Formation Mechanism Of 3-Monochloro-1,2-Propanediol (3-MCPD) Fatty Acid Ester From Monoglyceride And Its Degredation Rule

3-Monochloropropanediol?3-MCPD?esters is one kind of food contaminants,which may exist in refined oil,bread,infant formula and other food.The formation mechanism of 3-MCPD esters in food processing was not clear.Some studies have reported a free radical mechanism of 3-MCPD esters from diacylglycerol?DAG?and triacylglycerol?TAG?.However,whether the free radical mechanism could be applied in monoacylglycerol?MAG?is still a topic for further researches.MAG is an important food additive widely used in beverage,cake and other food products.Therefore,it's important to clarify the formation mechanism of 3-MCPD esters from MAG to decrease their contents in food.In addition,research on thermal stability of 3-MCPD esters could help to clarify the dynamic process of their formation and degradation,thus to control their contents during food production.The formation mechanism of 3-MCPD esters from MAG was investigated with a series of organic or inorganic chlorides under high temperature.Electron paramagnetic resonance?EPR?,Fourier transform infrared spectroscopy?FT-IR?,quadrupole pole-time of flight mass spectrometry?Q-Tof MS?and its MS/MS,were used to analyze the intermediate of the reaction.The results indicated that the capability of different chlorides to form 3-MCPD esters from MAG varied.The results of EPR showed free radical signals generated from MAG upon heating,indicating free radical formed from MAG upon heating.The FT-IR results of MAG showed MAG could form cyclic acyloxonium structure in high temperature.Based the results,a free radical mediated mechanism involving either five-membered or six-membered cyclic acyloxonium free radicals?CAFR?of 3-MCPD or 2-MCPD monoester formation from MAG was proposed.This CAFR was determined using Q-Tof MS and its MS/MS,which further proved the 3-MCPD ester formation mechanism.A model reaction was built to study the thermal stability of 3-MCPD monoester.3-chloro-1,2-propanediol monostearate was selected as substrate,heated in high temperature.UPLC-Q-Tof MS,GC-MS and ion chromatograph was applied to analyze the degradation products.The results showed 3-MCPD monoester could degrade upon thermal treatment.In addition,different metal ions had different effects on the thermal stability of 3-MCPD monoesters.It is the first time to find metal ions,such as Fe³⁺can promote the thermal degradation of 3-MCPD monoester.This effect of Fe³⁺was verified in different 3-MCPD monoesters.These findings clarify the dynamic process of 3-MCPD monoester formation and degradation,especially the Fe³⁺effect in the process.This study is important for food processing industries to develop mitigation approaches for 3-MCPD esters in the final food products.