A UHPLC-MS/MS Method for the Quantification of Wheat Gluten in Commercial Food Products Using Summarized Marker Peptide Contents

Gluten proteins may cause adverse reactions when consumed by predisposed individuals. In dietary gluten-free products, its content must not exceed the threshold value of 20 mg/kg. Compliance with labeling is to be controlled via quantification methods. Some methods use flour as a reference material for quantification. The composition and content of gluten proteins in foods may vary depending on the origin of the gluten source. Because of these variations, the use of a limited number of marker peptides found in flour may lead to false results when quantifying gluten. In this study, a UHPLC-MS/MS method was developed that mitigates the influence of variations in gluten protein content and composition on the quantification result. The general limit of quantification of the method was 10 mg gluten proteins/kg food product. Increasing the number of marker peptides taken into account improves the robustness of the method against varying composition of gluten proteins in commercially available food products.