Abstract: Stability of an emulsion system composed of undecylenoyl phenylalanine and phenylethyl resorcinol was studied.Main factors that affect stability of the emulsion,such as kinds and dosage of the emulsifying agent,emulsifying agent solubility in oil,selection of the thickening agent system,control of the emulsification homogenizer operating parameters et al.were investigated.Then the formulation and operating conditions for the preparation of the stable emulsion were identified as follows:composition (mass fraction) of emulsifying agant,2.00% of PEG-20 methyl glucose sesquistearate,1.00% of methyl glucose sesquistearate and 0.30% of sodium stearoyl glutamate (1.50% of potassium cetyl alcohol phosphate);composition (mass fraction) of oil phase,3.00% of ethylhexyl methoxycinnamate and 7.00% of octyldodecanol;composition (mass fraction) of thickening agents,2.00% of stearic acid,0.40% of hydroxyethyl acrylate/sodium acryloyldimethyl taurate copolymer and 0.10% of xanthan gum;emulsification temperature,85 ℃;homogenizer speed,9 000 r·min^-1.

Key words: lightening emulsion, emulsifying agent, stability