Structure of glycinin and ovalbumin gels

Research on the structures of heat-induced gels of glycinin and ovalbumin is reviewed. Both glycinin and ovalbumin gels are thought to have a so-called 'string of beads' structure. In glycinin gels one building unit of the string (a bead) has been thought to be a whole molecule. This means that heat-denatured glycinin molecules do not dissociate into their constituent subunits. An alternative explanation which includes dissociation and reassociation of glycinin has been presented. Heated ovalbumin solutions make transparent gels, turbid gels, clear solutions or turbid suspensions containing aggregates, depending on the pH, ionic strength and protein concentration of the medium. The transparent solutions contain linear polymers of high molecular weight. Ovalbumin gels are thought to be formed by a network of linear polymers. The 'string of beads' model has been accepted as the structure of some globular protein gels including glycinin, ovalbumin, serum albumin, ribonuclease and lysozyme. However, how the heat-denatured asymmetric protein molecules combine to make an ordered string has not been explained.