A new process for concentrating water-soluble materials was developed using osmotic pressure of the water phase in a W/O emulsion, and was applied to the concentration of an amino acid. Two kinds of monodispersed W/O emulsions; a 0.005 molokg-1 monosodium glutaminate aqueous solution, and a 4.50 molokg-1 sodium chloride solution with high osmotic pressure as the dispersed phase, were prepared by the membrane emulsification technique using a hydrophobic porous glass membrane. The two emulsions

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... re mixed and stirred. As a consequence, osmotic pressure as the driving force led to the shrinkage of the monosodium glutaminate-containing water droplets and the swelling of the sodium chloride-containing water droplets. The droplets were then separated by a hydrophobic porous glass membrane with a mean pore size in-between the particle sizes of the shrunken and the swollen droplets. Afterwards, the separated emulsion was permeated through a porous glass membrane with a mean pore size larger than the size of the containing particles. The emulsion was demulsified, after which a 25X concentrated monosodium glutaminate solution was obtained. Calculated value based on the theoretical transport of water through the oil phase with osmotic pressure as the driving force showed good agreement with measured value.