Compositional and Immunogenic Evaluation of Fractionated Wheat Beers using Mass Spectrometry

The safety and regulatory status of fermented products derived from gluten-containing grains for patients with celiac disease has remained controversial. Bottom-up mass spectrometry (MS) has complemented immunoassays for the compositional and immunogenic analyses of wheat beers. However, uncharacterized proteolysis during brewing followed by the secondary digestion for MS analysis has made the analysis and data interpretation complicated. In this study, the composition and immunogenic potential of seven commercially available wheat beers were evaluated using bottom-up MS with the aid of fractionation and a multi-step peptide search strategy to capture possible cleavage combinations. Gluten-derived peptides accounted for approximately 50% and 20% of the total number of wheat-derived and barley-derived peptides in investigated beers, respectively. Although relatively large polypeptides cannot be thoroughly characterized using traditional bottom-up proteomics, up to 50% of the identified peptides still contained celiac-immunogenic motifs, and consumption of wheat beers would be risky and not recommended for celiac patients.