The surface activity of soybean saoonin Ab (acetyl-soyasaponin A1:SAb) and the stability of the emulsion Dreoared with SAb were comoared with those of sovasaDonin A1 (SA1). The surface tension of the aqueous SAb solution and interfacial tension of SAb at the water/kerosine interface decreased remarkably with increasing SAb content up to 0.3mM and then decreased slightly up to 0.5mM. The surface and interfacial tensions reached constant values thereafter which were lower than those of the SA1 solution. The amount of adsorbed SAb on the water surface and at the water/kerosine interface were much higher than those of SA1. The foamability and foam stability of SAb were higher than thoseof SA1. The creaming stability of SAb was also higher than that of SA1.The average droplet diameter of the SAb emulsion was smaller than that of the SA1 emulsion. The ratio of oil layer weight separated by centrifugation of the SAb emulsion to total weight of the emulsion was much smaller than that of the SAl emulsion. The ratio of water volume senarated by the standing SAb emulsion to the total volume of emulsion decreased with increasing pH of the droplet surface (pHs) and were constant above pHs4. The zeta potential of the SAb emulsion increased with an increase of PHs.
