GELATION AND GEL PROPERTIES OF SOYBEAN GLYCININ IN A TRANSGLUTAMINASE-CATALYZED SYSTEM

Gelation of glycinins as catalyzed by transglutaminase was investigated. The surface lysine and glutamine residues of glycinin increased with heating. In the gelation of native and heat-treated glycinins catalyzed by transglutaminase, the formation of epsilon-(gamma-glutamyl)lysyl cross-links was proportional to the amount of their surface lysine and glutamine residues. Both the acidic and basic subunits participated in the gelation of heat-treated glycinins, while most of the basic subunits did not in the case of native glycinin. Glycinin heated in the presence and absence of N-ethylmaleimide exhibited linear strands of aggregates and branched strands or small aggregates, respectively, and formed hard and elastic gels having a well cross-linked network or soft and viscous gels having a poor network structure, respectively. Modification of lysine or glutamine residues of glycinin affected viscoelastic properties of the corresponding gels. From these results, it was concluded that gel properties may be controlled not only by the amounts of cross-links formed and lysine and glutamine residues available for transglutaminase reaction but also by the nature of substrate protein.