Differential contribution of Cu2+ and OH- to the formation of Nε-carboxymethyllysine and Nε-carboxyethyllysine in preserved egg white during pickling.

In this study, the relationship between advanced glycosylation end products (AGEs) in preserved egg white (PEW) with protein oxidation and precursors induced by OH- and Cu2+ were performed to clarify the differential contribution of OH- and Cu2+ on the formation of AGEs during pickling. It was found that AGEs were more easily formed in PEW rather than yolk, and the accumulation of Nε-carboxymethyllysine (CML) could be promoted through protein oxidation related to carbonyl compounds, tryptophan induced by Cu2+ at early stage, while carbonyl compounds were more conducive to form Nε-carboxyethyllysine (CEL) under synergistic action of Cu2+ and OH-. At later period, Schiff base promoted the formation of CEL and CML in the presence of Cu2+. Meanwhile, the enrichment of CEL and CML could both be promoted by α-dicarbonyl compounds in presence of Cu2+ and/or OH-. This manuscript will provide theoretical guidance for reducing and limiting hazardous compounds in preserved eggs.