Tracking Gluten throughout Brewing Using N‑Terminal Labeling Mass Spectrometry

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. This research used N-terminal
labeling mass spectrometry to characterize protein hydrolysates 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 by sequence
comparison with peptides known to stimulate celiac immune responses.
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. N-terminal labeling mass spectrometry
served as a novel approach to track the fate of gliadin/gluten throughout
bench-scale brewing. Consistently identified fragments could serve
as improved targets for the detection of hydrolyzed gluten in fermented
products.