Foaming power and emulsifying properties of soyasaponin I.

Abstract

The physical properties and stability of foam and emulsion prepared with soyasaponin I were studied. The surface tension of aqueous soyasaponin I solution showed remarkable decrease when saponin content was below 0.1 mM and reached a constant value at 0.5 mM, which was higher than the value of commercial soyasaponin. The foamability of soyasaponin I in aqueous solution increased with saponin content. The foam stability of soyasaponin I was lower than that of commercial soyasaponin. The change in interfacial tension of the water-kerosine interface against soyasaponin I was similar to that of surface tension. O/W emulsion was obtained with a water-kerosine (1:1) system. The droplet size of the emulsion prepared with soyasaponin I decreased with soyasaponin I content. The static and dynamic stability of the emulsion increased with soyasaponin I content, and both were more stable than commercial soyasaponin emulsion. By centrifuging the emulsion, a gel layer was obtained between the emulsion and water layer. The electric conductivity of the soyasaponin I emulsion, as well as the aqueous solution, increased linearly with an increase in saponin content. The increase in electric conductivity of the emulsion was about one-third of the aqueous solution.