Proteomics Analysis of Celiac Disease-Active Peptides in Food Products with Partially Hydrolyzed Gluten

Foods with partially hydrolyzed gluten may still trigger immune responses in celiac disease (CeD) patients due to residual CeD-active peptides. We applied nanoliquid chromatography-tandem mass spectrometry (nanoLC-MS/MS) to identify 54 CeD-active peptides in 15 barley malt extracts (BME), seven barley malt vinegars (BMV), and 15 soy sauces. Eight common CeD-active peptides were quantitated with targeted nanoLC-MS/MS and stable isotope dilution assay. Total peptide concentrations ranged from 481 mg/kg to 1305 mg/kg in BMEs, whereas three samples showed peptide concentrations near LOQ. Six BMVs had peptide concentrations of up to 0.04 mg/kg, and in soy sauce, they ranged from 0.2 mg/kg to 0.5 mg/kg. Peptide concentrations correlated with gluten content measured by R5c ELISA in BMEs and BMV, while soy sauce showed a gluten content below the LOQ by ELISA. These findings show the presence of CeD-active peptides in foods containing partially hydrolyzed gluten, highlighting the need for comprehensive risk assessment.