Emulsifiers work by forming a thin molecular layer on the interface of two immiscible phases, thereby reducing the surface free energy of the entire system and creating a new interface. These emulsifier molecules contain both hydrophilic and hydrophobic groups, which can separately adsorb onto the immiscible phases of oil and water, forming a thin molecular layer and lowering the interfacial tension between the two phases. This means that oil molecules are attracted to the hydrophobic part of the emulsifier, while water molecules are attracted to the hydrophilic part. This interaction between the two sides causes a change in interfacial tension.

On the other hand, by forming a protective adsorption layer on the droplet surface, the droplets are endowed with a strong spatial stability. Generally, the more emulsifier added, the greater the reduction in interfacial tension. This allows previously immiscible substances to be uniformly mixed, forming a homogeneous dispersion system, altering the original physical state and thus improving the internal structure of the food, enhancing its quality.

Strongly hydrophilic emulsifiers typically form oil-in-water emulsions, while strongly lipophilic emulsifiers form water-in-oil emulsions. To indicate the hydrophilic-lipophilic balance of emulsifiers, the HLB value (Hydrophilic-Lipophilic Balance value) is commonly used, which also represents the hydrophilicity of the emulsifier. There are various methods to calculate the HLB value:

Hydrophobicity: HLB = Hydrophilic base's hydrophilicity - Lipophilic base's hydrophobicity.

The HLB value is calculated as the hydrophilicity of the hydrophilic group divided by the hydrophobicity of the hydrophobic group.

Each emulsifier's HLB value can be determined by experimental methods. A hydrophobic emulsifier with 100% oil affinity has an HLB of 0 (represented by paraffin), while a hydrophilic emulsifier with 100% water affinity has an HLB of 20 (represented by potassium oleate). The range is divided into 20 increments to indicate the strength of hydrophilicity and hydrophobicity. The higher the HLB value, the stronger the hydrophilicity; conversely, the lower the HLB value, the stronger the hydrophobicity. Most edible emulsifiers are non-ionic surfactants with an HLB value of 0-20. The different HLB values of non-ionic emulsifiers and their related properties are shown in the table. The HLB value for ionic surfactants ranges from 0-40. Therefore, emulsifiers with HLB values <10 are primarily hydrophobic, while those with HLB values ≥10 exhibit hydrophilic characteristics.

Preparing emulsifiers primarily involves emulsifying two liquids, and the quality of emulsification significantly impacts the emulsion's quality. Factors affecting emulsification include interfacial tension, viscosity and temperature, emulsification time, and the amount of emulsifier used. Generally, emulsifiers that can significantly reduce interfacial tension are chosen; the optimal emulsification temperature is around 70°C. If a non-ionic surfactant is used as the emulsifier, the temperature should not exceed its cloud point. Typically, the more emulsifier used, the more stable the emulsion formed.