Gel Formation Mechanism Of Soybean Protein Isolate Complexed With Soybean Dietary Fiber

Soybean protein isolate(SPI)and okara were used as raw materials to study the high pressure homogenization(HPH)technology of soybean dietary fiber(SF),factors on gel formation of soybean Protein complex with soybean dietary fiber(SPI-SF),dynamic rheological properties,the intermolecular forces and protein secondary structures and to provide a theoretical basis for study on the gelling mechanism of SF-rich protein gel products.The main research contents are as follows:1.Study on the HPH technique of SF: SF was prepared by okara after being deproteinized and defatted,and 3%(w/v)of SF suspension was treated by a colloid mill twice,and then under HPH.The homogenizing parameters of SF were optimized by the comparison of the particle size distribution of resulting suspension via laser scattering method and micro-morphology observation,the best result was obtained when the SF suspension was homogenized twice at 80 MPa,the average particle diameter of it was25.42 ?m and the micro-morphology of it was thin and dispersed uniformly.2.Study on the influencing factors for forming SPI-SF gels: effects of protein concentration,SF amount,TGase dosage and duration of action on gels were explored according to the texture properties,and the optimum conditions for SPI-SF gel were chosen as followed: 6 %(w/v)of protein,60%(v/v)of ultra-fine SF,20 U/g protein of TGase and 2 h of action duration.3.Analysis of rheological properties of SPI-SF showed: as protein concentrations increased,both G' and G " of SPI-SF system increased with varying degrees as time went on,and all samples except sample with 3% protein formed weak gels and showed no dependence on frequency(f)and angular frequency(?);as SF contents increased,G' and G" of all SPI-SF samples increased greatly,and all gels were good gels with no dependence on frequency(f)and angular frequency(?).4.The results of study on intermolecular forces during SPI-SF gelling showed:electrostatic repulsion between molecules,hydrogen bonding,hydrophobic interactions and mercapto group transformation between disulfide bonds and mercapto group were the main intermolecular forces during SPI-SF gelling,which determined on gel form or not,forming time or gel texture properties.5.Result of protein secondary structure during SPI-SF gelling showed: ultra-fine SF in SPI-SF gel influenced the change and proportion of the secondary structure of protein by affecting the intermolecular forces,that is,the change of protein secondary structure was aresult of the changes in the intermolecular forces.