Analysis of Gluten in a Wheat-Gluten-Incurred Sorghum Beer Brewed in the Presence of Proline Endopeptidase by LC/MS/MS

Most gluten-reduced beers are produced using an enzyme called proline endopeptidase (PEP), which proteolyzes the gluten by cleaving at proline residues. However, the gluten content of beers brewed in the presence of PEP cannot be verified since current analytical methods are not able to accurately quantitate gluten in fermented foods. In this work, mass spectrometry was used to qualitatively characterize the gluten in a wheat-gluten-incurred sorghum model beer brewed with and without the addition of PEP. Hydrolyzed gluten peptides and chymotryptic gluten peptides produced from intact gluten proteins were detected in beer brewed in the presence of up to 6 times the manufacturer’s recommended dosage of PEP. The observation of chymotryptic gluten peptides indicates that some gluten proteins remained, at least partially, intact after fermentation and enzymatic treatment. Less intact gluten was observed in beer brewed in the presence of PEP, but more hydrolyzed gluten peptides were consequently observed in PEP-containing beer. Gluten peptides that contained immunogenic sequences known to be associated with celiac disease were detected in PEP-containing beer.