Abstract: A simple and eco-friendly procedure was developed to prepare high-molecular-weight octenyl succinic esters of SSPS ( OSA-SSPS) via the esterification between soybean soluble polysaccharides ( SSPS) and octenyl succinic anhydride ( OSA) and then the ultrafiltration membrance of certain molecular weight cut-off ( MWCO) was selected for separating OSA-SSPS． The infrared spectra，particle size，Zeta potential and viscosity of SSPS and OSA-SSPS were compared． The results show that there is an obvious absorption peak of OSA-SSPS at 1733cm － 1 ， indicating that the esterification reaction between SSPS and OSA generated OSA-SSPS; the particle size and absolute potential of OSA-SSPS are higher than that of SSPS; the viscosity of OSA-SSPS is higher than that of SSPS． The stability and morphology analysis of acid milk beverage shows that OSA-SSPS has better protein dispersion stability and uniform distribution of microdroplets than SSPS． The results show that in the esterification reaction between SSPS and OSA，the side chain of SSPS increased，the potential changed and the steric resistance increased．

Key words: soybean soluble polysaccharide, octenyl succinic anhydride, esterification, ultrafiltration, electrostatic repulsion, stability