AN-PEP, Proline-Specific Endopeptidase, Degrades All Known Immunostimulatory Gluten Peptides in Beer Made from Barley Malt

Abstract

The haze-forming peptides and proteins present in beer mainly originate from the grains used. Such grains, typically barley and wheat, also incorporate gluten. Although partially hydrolyzed during brewing, glutencontaining protein material remains present in the final beers. Glutensensitive people might therefore not be able to consume beer without an adverse response. AN-PEP, the proline-specific peptidase in Brewers Clarex, is commercially applied to selectively degrade proline-rich, haze-forming peptides and proteins during beer fermentation. The unusually high percentage of proline in known celiac-related gluten epitopes suggests that they form ideal substrates for AN-PEP as well. We confirmed that in beers prepared with AN-PEP, gluten levels were well below 20 mg/kg based on the established competitive R5 ELISA method. We used a sensitive LC-MS/MS method developed in-house to identify the peptides. Only in beers brewed through a conventional process could we find epitope-containing peptides, even in beers that contained less than 20 mg/kg of gluten based on the ELISA. So even though the MS method is qualitative and not quantitative, it provided a more detailed view of the fate of gluten during brewing. Specifically, these data indicate that AN-PEP is able to degrade all known immunogenic gluten epitopes in beer. We conclude that apart from its current application as a beer stabilizer, AN-PEP has the additional benefit of exhaustive degradation of all potentially problematic gluten epitopes.