is that different levels endogenous barley peptidase enzymes may be getting activated during barley germination.9 Or related to that, potential wheat contamination in barley harvests depending on which crops are being rotated and other sources of cross contamination. This is what is seen with oat production and why oats need to be certified gluten free2. These contaminating wheat grains may not germinate as readily as barley and their enzymatic activity may be low during malting3. Second, the EZ Gluten test kit may be more or less sensitive depending on how “fresh” or new it is. When I purchased the 25 pack, while it did not reach the expiration for any test, all were not done at the same time. The reagent buffer and test strip coating / antibody has potential to degrade over time.
Traditional barley beer often has gluten concentration higher than 10ppm. However, there are a small percentage whose gluten levels seem to be below 10ppm. Those beers would be Duvel Golden Ale, Duvel Tripel Citra Hop, and Bud Light NEXT. A larger percentage of barley beers may have gluten levels suitable for those on a low gluten diet, less than 20ppm.
Brewers should really think about testing their barley beers regularly for gluten so that consumers can have an estimate of how much gluten they are ingesting. I believe this could open up whole new market of low gluten non-celiac consumers. For now, I hope this chart and my theories can help those on a low gluten diet enjoy a real beer now and again, gain a better perspective of how gluten gets degraded during brewing, and realize how most beer is actually quite low in gluten.
Cheers and Excelsior!
- Allred LK, Park ES. EZ Gluten for the Qualitative Detection of Gluten in Foods, Beverages, and Environmental Surfaces. Journal of AOAC International. 2012;95:1106-17.
- Koerner TB, Cleroux C, Pourier C, Cantin I, Alimkulov A, Elamparo H. Gluten Contamination in the Canadian Commercial Oat Supply. Food Additives and Contaminants. 2011;28:705-710.
- Pre-Harvest Sprouting in Wheat and Barley. Birchip Cropping Group. 2014
- Swedish Beer Testing Study Ridascreen R5 Competitive Results
- Gluten In Beer Blog.
- Moroni D. It’s All in the Enzymes: Why Corona Extra May Have Low Gluten Levels (Papain). CookingAlDante.com.
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.
By Dante Moroni B.S.