Quantitation of Specific Barley, Rye, and Oat Marker Peptides by Targeted Liquid Chromatography-Mass Spectrometry To Determine Gluten Concentrations

Celiac disease is triggered by the ingestion of gluten from wheat, barley, rye, and possibly oats. Gluten is quantitated by DNA-based methods or enzyme-linked immunosorbent assays (ELISAs). ELISAs mostly detect the prolamin fraction and potentially over- or underestimate gluten contents. Therefore, a new independent method is required to comprehensively detect gluten. A targeted liquid chromatography tandem mass spectrometry method was developed to quantitate seven barley, seven rye, and three oat marker peptides derived from each gluten protein fraction (prolamin and glutelin) and type (barley, B-, C-, D-, and gamma-hordeins; rye, gamma-75k-, gamma-40k-, omega-, and HMW-secalins). The quantitation of each marker peptide in the chymotryptic digest of a defined amount of the respective reference gluten protein type resulted in peptide specific yields, which enabled the conversion of peptide into protein concentrations. This method was applied to quantitate gluten in samples from the brewing process, in raw materials for sourdough fermentation, and in dried sourdoughs.