Identification and quantification of aminophospholipid-linked Maillard compounds in model systems and egg yolk products

While the Maillard reaction of free amino acids and proteins is a well-esta blished process, no defined structures from the nonenzymatic browning of am inophospholipids in foodstuffs have been described so far. Phosphatidyletha nolamine (PE)-linked glucosylamines (Schiff-PE), Amadori products (Amadori- PE), 5-hydroxymethylpyrrole-2-carbaldehydes (Pyrrole-PE), and carboxymethyl (CM-PE) as well as carboxyethyl (CE-PE) derivatives were detected and quan tified by liquid chromatography-electrospray mass spectrometry (LC-(ESI)MS) . Model incubations of soy-PE and D-glucose were employed to firmly establi sh the LC-(ESI)MS procedure. Analyses of spray-dried egg yolk powders and l ecithin products derived therefrom show one-fourth of the native D-glucose content of egg yolk to be transformed to Amadori-PE, corresponding to a PE derivatization quota of 11-15.5 mol %; Schiff-PE and Pyrrole-PE were presen t only in low amounts, no CM-PE and CE-PE could be identified in any of the investigated samples. The high glycation rate of egg yolk PE will influenc e the emulsifying properties and perhaps even the oxidation resistance of t he respective products.