Study On The Mechanism Of Tryptophan And Histidine Inhibiting The Formation Of Dietary Ages And Its Effect On Food Flavor

Advanced glycation end products(AGEs)are a series of compounds produced by nonenzymatic browning of free amino groups of amino acids and free carbonyl groups of biological macromolecules(sugars,proteins,nucleic acids,etc.).AGEs are usually produced during food processing and storage.It will not only reduce the quality of food,but also aggravate the formation of AGEs in the body after entering the body,thereby inducing diabetes,kidney disease,Alzheimer’s disease,cardiovascular and cerebrovascular diseases and so on.At present,the research on natural inhibitors of AGEs mostly focuses on the addition of plant polyphenols with antioxidant activity to foods.However,that addition of plant polyphenol to food could inhibit the generation of AGEs at the early stage of storage,but with the prolongation of storage time,the inhibition effect was not only weaken,but also affected the sensory quality of food,such as color deepening and flavor change.Therefore,we need to find a safe and effective AGEs inhibitor without affecting the sensory quality of food.The amino acid has been found to be a natural product that may have the ability to inhibit AGEs.Therefore,in order to reduce the health risks of AGEs to the body and reduce the content of AGEs in food,this study screened out tryptophan(Trp)and histidine(His)with good AGEs inhibitory effects from 13 kinds of amino acids.The inhibition mechanisms of Trp and His were explored using bovine serum albumin(BSA)-fructose,BSA-pyruvicaldehyde(MGO),BSA-glyoxal(GO)and arginine(Arg)-MGO models.The inhibition of AGEs,sensory quality and flavor components of Trp and His in high protein middle moisture food model were also evaluated.Laying a theoretical foundation for amino acids as natural and effective inhibitors of AGEs in food.The main research methods and results are as follows:The BSA-fructose and BSA-MGO models were used to evaluate the ability of 13amino acids to inhibit the formation of fluorescent AGEs.such as cysteine,phenylalanine,methionine,glycine(Gly),glutamic acid,arginine,lysine,proline,Trp,threonine,aspartic acid(Asp),valine and His.The results showed that,Except for Glu and Asp,the other 11amino acids all showed different degrees of inhibitory activity on the early glycosylation of BSA.Among them,His showed the best inhibition effect on fluorescent AGEs,with the inhibition rate of 15.02%(P<0.05),followed by Trp,with the inhibition rate of8.37%(P<0.05).while only 7 of the 13 amino acids glutamic acid,lysine,proline,Trp,threonine,valine and His)had the ability to inhibit the formation of fluorescent AGEs in the intermediate stage of glycosylation.Trp showed the highest inhibitory activity,reaching81.66%,followed by Gly and His,with the inhibition rates of 77.10%and 64.13%,respectively.The abilities of Trp and His to inhibit the aggregation of fluorescent AGEs,N~ε-carboxymethyllysine(CML),N~ε-carboxyethyllysine(CEL)and soluble proteins were studied by fluorescence spectrophotometer,UPLC-MS/MS and SDS-PAGE.The results showed that Trp and His have the ability to inhibit AGEs and the aggregation of proteins.The inhibition of fluorescent AGEs by two amino acids is dose-dependent,while the inhibition of CML and CEL shows a bell-shaped curve trend.At 1000μg/m L,Amino acidshave the best inhibitory effect on CML and CEL.In addition,The inhibition trend of Trp and His is the same,and the addition of 2 mg/m LTrp and 3.5 mg/m L His in terms of protein aggregation can significantly inhibit the soluble protein aggregation of BSA(P<0.05).UPLC-MS/MS was used to analyze the adducts and possible inhibitory pathways produced by the reaction of Trp and His with MGO.Four addition products of Trp-MGO were obtained in the experiment,including tryptophan-mono-MGO derivative([M+Na]~+=299.200)which were generated by the electrophilic aromatic subs-titution reaction directly at C3.And Trp-mono-MGO derivatives([M+K]~+=297.200),Trp-bis-MGO derivatives([M+H]~+=331.200)and Trp-tri-MGO derivatives([M+H]~+=403.200)generated by complex reactions such as dehydration,Pictet-Spengler condensation,and electrophilic aromatic substitution.However,histidine cannot generate His-MGO derivative through simple addition reaction in a short time,and further research is required.The results showed that the addition of amino acids could increase the degree of Maillard reaction and improve food quality,and reduce the contents of fluorescent AGEs,CML and CEL content in the food model.Trp has a stronger inhibitory ability.However,Trp and His both showed significant inhibition on the protein aggregation only on the 7th day(P<0.05).HS-GC-IMS and electronic nose were used to study the effects of Trp and His on volatile components in Maillard reaction model and high protein intermediate moisture food model in vitro.Trp and His had little effect on the volatile compounds in the model system,and the addition of Trp could promote the formation of volatile compounds in the Maillard reaction model.In the storage process of the food model,the volatile compounds increased from 34 to 51 during the storage process.Among them,the ketone aldehydes and esters with good food flavor increased significantly.Beside,the difference in volatile components was small between the experimental group and the blank group before storage,while the difference in volatile components between the experimental group and blank control group after storage was significant.In conclusion,Trp and His can not only inhibit the generation of AGEs,but also improve the food quality and flavor.Trp and His are expected to become a safe and effective food-borne AGEs inhibitor,which will provide new ideas for the development of functional foods and the research of anti-glycosylation inhibitors in drugs.