The Interaction Of Daidzein And Genistein With Soy Protein Isolate And Its Effect On Potein Cold Gel

Protein is an important nutrient in the food system,and its functionality directly affects food quality.Flavonoids interact with protein,they will affect the nutrition and texture of food.Soybeans contain a variety of active isoflavone compounds such as daidzein and genistein,these components will interact with soy protein isolate(SPI),thereby affecting the structure and functional properties of soy protein isolate.Therefore,this article aims to study the interaction mechanism of daidzein(Da)and genistein(Ge)with soy protein isolates and different heat denatured soy protein isolates(HSPI),and the effect of interaction on the properties of protein cold gel.The existing isoflavone-protein interaction theory can be appropriately supplemented to provide a certain theoretical basis and guidance for improving the nutritional value and product quality of soybean protein.The conclusions of this paper are as follows:First,the interaction mechanism between Da and Ge and SPI and its influence on protein structure were studied.The results showed that daidzein and genistein significantly reduced the total sulfhydryl content of SPI(P<0.05),and at the same mass concentration,Ge would cause more sulfhydryl loss in SPI than Da.The quenching method of the interaction between Da and Ge and SPI is static quenching,the acting force is hydrogen bond and van der Waals force,and the binding site is 1.Infrared spectroscopy shows that Da and Ge will change the secondary structure of SPI to varying degrees.Compared with SPI,after adding Da and Ge,the content ofα-helix in SPI was increased,the content of β-pleated sheet was decreased,and the content ofβ-turn was increased,the content of random coil was increased.At this time,the Da/Ge-SPI complex is still dominated by β-conformation structure,but the proportion of random coil content increases.At the same mass concentration,Ge interacts more strongly with SPI than Da,and has a greater impact on the structural changes of the protein.For the aglycons isoflavone,the hydroxylation on the A ring in the benzoyl system can enhance the binding force with SPI,which is also the reason that affects the differentiation of the SPI structure between the two.Secondly,the SPI was heat-treated,and the interaction mechanism between Da and Ge and HSPI under different heat denatured conditions(70℃,85℃,100℃)and its influence on the protein structure were studied.The results showed that both Da and Ge would lead to a significant decrease in the total sulfhydryl content of HSPI under different heat denatured conditions(P<0.05).At the same mass concentration,Ge will cause more sulfhydryl loss in HSPI than Da.The quenching method of the interaction between Da and Ge and HSPI is static quenching.The interaction force between Da and HSPI(70°C,85°C)is hydrogen bond and van der Waals force,and the interaction force between Da and HSPI(100°C)is electrostatic interaction.The interaction force between Ge and HSPI(70℃,85℃,100℃)is hydrogen bond and van der Waals force.According to the comparison of the binding constants between Da and Ge and HSPI,the binding strength of Ge and HSPI(70°C,85°C,100°C)is significantly greater than that of Da and HSPI(70°C,85°C,100°C).At the same time,the increase of temperature promotes the combination of Ge and HSPI,but inhibits the combination of Da and HSPI.However,when the heating temperature reaches 85°C,HSPI has a relatively strong interaction with Da and Ge.Infrared spectroscopy shows that Da and Ge can change the secondary structure of HSPI to varying degrees.After Da and Ge were added,the content of β-pleated sheet in HSPI(70℃)was significantly increased,the content of α-helix,β-turn and random coil were significantly decreased.After Da and Ge were added,the content of β-pleated sheet andβ-turn in HSPI(85℃)were significantly increased,the content of α-helix and random coil were significantly decreased.After adding Da,the content of α-helix and random coil in HSPI(100℃)were significantly decreased,but the content of β-pleated sheet and β-turn were significantly increased.After adding Ge,the content of α-helix,β-pleated sheet,and β-turn in HSPI(100℃)were significantly increased,the content of random coil was significantly decreased.The addition of Da and Ge will increase the proportion of β conformation in HSPI(70°C,85°C,100°C),this indicates that the combination of Da and Ge with HSPI will be more stable.Finally,the effect of the interaction between Da/Ge and HSPI on the properties of protein cold gel was studied.The results show that Da and Ge can form a tight complex with HSPI,thereby significantly reducing the protein particle size.The addition of Ge and Da will significantly affect the zeta potential of HSPI,and Ge has a slightly stronger effect on the zeta potential of HSPI than Da at the same mass concentration.Da and Ge significantly improved the gel strength of the HSPI cold gel,and improved the gel water holding capacity to a certain extent.The addition of Da and Ge makes the microstructure of the HSPI cold gel smoother and more compact.In addition,Ge has a more obvious improvement effect on the gel microstructure than Da at the same mass concentration.