Emulsifiers are stabilizers of emulsions and are a type of surfactant. The role of emulsifiers is to form a film or double layer when dispersed on the surface of the dispersed material, which can make the dispersed phase carry a charge. This can prevent small droplets of the dispersed phase from coalescing with each other, making the formed emulsion more stable. For example, by adding a certain amount of emulsifier to the primary pesticide (solid) or crude oil (liquid), dissolving them in an organic solvent, and mixing evenly, a transparent liquid called emulsion oil can be produced.
Commonly used emulsifiers include: non-ionic surfactants, those with high oil and water balance coefficients are suitable for preparing water-in-oil emulsions; those with low oil and water balance coefficients are suitable for preparing oil-in-water emulsions. Natural oil and water emulsifiers are mostly hydrophilic gels, which can increase the viscosity of the continuous phase, increase the stability of the emulsion, and are suitable for preparing water-in-oil emulsions, solid particle emulsifiers, and auxiliary emulsifiers.
The largest demand for food emulsifiers is for fatty acid monoglycerides, followed by sucrose esters, sorbitan esters, soy lecithin, mono- and diglycerides of lauric acid, propylene glycol esters of fatty acids, etc.
Sorbitan esters were developed earlier and are used in the food industry, and their annual consumption accounts for about 10% of the total amount of food emulsifiers.
Mono- and diglycerides of lauric acid are a kind of hydrophobic non-ionic surfactant, which naturally exist in breast milk and play a protective role in infant health before the infant's immune system is fully developed. Studies have found that mono- and diglycerides of lauric acid can not only be used as food emulsifiers and added to baked goods to improve the quality of rice and noodle products, but also are a safe, efficient, and broad-spectrum antimicrobial agent. Its antimicrobial effect is not affected by pH and is superior to sorbic acid, benzoic acid, parahydroxybenzoate, and dehydroacetic acid.
Soy lecithin is a natural product and also a kind of non-ionic surfactant. It not only has a very strong emulsification effect but also has certain nutritional value and medical functions. It is an emulsifier worth attention and development, but research needs to be strengthened in the purification and chemical modification of lecithin.