Abstract
High internal phase emulsion (HIPE) becomes highly viscous due to the extreme high volume fraction of dispersed phase. This form of emulsion is useful for cosmetic and pharmaceutical applications. Especially, W/O type emulsions can be valuable in many cases even though the stability has been a problem. Hydrophobic sucrose ester (SE) and polyglycerol ester (GE) with erucic acid side chain (22 carbons and one double bond) have been used for many food applications, like chocolate and fat spreads. We could make very stable W/O HIPE by using these SE or GE in oil phase together with hydrophilic SE and/or GE in water phase. This combination of two types of emulsifier is especially useful to improve the stability at lower temperature. By adding water soluble substances like polyols, which can enhance the stability at higher temperature also, we can make an emulsion with good stability in wide range of temperature. We assume that the combination of two types of emulsifiers can make interfacial membrane stiffer. When using polyoxyethylene derivatives in place of hydrophilic SE or GE, the emulsion turned to O/W. Strong hydrophilicity or lipophobicity of hydrophilic moiety of SE and GE must be important for this synergistic effect. Various kinds of cosmetic oil can be used for this type emulsion. Also this technique can be applied in multiple emulsions.
