Role of protein-protein interactions on protein aggregation and emulsion flocculation

 In this thesis, the effect of molecular properties on the aggregation and flocculation behaviour is studied. The aggregation behaviour was thought to be mainly affected by the structural stability of the protein. A decreased structural stability results in unfolded proteins which are more prone to aggregation. The flocculation behaviour was shown to be affected by the adsorbed amount at saturation and the adsorption rate. These parameters have been combined in a surface coverage model, which describes the stabilization of emulsions away from the iso‑electric point (pI) to be affected by excess protein in the continuous phase. In addition, a model was proposed for the prediction of the adsorbed amount at saturation. This is influenced by the protein charge and radius and system conditions (i.e. pH and ionic strength). The adsorption rate, which is a measure for the affinity of the protein towards the adsorption to the interface, was shown to increase with increasing relative exposed hydrophobicity and a decrease of the electrostatic repulsion (i.e. decrease of ionic strength or the protein charge). Close to the pI, the applicability of protein-stabilized emulsions is limited. Hence, a steric interaction was introduced to stabilize the emulsion. It was shown that glycation of the protein with a trisaccharide was sufficient to sterically stabilize the emulsions against pH-induced flocculation.