Quantification of allergenic plant traces in baked products by targeted proteomics using isotope marked peptides

• Targeted proteomics allows simultaneous identification of different plant allergens.
• The developed method allows quantification of targeted allergens in baked products.
• The method is independent of the epitope binding site of proteins.
• The method could be validated with recovery rates of 70–113%.
• The Level of quantification was in the range of 10–50 ppm allergenic food.

The right choice of analytical methods for plant allergen quantification is a deciding factor for the correct assessment and labeling of allergens in processed food in view of consumer protection. The aim of the present study was to develop a validated target peptide multi-method by LC/MS/MS providing high specificity and sensitivity for plant allergen protein detection, plant identification in vegan or vegetarian products using peptide markers for quantification. The methodical concept considers the selection of target peptides of thermostable allergenic plant proteins (Gly m6 soy, Ses i6 sesame and β-conglutin from white lupine) by data base research, BLAST and in silico digestion using Skyline software. Different allergenic concentration levels of these proteins were integrated into our own reference bakery products and quantified with synthesized isotopically labeled peptides after in-solution digestion using LC/MS/MS. Recovery rates within the range of 70–113% and LOQ of 10 ppm–50 ppm (mg allergenic food/kg) could be determined. The results are independent of thermal processing applied during baking and of epitope binding site for the tested allergens.