**1. Introduction**

The colloidal mixture of two immiscible liquids gives rise to an emulsion where one liquid is dispersed in another liquid. The solvent or substance that tends to form droplets in the emulsion is defined as the dispersed, while the liquid that surrounds the droplet is defined as the external or continuous phase. An emulsifying agen<sup>t</sup> is a surface-active molecule with the ability to be adsorbed at the oil–water interface of the newly formed emulsion during the emulsification and protects the droplets from immediate coalescence. A surface-active molecule can be considered as a proper emulsifier if it possesses the ability towards frequent adsorption at the oil–water or air–water interface and causes a decrease in interfacial tension. There are low-molecular weight emulsifiers (e.g., soy lecithin) and highmolecular weight emulsifiers (e.g., soy protein and polysaccharides) in soy components. Low molecular weight emulsifiers decrease the surface or interfacial tension to a greater extent than the proteins or polysaccharides due to the partitioning of the entire molecule between the two phases. However, the proteins and polysaccharides would undergo a conformational change at the interface and there might be no clear definition of hydrophilic or hydrophobic groups, resulting in relatively high surface tension compared to that of the low molecular emulsifiers. Although low molecular weight emulsifiers are more effective in emulsion formation, the high molecular weight emulsifiers are more effective in the formation of the viscoelastic film around the oil droplets, which favors the stabilization of the food emulsions. In 2019, the world soybean production was 336.5 million metric tons, which accounted for approximately 58.9% of the world's oilseed production. Soybeans contain about 40% protein and 20% oil and are considered to be a major source of proteins and oils, accompanied by the production of natural surfactants: soy protein, soy lecithin, and soy polysaccharides. Soy protein is the most popular plant protein source to serve as an ingredient in food formulation. It should be noticed that the functional properties of soy-based emulsifiers might be different among the ingredients from different suppliers.

However, the functional properties (e.g., solubility) of commercial soy-based emulsifiers depend on the extraction and processing method utilized for its preparation.
