Effects On The Physicochemical Properties And Functional Properties Of Dioscrin By EGCG Non-Covalent Binding And Ultra-High Pressure Treatment

As one of the main producing countries of yams,China produces a large number of yams every year.Yams contain a lot of nutrients,such as carbohydrates,protein,and a small amount of vitamins.Among them,Dioscrin is the main storage protein of yam,accounting for more than 80%of the total yam protein.And Dioscrin is very rich in amino acids.Although China’s food industry has been booming in recent years,it has greatly improved the quality and nutrition of food while taking into account the taste of food.However,many food nutrients and functional characteristics of food are destroyed or inhibited in the process of food processing.Therefore,in order to keep more functional properties of Dioscrin during food processing and reduce the limitation of food processing,we explored the physicochemical properties and functional properties of Dioscrin in different processing environments.The study results are as follows:1:（1）Physical and chemical properties:in a neutral environment containing EGCG（the ratio of the amount of EGCG and Dioscrin is 1:1,1:3,1:5,1:17 respectively）,the addition of Dioscrin will make EGCG and Dioscrin non-covalent binding,and form EGCG-Dioscrin complex.The EGCG-Dioscrin complex has a smaller particle size,higher negative charge,and stronger solution stability compared to controls.With the increasing concentration of EGCG concentration,the number of free sulfhydryl groups（SH）in its Dioscrin decreased first,but it was always significantly lower than that in the control group.Surface hydrophobicity of the Dioscrin（H₀）continually decreases with increasing EGCG concentration.（2）For functional characteristics,the emulsification of EGCG-Diocrin continued to increase with the increase of EGCG concentration,while the emulsification stability tended to increase firstly and then decrease with the increase of EGCG concentration,reaching the maximum at 1:3,and always higher than that of the control group.The gel hardness of the complex continued to increase with the increase of EGCG concentration,while the gel elasticity increases with EGCG concentration,with the ratio of 1:3 and 1:5,respectively.（3）Through the prediction of molecular dynamics simulation,theα-helix content in the secondary structure of the complex increases,which is similar to the results measured by our CD spectroscopy.And the molecular dynamics simulations show that after the formation of non-covalent complex,the system has a lower energy than the control group.2:When treating Dioscrin protein under certain pressure（100 MPa-10 min,300MPa-10 min,500 MPa-10 min）,we found that the Dioscrin particle size increased under 100MPa,but the particle size decreased when the pressure reached 300 MPa to 500 MPa.Moreover,the results of UV and fluorescence showed that both UV absorption intensity and fluorescence intensity reached the maximum at another 100MPa then decreased.The Zeta-potential continues to increase with the increasing pressure.While the surface hydrophobicity（H₀）increase firstly and then decrease,With the continuous increase of the pressure.The reason is that under the condition of suitable pressure so the protein structure is unfolded.The hydrophobic group is exposed,and the surface hydrophobicity is enhanced.When the pressure is too large,the polymerization of the protein is caused.The above results were verified by molecular mechanical simulation,showing the results of RMSD,RMSF,RG and SASA.3:According to the results of the first two chapters,select Control,EGCG,HP（100 MPa）,HP-EGCG as four treatment of protein,through the study of four different treatment of physical and chemical properties.For the result of UV,high pressure treatment and EGCG non-covalent treatment will make the UV absorption increase,and has a certain superposition between two processing effect.As for the fluorescence intensity,the two treatments will have some antagonistic effect,and the solution formed by Dioscrin after HP-EGCG treatment is more stable.In addition,the experimental results were verified by RMSD and RMSF in the kinetic simulation,and the protein surface area was reasonably predicted by the molecular dynamics simulation.