Hydroxyl radical induced by lipid in Maillard reaction model system promotes diet-derived Nε-carboxymethyllysine formation

• Hydroxyl radical promotes three pathways for carboxymethyllysine formation.
• Lipid induces hydroxyl radical in Maillard reaction model system.
• Lipid promotes carboxymethyllysine formation by inducing hydroxyl radical.

Nε-carboxymethyllysine (CML) is commonly found in food, and is considered as a potential hazard to human health. However, the effect of lipids on CML formation in Maillard reaction is still not clarified. In this study, the content of diet-derived CML and its key intermediates, epsilon-fructoselysine (FL) and glyoxal (GO), is determined with high performance liquid chromatography mass spectrum (HPLC-MS) in model system containing lipid compounds. According to the results, hydroxyl radical (OH) induced by Fenton reagent can promote the three pathways of CML formation. Moreover, in the Maillard reaction system, linoleic acid (Lin), oleic acid (Ole) and glycerol trioleate (Tri) can induce more OH, which promotes CML formation. Their level of promoting CML formation is in the order of Ole > Lin > Tri. On the contrary, glycerol (Gly) can scavenge OH, which inhibit the CML formation. Finally, it is proved that FL content and GO content decreases with heating time in model system, while CML content increases with heating time. Thus, it is concluded that in the Maillard reaction system lipids can induce more OH, which promotes the conversion from FL and GO to CML. Our research may contribute to the development of inhibitory methods for diet-derived CML by scavenging OH.