An emulsion system is a multiphase system formed by dispersing one or more substances into another dispersed phase. Emulsion systems include oil-in-water (O/W) and water-in-oil (W/O) emulsion systems, with the former being more widely used in food applications. However, emulsification systems are a class of unstable systems, and changes such as delamination and oxidation can occur during long-term storage due to thermodynamic instability and attack by free radicals, so the stability of emulsification systems is the main factor affecting the quality of emulsified foods.

The causes of delamination and flocculation in emulsions using proteins as emulsifiers are related to many factors, such as: the structure of the protein adsorption layer, the viscosity of the continuous phase, the aggregation and rheological properties of the emulsification system, the storage temperature, the protein concentration, the average particle size, the distribution of the particle size, the volume fraction of the oil, the type of oil, and the crystalline form of the fat.

Generally speaking, the particle size of the oil droplet molecules of the emulsification system is the most important factor in determining the stability of the emulsification system, rheological properties, shelf life, color, etc. The smaller the particle size of the oil droplets, the better the stability.

In the homogenization process, protein can be quickly adsorbed to the oil-water interface to reduce the interfacial tension, and form a protective film on the surface of oil droplets to inhibit the aggregation of oil droplets.

On the other hand, at pH values lower or higher than the isoelectric point of proteins, proteins can give the oil droplets an electric charge, and this positive or negative charge will generate repulsive forces to prevent aggregation and flocculation between oil droplets, increasing the stability of the emulsification system.

The stabilizing effect of proteins on the emulsion system may depend on the surface hydrophobicity of proteins, molecular flexibility and the fact that proteins can form interfacial films on the surface of oil droplets.