Abstract: Deestered tea saponin was prepared from tea saponin by aminolysis. The steric hindrance formed by eater groups was eliminated from deestered tea saponin due to removal of two ester groups from tea saponin molecular structure. The product has stronger aggregation ability. The critical micelle concentration(C_cmc) and the surface tension value corresponding to the critical micelle concentration(γ_cmc) of tea saponin were 0.54 g/L and 40.4 mN/m, respectively. Meanwhile, its interactions with water molecules were enhanced by two newly formed hydroxyl groups. The corresponding values of the deestered tea saponin were 0.25 g/L and 47.6 mN/m, respectively. The bubble stability was obviously promoted because of the maintenance of water in the bubble films. The initial bubble height was lower than that of sapoinin, but the time of bubble height which began to decrease was 1 360 min.

Key words: deester tea saponin, surface activity, bubble stability