Strenthening Cold-set Soy Protein-stabilized Emulsion Gels By Modulating Protein Composition

Protein-stabilized emulsion gels can be applied as a kind of delivery carriers for labilelipid-soluble bioactive compounds. In addition, many food products exist as emulsion gels.Many articles have been available indicating that soy protein-stabilized emulsion gels havebroad application prospect. But information about the effects of protein composition on theproperties and mechanism of cold-set soy protein-stabilized emulsion gels is very scarce. Thisthesis was mainly concentrated on the formation, characterization and gelling mechanism ofgel-like emulsions and MTGase-induced emulsion gels stabilized by soy protein withdifferent7S/11S ratio. The main results were as follows:Glycinin preheated and subsequently homogenized by microfluidizer could form gel-likeemulsions, but β-conglycinin and mixture protein could not. The properties andmicrostructures of gel-like emulsions were closely related to preheating temperature. Theoptimal temperature for gel-like emulsions stabilized by glycinin was85℃. Confocal laserscanning microscopy（CLSM）indicated that the emulsions stabilized by β-conglycinin,glycinin and mixture protein exhibited remarkable microstructure differences.The rheological properties and microstructures of gel-like emulsions stabilized by soyprotein with different glycinin content were characterized and compared. The resultssuggested that gel-like emulsions stabilized by preheated soy globulins could be formed onlyat glycinin contents above65%. Gel-like emulsions exhibited microstructure differences withincreasing of glycinin content. Turbidity, optical microscopy, CLSM, emulsifying activityindex(EAI), creaming index(CI) and d4,3were evaluated in order to investigate the mechanismof gel-like emulsions. Increasing glycinin content in the globulin mixtures resulted in aprogressive increase in the extent of bridging flocculation, emulsion instability and creamingindex. Preheated glycinin played an important role in the formation and maintenance ofgel-like network, through inter-droplets hydrophobic interactions.Influence of soy β-conglycinin/glycinin ratio on properties, microstructure and gellingmechanism of Transglutaminase-set soy globulin-stabilized emulsion gels was explored. The enzyme incubation resulted in the gelation of all soy globulin-stabilized emulsions. Basically,increasing the glycinin content progressively increased the gel stiffness, but significantlydecreased the WHC. CLSM observations showed that increasing glycinin content led to theformation of emulsion gel network with a more inhomogenous and porous microstructure.The improvement of the gel stiffness by increasing glycinin content was largely associatedwith the enhanced flocculation of oil droplets, more proteins entrapped within the network, aswell as more importance of covalent cross-links for the gel network at higher glycinincontents.It was confirmed that the formation and properties of soy globulin-stabilized emulsiongels could be controlled by varying protein composition. The results in this thesis provided animportant theoretical basis for the development of new functional foods.