Classification and Application of Natural Surfactants

Natural surfactants are widely used in daily life and science. Most of the natural surfactants come from animal and plant organisms, and are relatively complex high molecular organic substances. Because of their high hydrophilicity, they can form emulsions. Most natural surfactants have high viscosity and emulsion stability and are widely used in medicine, food, cosmetics and detergents. Common natural surfactants include lecithin, cholesterol, lanolin, tea saponin, protein, saponins, sugars and alkyl polyglycosides. Most of the natural surfactants are non-irritating, non-toxic and side effects, easy to be biodegraded, and have good compatibility. Therefore, they are the development direction of future surfactants.

Lecithin

Lecithin is present in biological cells such as the eggs, brain and other tissues of animals as well as in plant seeds or germs. Lecithin has an amphiphilic structure. And it has excellent physiological activities such as emulsifying, dispersing and anti-oxidation, and is an excellent natural surfactant and an important emulsifier. When dispersed in water, lecithin can form a phospholipid small cell body (fat body) having a stable bimolecular membrane structure. This fat body can be used as a carrier for medicines, and can also be widely used in skin care, hair care and makeup products. Lecithin can also be involved in the metabolism of cells, with the function of activating cells and anti-aging.

Cholesterol

Cholesterol is a natural emulsifier found in animal brain and nervous tissues as well as lanolin and egg yolk. The molecular structure of cholesterol has a strong hydrophobicity and is therefore suitable for the preparation of oil-soluble emulsifiers. The sebum secretion in the skin is rich in cholesterol and its derivatives, which have the functions of skin care and hair care. Cholesterol is also a co-emulsifier that promotes and enhances the function of other surfactants. It can be applied to cosmetic preparations to help stabilize pigments and lotions.

Lanolin

Lanolin is the secretion of the sebaceous glands of sheep, mostly extracted from wool. The emulsion prepared from lanolin and its derivatives is easy to absorb by the skin, has good stability and good emollient properties, so it is mostly used in creams and oily emulsions. Isopropyl lanolinate has a strong hydrophilic action and can be used in cream preparations. Lanolin alcohol has strong water/oil emulsification properties and also stabilizes oil/water emulsions. Hydrogenated lanolin is a water/oil emulsifier and an oil/water emulsion stabilizer. It has strong water absorption and is easily absorbed by the skin. Lanolin acid soap contains potassium ion, sodium ion, triethanolamine, etc., and has an emulsification effect.

Tea saponin

Tea saponin is an extract of tea, a triterpenoid saponin with strong surface activity and resistance to hard water. Tea saponin has many functions such as emulsification, decontamination, wetting, dispersion, and foaming. Different "oil phase" emulsifiers can be developed using the emulsification properties of tea saponin. Washing the wool fabric with tea saponin maintains the fabric in a vibrant color. Tea saponin has the functions of hair care, anti-dandruff and anti-hair loss, so it is often used in shampoos. Tea saponin is an excellent natural surfactant with an emulsifying ability exceeding that of oleic acid soap, alkyl sulfonate and polyoxyethylene fatty alcohol ether.

Protein

The protein is composed of amino acids, containing both a hydrophilic group and a hydrophobic group, and is a polymeric surfactant. Protein is an essential nutrient for the body and is often used as a food emulsifier. There are many kinds of proteins, such as milk protein, egg protein, casein, soy protein, etc., which have the functions of emulsification, foaming and colloid protection. The functions and applications of different varieties of proteins are also different. Mucin is a glycoprotein that binds water molecules and stabilizes the emulsion. It can be used as a co-emulsifier in skin care products. The yolk high-phosphorus protein is extracted from egg yolk, is easily soluble in water, has remarkable surface ability and stable emulsion performance, and is an excellent nutrient and emulsifier for skin care products.

Phytosterol

The phytosterol can be extracted from soybean oil and composed of sitosterol, stigmasterol, campesterol, VE and the like. It has similar physicochemical properties to cholesterol, has a weak surface activity, and also has antibacterial, anti-inflammatory and hair care effects. It should be particularly noted that phytosterols have a liquid crystal structure and are often used to prepare liposomes.

Alkyl glycoside

Alkyl glycosides are synthesized from sugars. Alkyl glycosides have weak skin irritation, broad-spectrum antibacterial properties, and good compatibility with other types of surfactants. The alkyl glycoside has excellent wetting and foaming properties and has obvious thickening effect, so it has a wide range of applications. Adding alkyl glycosides to the washing powder can improve the detergency of the washing powder. The use of an alkyl glycoside in a meal lotion can improve the solubility and mildness of the preparation and reduce the degreasing power to the skin.

Saponin

The saponin is composed of a sapogenin and a sugar, and the sugar which can constitute the saponin includes glucose, galactose, rhamnose, arabinose, glucuronic acid, galacturonic acid and the like. According to different structures, sapogenin can be divided into triterpenoid saponins and steroidal saponins, wherein the distribution of triterpenoid saponins is more extensive and more diverse than steroidal saponins. There are many plants containing saponins, which are common in Liliaceae, Dioscoreae, Agave, Rosaceae, Dianthus, Polygonaceae, Araliaceae, Cucurbitaceae, etc. Most of these plants have descaling and emulsifying functions and are important natural surfactants.

Carbohydrate

The natural degrading power of carbohydrate natural surfactants is weak, but most of them have thickening, emulsifying and stabilizing effects. Carrageenan is a widely used co-emulsifier. It has a stabilizing effect on colloids (such as toothpaste and shaving cream). It also has a film-forming function and can be applied to hair gel. Alginic acid and its sodium salt are commonly used thickeners and emulsifiers, have a moisturizing effect and can be used in shampoos. Pullulan has an emulsification function and is commonly used in cleansing cosmetics to have a moisturizing function. Cyclodextrins are oligosaccharides composed of glucose units and have a cyclic structure. It has surface activity such as emulsification, solubilization and dispersion, and can be used in essential oils and flavors.

Fatty acid monoglyceride

The chemical formula of fatty acid monoglyceride is C17H33COOCH2CHOHCH2OH, which is a creamy waxy solid with a melting point of 56?. It can be dispersed in hot water and dissolved in ethanol. It is a lipophilic surfactant. Fatty acid monoglycerides are versatile emulsifiers. Because it can be completely biodegraded into glycerin and fatty acids, non-toxic and highly safe, it is recognized as an environmentally friendly "green" product and is widely used as an emulsifier for foods and cosmetics.