Improving emulsification efficacy of lecithin by formulation design. I: Effect of adding a secondary surfactant

The objective of this study was to seek improvement in the emulsification efficacy of lecithin by formulation design. A Base Emulsion was developed containing lecithin as the primary emulsifier. The lecithin concentration and method of preparation of the Base Emulsion were optimized to obtain minimum particle size and creaming of the emulsion. Selected hydrophilic and hydrophobic synthetic surfactants were evaluated as secondary emulsifiers for their ability to reduce particle size of the Base Emulsion. The selection of type and concentration of the secondary emulsifier was done by application of the HLB method. The hydrophilic emulsifiers selected were Tween 80, Tween 20, Pluronic F68, and Pluronic F127. The hydrophobic surfactants studied included Span 20, Span 80, Pluronic P103, and Pluronic P123. The median droplet size of the Base Emulsion was 2.7 microns. Addition of the hydrophilic emulsifiers caused an increase in particle size and substantial creaming of the emulsions. Addition of three of four hydrophobic surfactants resulted in particle size reduction, but the emulsions showed substantial creaming. Span 20 was found to be the most effective secondary emulsifier. The median particle size of the emulsion was 1.7 microns. These results suggest that supplementing the hydrophilic attributes of lecithin with an appropriate type and amount of hydrophobic surfactant improves the emulsion properties by applying principles of formulation design.