Study On The Formation Of 3-chloropropanediol Esters In Oils And Fats

3-chloro-1,2-propanediol fatty acid esters(3-MCPD ester)is a group of process-induced contaminants during the refining and heating of fats and oils,the formation mechanism of 3-MCPD ester has attracted wide attention.The correlation between the content of diglyceride,monoglyceride,free fatty acid and 3-chloropropanol ester in different refined vegetable oils,was researched in this paper.And there was a good correlation between diglyceride and 3-chloropropanol ester with a correlation coefficient of 0.8904.After heating the bleaching soybean oil containing different proportions of diglyceride,it was found that the content of 3-MCPD ester reached to 2.268 mg/Kg when the diglyceride content was 4%and the temperature was 220?.The 3-MCPD ester was generated in large quantities when this critical value was exceeded,and there was a good correlation between the diglyceride and the chloropropanol ester content,so that the diglyceride was determined to be a precursor of the chloropropanol ester.The molecular reaction pathway of formation of 3-MCPD esters was calculated by Gaussian software at B3LYP/6-31+g**level,and there were three pathways.A.Direct nucleophilic substitution reaction;B.Indirect nucleophilic substitution reaction,and C.Mechanism of intermediate(glycidyl ester).The results showed that the ester-based direct nucleophilic substitution reaction was optimal.And the energy barriers for the formation of 3-MCPD esters of dipalmitin,diolein and dilinolein were 74.261,66.017 and 59.856 kJ/mol,respectively.The effects of carbon chain length and unsaturation on the formation of 3-chloropropanol ester were studied.The results showed that the energy barrier gradually decreased with the increase of carbon chain;the increase of unsaturation will reduce the activation energy required for the reaction.But overall it is slightly lower than the saturated fatty acid ester.The results indicating that the 3-MCPD ester formation process is a high-temperature endothermic process.By reducing the temperature,controlling the introduction of precursor diglyceride,the formation of 3-MCPD esters could be prevented.