It’s All in the Enzymes: Why Corona Extra May Have Low Gluten Levels (Papain)

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. Corona Extra is brewed with barley and should not be consumed by those with celiac disease.

By Dante Moroni B.S.

Corona Extra is a beer that seems to test negative for gluten often. It has come up <10ppm on both an R5 ELISA (Ridascreen)1 and Skerritt LFD (EZ Gluten)6. However, I did have an unexpected positive test result recently so let me preface by saying the ppm could vary, although I still estimate it’s between 0-15ppm

I have found evidence to support this. My previous hypothesis was that Grupo Modelo (Corona, Modelo, Pacifico) could be using the enzyme AN-PEP to stabilize their beer and prevent chill haze but that this information was proprietary information. This is done with other “gluten-reduced beers”

Although after recently testing several AN-PEP beers with Skerritt LFD and getting positive results (likely due to D-hordein and/or HMW-Glutenin)7, I don’t think this is the case since Corona Extra tests negative. It seems there is some aspect of Corona Extra brewing that has even more robust gluten degrading properties than barley beers processed with AN-PEP.

Serendipitously, another blog that used to test beer for gluten, had posted a picture of a European Corona Extra bottle from 2013. The ingredients were barley, hops, rice, papain, and propylene glycol (E 405). I believe the “ingredient” leading to the low gluten concentration is, papain. Papain is also likely the reason Grupo Modelo adds propylene glycol to their beer. Brewing with papain has been shown to effect foam quality, so propylene glycol is added to counteract this.11

Crude papain comes from the skin of papayas and it contains several protease enzymes. It is available as a Dietary Enzyme Supplement. Studies have shown that one of these enzymes, caricain is potentially able to degrade gluten!9 On top of that, an old case study from 1976 showed crude papain preventing intestinal damage in a suspected case of celiac disease.8 They have even tested caricain in celiac disease with promising results.10 Considering the close to zero ppm gluten content of Corona Extra and this supporting literature, the use of papain being the gluten reduction agent seems correct. Papain is one of a few enzymes (bromelain-pineapple, actinidin-kiwi) whose digestive potential has somewhat been forgotten about, especially now that AN-PEP and designer proteases (Latiglutenase) have stolen much of the research spotlight.

Why isn’t papain listed as an ingredient anymore? You won’t see papain listed in Corona Extra ingredients due to the EU 1169/2011 food labeling law and similar FDA regulations which no longer required enzymes to be listed as an ingredient.3,4,5 The European legislation went into effect in 2014. 1 year after this picture was taken. If it weren’t for this picture, I don’t think I would have ever connected the dots.2

To sum things up, I believe Corona Extra is reliably between 0-15ppm due to processing with crude papain enzyme. There are likely several other beers on the market getting processed by this or similar enzymes resulting in a low gluten content, probably Modelo Especial, and I did want to think Pacifico also but my recent testing has proved otherwise. The clear bottles of Corona and Modelo may be an additional hint to their enzyme treatment, allowing them to stay fresh even in direct sunlight. Pacifico has a dark bottle. Hopefully some research could be sparked from my theory that would compare AN-PEP to crude papain in brewing gluten free (reduced) beer.


  1. Swedish Beer Testing Study Ridascreen R5 Competitive Results
  2. Corona Extra Picture from 2013 Showing Papain as an Ingredient
  3. European Union Food Labelling Law 1169/2011 Enzyme Change Effective 2014 Article 20bII
  4. FDA Generally Recognized as Safe Food Processing Enzymes
  5. Food Safety Authority of Ireland Statement on Enzymes 1169/2011
  6. Moroni D. EZ Gluten Skerritt Results for Corona Extra and Other Beers 2022. CookingAlDante.
  7. Moroni D. EZ Gluten Skerritt Results for Several AN-PEP Beers 2022. CookingAlDante.
  8. Messer M, Baume P. Oral Papain in Gluten Intolerance. The Lancet. 1976;308:1022.
  9. Buddrick O, Cornell H, Small D. Reduction of Toxic Gliadin Content of Wholegrain Bread by the Enzyme Caricain. 2015;170:343-347.
  10. Cornell H, Czyzewska A, Macrae F, Rydzewska G, Nasierowska A, Bednarczuk A, Stelmasiak T. The Effect of Enzyme Supplementation on Symptoms and Duodenal Histology in Celiac Patients. International Journal of Celiac Disease. 2016;4:40-47.
  11. Papain in Brewing, Effect on Foam Stability.