Hydrocolloids as emulsifying agents for oil-in-water emulsions

Hydrocolloids are water-soluble biopolymers consisting of high molecular weight polysaccharides. For generations, these biopolymers were also termed gums or stabilizers imparting viscosity, gelification and long-term stability to food systems. Some hydrocolloids were also considered as emulsifying agents, since they help to form and stabilize oil-in-water emulsions. Only in the last two decades questions have been raised as to the mode of their action in low viscosity and low concentrations dispersed systems consisting of oil and water. Gum Arabic is the only gum in use in dilute emulsion systems which was proved to be a good emulsifier - adsorbing onto oil-water interfaces and imparting steric stabilization. However, other gums have been known to reduce surface and interfacial tensions, to adsorb onto solid surfaces and to improve stability of oil-in-water emulsions. Only recently attention has been paid to the structure-surface activity relationship between the gums and their emulsification abilities. Galactomannans, xanthans, pectins, etc, are being considered as emulsifying agents, and correlation between their internal composition and activity are being studied. This review will discuss the drawbacks and prospects of hydrocolloids as food emulsifying agents, as native hydrocolloids and as modified (chemically, enzymatically) macrobiopolymeric amphiphiles.