Preliminary Study On The Formation Mechanism Of AGEs In Maillard Reaction Involved With Ascorbic Acid

The harmfulness of dietary AGEs cannot be ignored.However,there are few researches on the formation mechanism of AGEs in the Maillard reaction involved with Vc.In this study,three model systemswere established based on Vc,glucose（Glu）and lysine（Lys）to study the factors influencing the levels of AGEs under heat processing conditions.In addition,this paper study the dynamics parameters of each model system and the mechanistic pathways of AGEs,which reveal the formation mechanism of AGEs in Maillard reaction involved with Vc.This paper has the vital research significance.The main contents of this paper are as follows:This study selected three models including Glu+Lys,Vc+Lys and Glu+Vc+Lys as the research objects.The effects of temperature and p H on AGEs in each model system were studied.In addition,the change of p H and oxidation-reduction potential（ORP）were monitored.The study reveal the formation of AGEs under different reaction conditions.The results show that the p H has different effects on differert AGEs.Alkaline environment can promote the level of CML and CEL but inhibit the level of PYR.In addition,with the increase of p H,the content and variation trend of the same hazard in different models also have obvious differences.The higher the temperature,the higher the level of AGEs.In the reaction process,small acidic molecules were generated in all three models,which reduced the p H value of the solution system.Meanwhile,oxidation reaction occurred in all three models,and the solution system changed from high reducibility to low reduction.Different heating temperatures were used to investigate the changes of the level of precursor,intermediates and AGEs in the system with time.The main ways of the formation of hazards in the multiresponse kinetic network were studied.A suitable simple series reaction model or（semi-）empirical model was selected to fit the kinetic data in the process of the formation of hazards.The apparent activation energy and apparent rate constant of each step were calculated by combining with the Arrhenius equation.And the results show that the kinetic curves of precursors（Glu,Lys and Vc）were observed to follow first-order kinetic model.Intermediates（FL,GO,MGO and 3-DG）were best described by polynomial.The fitted kinetic curves can be used to predict the content of the intermediates within 90 min.The kinetic curves of the end products（CML,CEL and PYR）were followed zero-order kinetics.And the reaction rate constant（K）and activation energy（Ea）in the three models were calculated.The results show that the reaction rate constant（k）increases with the increase of temperature.The order of activation energy（Ea）of the final product is:CML<CEL<Pyr,which indicating that CML was the most easily formed in the food system,followed by CEL.Finally,in the Glu+Lys and Glu+Lys+Vc models,FL was the main precursor of CML compared with GO.The addition of Vc to Glu+Lys model can promote the generation of 3-DG,which can also promote the generation of PYR.Under the condition of high temperature and long time reaction,Vc can also promote the generation of MGO,but inhibit the generation of CEL from MGO.On the basis of studying the formation of hazards,the Vc or Glu in the model systems were labeled with isotopes,and then reacted in a specific environment.The structure of the intermediate and end products with ¹³C was identified and its content were determined.And the main formation pathway of the AGEs was derived.The structure of intermediates and end products with ¹³C in the three models was identified,and it was found that the intermediates in the ternary model were only directly derived from Glu or Vc,and there was no recombination of the two after cracking.It was found that the intermediate products in the ternary model were only directly derived from Glu or Vc,and there was no recombination of the two products after cracking.It was found that the addition of Vc to U-¹³C-Glu+Lys could not only promote the production of 3-DG,but also inhibit the level of intermediate products including FL,GO and MGO,and end products including CML,CEL and PYR by Glu.In addition,the addition of Vc will also lead to the generation of intermediate products（GO and MGO）and end products（CML,CEL and PYR）.Moreover,in the U-¹³C-Glu+Lys+Vc model,the contents of GO（79.4%）and MGO（92.3%）,as well as intermediate products CML（73.2%）and CEL（77.1%）produced by Vc were much higher than that produced by Glu.The presence of VC inhibited the formation of AGEs by Glu and replaced Glu as the main precursor of AGEs.Finally,this study proposed the formation pathway of AGEs in the U-¹³C-Glu+Lys+VC model.