MALDI based identification of whey protein derived tryptic marker peptides that resist protein glycation

Cow's milk and dairy products are a common cause of food allergy especially for children. The extensive use of milk proteins, especially whey, in food products poses a serious threat to allergic consumers, therefore reliable detection methods are needed in order to ensure meticulous labeling and to protect allergic consumers. The aim of the study was to do a screening of the tryptic peptides derived from whey proteins which were still identifiable using MALDI-TOF/MS and MS/MS analysis despite severe modification through food processing simulating reactions. A bottom-up approach was therefore used. Whey protein mixtures were subjected to the Maillard reaction with glucose, both in the absence or presence of soluble wheat proteins. Despite severe changes on protein level as evidenced by a time dependent increase of protein bound carbonyls, fluorescent compounds, and aggregation as well as a parallel decrease of available lysine residues, several peptides were proven to remain stable. Using MALDI-TOF/MS and MS/MS analysis of tryptic digests of the glycated proteins, two unmodified peptides derived from β-lactoglobulin were identified (15Val–Arg40 and 41Val–Lys60). These stable peptides could serve as analytical targets for the development of new robust analytical approaches for detection of undeclared whey protein residues in foods.

► Cow’s milk proteins are major food allergens.
► Reliable detection methods are needed to ensure correct labeling of foods.
► MALDI-TOF MS was used to screen stable tryptic peptides from whey proteins.
► Two stable peptides from β-LG were identified (57Val Lys76 and 31Val–Arg56).
► They can serve as targets for the development of more robust analytical methods.