Cereals & Grains Association
Log In

Effects of a proline endopeptidase on the detection and quantification of gluten during the fermentation of beer.
R. PANDA (1), K. L. Fiedler (1), C. Y. Cho (1), W. L. Stutts (1), R. Cheng (1), E. A. Garber (1). (1) Food and Drug Administration, College Park, MD, U.S.A.

In 2013, the FDA issued a regulation requiring food bearing the claim “gluten-free” must contain less than 20 ppm gluten. It was also recognized that scientifically valid analytical methods did not exist for the quantification of fermented and hydrolyzed gluten. Using the brewing of beer as a model for a fermentation process that involved gluten hydrolysis, the reliability of antibody-based methods and mass spectrometry to detect and quantify gluten were evaluated. Also examined were the effects of a proline endopeptidase (PEP), marketed to hydrolyze immunopathogenic sequences. Sorghum beer containing 0, 20, and 200 µg/mL (ppm) wheat gluten was brewed with and without PEP. Samples collected throughout the brewing process were analyzed by ELISAs and western blot. The final product of the 20 and 200 ppm beer samples, brewed without the addition of PEP, displayed an average reduction in the detectable gluten concentration of 82% and 70%, respectively by ELISA. Addition of PEP at a concentration of 4 mL in 31 gallon of wort increased the loss to 99%. Decreasing the PEP concentration by 8 fold or increasing it by 6 fold also resulted in ≥ 98% reduction in detectable gluten in the final product. Western blot confirmed the results of the ELISA. Hydrolyzed gluten peptides could be observed in the 200 ppm beer samples after a week of fermentation using global mass spectrometry and a subset of these peptides could be observed in the 20 ppm final beer sample using a targeted method. PEP treatment radically altered the hydrolyzed gluten peptide profile to include peptides predominately ending in proline residues. Research is underway to characterize gluten peptides throughout the fermentation process, determine whether immunopathogenic epitopes are present, develop a method to assess the extent of protein hydrolysis, and quantify gluten subjected to fermentation and hydrolysis.

View Presentation