Tracking Gluten throughout Brewing Using N-Terminal Labeling Mass Spectrometry

Scope: Gluten-containing grains cause adverse health effects in individuals with celiac disease. Fermentation of these grains results in gluten-derived polypeptides with largely uncharacterized sizes and sequences, which may still trigger an immune response.

Materials and results: This research used N-terminal labeling mass spectrometry to identify protease cleavage sites during each stage of bench-scale brewing, including malting, mashing, boiling, fermentation, and aging. Gluten hydrolysates from each brewing step were tracked and the immunotoxic potential was evaluated in silico. The results indicate that proteolysis and precipitation of gliadins occurring during brewing differ by protein region and brewing stage. The termini of gliadins were hydrolyzed throughout the entire brewing process, but the central regions remained relatively stable. Most hydrolysis occurred during malting, and most precipitation occurred during boiling. The addition of yeast yielded new cleavage sites but did not result in complete hydrolysis. Consistent detection of peptides within the clinically important regions of gliadin corroborated the hydrolytic resistance of this region.

Conclusions: N-terminal labeling mass spectrometry served as a novel approach to track the fate of gliadin/gluten throughout a bench-scale brewing process. Consistently identified fragments could serve as improved targets for detection of hydrolyzed gluten in fermented products.