Studies and Practices of Water-in-Oil Emulsion Stabilized with Amino Acids or Their Salts

Water-in-oil emulsions stabilized by using the gels, which are viscous emulsior of W/O type forned between surfactants (D) and aqueous solution of amino acids (W), were studied. The gels cannot be obtained with any random combination of surfactants and amino acids; their tormation is possible only when the surfactant is a fluid which has lipophilic property and a specific orderly lamellar structure and the amino acids or their salts which are readily soluble in water.By dispersing these gels into the oil phase and then adding the water phase, extremely stable w/o emulsions with wide ranges of water content were obtained. This type of emulsification was termed “gel-emulsification method” by the authors. When this new technology was applied to the preparation of cosmetics, products with outstanding characteristics were obtained.The function of the amino acids in the emulsification was investigated by using physico-chemical methods such as X-ray analysis, NMR, heat of solution, electoron-microscopy and measurement of water content solubilized in the surfactant phase. It may be concluded that the amino acids are effective in forming tight surface atmosphere around water particles and in preventing coalescence of water particles by strong hydration effect of the amino acids, thus stabilizing the w/o emulsion.