Emulsifier
Emulsifiers belong to the surfactants, usually with a grease-loving (lipophilic) and a water-loving (hydrophilic) part, which can nest around boundary layers between aqueous and greasy parts. Grease and water repel each other, making an emulsion without emulsifier easily fall apart. An emulsifier prevents this rejection because it projects the water-loving side towards the water and the fat-loving side towards the fat. The extent to which the hydrophilic or lipophilic character dominates is represented by the HLB value of the surfactant (HLB = Hydrophilic-Lipophilic Balance). A high HLB value (10 to 18) indicates a hydrophilic substance suitable for emulsifying fats or oils in water. Substances with a low HLB (3 to 8) are lipophilic and suitable for water-in-oil emulsions.