Formation Of Complexes Of Soybean Protein And Chitosan And Its Application Mechanism In Food Systems

Proteins and polysaccharides are the mainly components of food,which have a significant impact on food quality,solubility,emulsification and structure properties.Soybean industry in China has developed vigorously in the soybean industry,and its nutritional and economic value has obvious application advantages.Chitosan is the most widely sourced cationic polysaccharide in nature,which is prepared by deacetylation of chitin.It has been widely studied and applied in the fields of natural macromolecule,chemical industry and medicine.By exploring the interaction mechanism of protein and polysaccharide and its influencing factors,the interaction between the two is used to construct complexes with different functional characteristics,and the functional characteristics of various complexes are investigated from the perspective of application basis and their application prospects and significance are discussed.This article selects soy protein and chitosan as the research objects to study the effects of soy protein/chitosan complexes(soluble complexes,coacervate)under different conditions,such as pH,mixing ratio,salt ionic strength,heat treatment,and homogenization treatment.The effects of solubility、phase behavior、rheology、foaming and other functional properties of the complexes provide a theoretical basis for the application of the composite in food system.The main research conclusions are as follows:(1)The thesis studies the formation,particle properties,light transmittance and reconstitution effect of soy protein-chitosan soluble complex in transparent acidic beverages.The phase diagram,particle size,ζ-potential,light transmittance and reconstitution effect of the soluble complex were characterized by adjusting pH,recombination ratio,ionic strength,heat treatment and homogenization treatment.The results show that the addition of chitosan can effectively increase the light transmittance of the solution system.The interaction between cationic chitosan and the protein in the system makes the system ζ-potential form a soluble complex(pH3.0-4.0),indicating that the charge is a decisive factor in the stability of the system.After the soluble composite undergoes heat treatment and homogenization treatment,the light transmittance of the composite system is obviously increased,the particle size is obviously reduced,and the heat treatment effect is significantly higher than the homogenization treatment effect.(2)In the thesis,the effects of the rheological behavior and microstructure of the soybean protein-chitosan complex aggregated under different pH,salt ionic strength,and homogenization treatments(shear homogenization and mediation VFD treatment)are studied.The results of the study showed that the viscosity of the proteoglycan complex is much higher than that of the pure protein at pH 7.0.This was because the strong electrostatic interaction between them formed a complex aggregate with a certain structural strength.Shear homogenization and VFD treatment significantly reduced the storage modulus and loss modulus,and the effect of shear homogenization was higher than that of VFD treatment.It was worth noting that when salt ions are added,the VFD treatment of complex aggregates would make the modulus value Therefore,it is inferred that the VFD process may have two effects on the formation of the aggregate structure: destruction effect and promotion effect.In the presence of salt ions,the promotion effect may be dominant.(3)The thesis the foaming and stability of the complex formed by soy protein and microcrystalline chitosan(CNW)by adjusting pH,heating time,microcrystalline chitosan(CNW)addition and other factors.The research results show that the foaming and stability of soy protein after heating with low pH and low ionic strength are significantly higher than those of unheated protein,and the heated protein will undergo structural changes with heating time,passing through Thioflavin T(ThT)And Congo red(CR)fluorescence experiment and AFM experiment can prove the formation of protein β-sheet secondary structure and its "wriggling" fiber micro-topography structure.The addition of microcrystalline chitosan(CNW)can effectively increase the stability of the foam in the system.This may be because the micro-decreased chitosan(CNW)molecule is attached to the protein molecular chain,which reduces the surface tension of the system and makes it easy to get up.The interface changes the spatial structure of the system.