Research On Maillard Reaction Of Soy Protein Isolate And Properties Of Its Conjugates

During the processing and storage of food containing soybean,the soy protein isolate can react with the coexisting sugar,which will affect the structure and functional properties of SPI.This study investigated the effect of Maillard reaction（MR）on the structure and properties of soybean protein isolate.SPI was subjected to MR with D-galactose/L-arabinose/oatβ-glucan at mass ratios of 1:1,2:1 and 4:1,respectively.The reaction process was monitored,the structure of the conjugate was characterized,and its physicochemical properties（H₀,solubility,emulsifying property,foaming property and rheological property）,physiological properties（SP,FB,BAB,GA andα-GAI）and biological activities（antioxidant activities and antibacterial activities）.The research results will provide some references for the application of SPI in the food industry.The main conclusions were as follows:1.MR of SPI and D-galactose with the mass ratio（1:1,2:1,and 4:1）was conducted.The p H value gradually decreased during the MR process.The UV-Vis absorbance and fluorescence values gradually increased during the MR process.The system with a mass ratio of 1:1 has the fastest MR rate.Structural analysis showed that the conformation of SPI was changed from ordered to disordered after MR,and the structure of SPI molecule was unfolded and stretched,the amino acids covalently bonded to the carbonyl group of saccharides are mainly Lys and Arg in SPI during MR,and SDS-PAGE indicated the formation of high-molecular-weight of constituents during MR.The more the D-galactose content in MR,the higher the degree of glycation and surface hydrophobicity of SPI-D-galactose conjugates.The solubility at different p H,emulsifying and foaming properties of SPI were enhanced after MR,and these properties increased with the increasing of D-galactose content in MR.D-galactose enhanced the viscosity of SPI,and changed its viscoelasticity.Meanwhile,the hydrophilic D-galactose group improved a series of functional properties of amphiphilic SPI,the more D-galactose content in MR,the more significant the enhancement of the functionalities,such as FB and BAB,hypoglycemic effect,antioxidant and antibacterial activity.2.SPI and L-arabinose were prepared by MR at mass ratios of 1:1,2:1 and 4:1 to prepare SPI-L-arabinose conjugates,which were SPI:Ara 1:1,SPI:Ara 2:1 and SPI:Ara4:1.During the MR,the p H value decreased,the UV-Vis absorbance value and fluorescence value increased,and the system of SPI:Ara 1:1 had the fastest MR rate.Structural analysis showed that the conformation of SPI changed from ordered to disordered after MR,and the structure of SPI was unfolded and stretched.The amino acids covalently bonded to the carbonyl of sugars in SPI in the MR process are mainly Lys and Arg.SDS-PAGE indicated the formation of high molecular weight components during MR.The more L-arabinose content added to MR,the higher the DG and H₀ of the SPI-L-arabinose conjugates.The different p H of solubility,emulsifying and foaming properties of SPI were enhanced after MR,and these properties increased with the increasing of L-arabinose content.MR increased the viscosity of SPI,changed its viscoelasticity,and enhanced its FB,BAB,and hypoglycemic effect.The antioxidant and antibacterial activities of SPI were improved after MR,and the more L-arabinose content was added,the stronger antioxidant and antibacterial activities of the conjugates.3.MR of SPI and oatβ-glucan with the mass ratio（1:1,2:1,and 4:1）was conducted.The p H value decreased,and the UV-Vis absorbance and fluorescence values increased during MR.The system with a mass ratio of 1:1 has the fastest MR rate.Structural analysis showed that the conformation of SPI was changed from ordered to disordered after MR,and the structure of SPI molecule was unfolded and stretched,the amino acids covalently bonded to the carbonyl group of saccharides are mainly Lys and Arg in SPI during MR,and SDS-PAGE indicated the formation of high-molecular-weight of constituents during MR.The more the oatβ-glucan content in MR,the higher the DG and H₀ of SPI-oatβ-glucan conjugates.The solubility at different p H,emulsifying and foaming properties of SPI were enhanced after MR,and these properties increased with the increasing of oatβ-glucan content in MR.oatβ-glucan enhanced the viscosity of SPI,and changed its viscoelasticity.Meanwhile,oatβ-glucan improved a series of functional properties of SPI,the more oatβ-glucan content in MR,the more significant the enhancement of the functionalities,such as FB and BAB,hypoglycemic effect,antioxidant and antibacterial activities.D-galactose/L-arabinose/oatβ-glucan has a great influence on the structure of SPI,and further affects the physicochemical properties,physiological properties and biological activities of SPI.