Emulsifying Potency of New Amino Acid-Type Surfactant (1). O/W Emulsions

Oil-in-water (O/W) emulsions were prepared using a new amino acid-type emulsifier (surfactant), N-[3-lauryloxy-2-hydroxypropyl]-L-arginine L-glutamate (C12HEA-Glu), and the emulsifying potency of C12HEA-Glu was examined in terms of dispersibility, droplet size, interfacial tension, viscosity and hydrophilic microenvironment of droplet surface, whose emulsifying potency was compared with that of general amphoteric and nonionic surfactants. The effects of the constituent oils on the stability of emulsions were also examined. The emulsifying potency of C12HEA-Glu was greater than that of amphoteric N-lauryl-N, N-dimethyl-α-betaine and nonionic polyoxyethylene(10) laurylether, especially, the stability of emulsions containing oleic acid (OA), (C12HEA-Glu/OA/water system), was greatest, while the stability of emulsions containing octane (OC), (C12HEA-Glu/OC/water system), was inferior. OA possesses a hydrophilic carboxyl group and the viscosity of OA is higher than that of OC. The higher visco-elasticity of OA droplet surface and the formation of hydration layer on the droplet contributed to the greater stability of OA emulsions, thereby raising the stability of emulsions for the system C12HEA-Glu/OA/water in spite of the small | zeta-potential | (insufficiently electrostatic repulsion) of droplets.