Fractionation and characterization of soluble soybean polysaccharide esterified of octenyl succinic anhydride and its effect as a stabilizer in acidified milk drinks

The objective of this research was to study the octenyl succinic anhydride (OSA) modified SSPS (OSA-SSPS) formed via SSPS esterified with OSA. Cross-flow ultrafiltration was used to separate polysaccharides after esterification process and then OSA-SSPS with high molecular weight (HMW) as well as OSA-SSPS with low molecular weight (LMW) were obtained. The formation of OSA-SSPS was confirmed by fourier transform infrared spectroscopy which showed a new characteristic peak at around 1730.05cm(-1) (C = O). The viscosity of OSA-SSPS (HMW) was up to 80 mPa s while the value of SSPS was close to 30 mPa s in the 10 wt% concentration. The size distribution of OSA-SSPS indicated that OSA-SSPS (HMW) had a concentrated size in 1 mu m while SSPS expressed three characteristic peaks. Particle size distribution showed that SSPS cross-linked successfully with OSA via the esterification, meanwhile, the side reactions were produced small molecules. The zeta potential of OSA-SSPS (-38.23 +/- 0.24 mV) were 1.5 times as much as SSPS (- 26.67 +/- 0.31 mV). Compared the stability of SSPS with OSA-SSPS (HMW) in the acidic milk drink (AMD), the measurement of dispersion state (e.g. precipitation percent and turbidity) after centrifugation confirmed that OSA-SSPS (HMW) stabilized protein better than SSPS (p < 0.05). Average particle size of protein coated by OSA-SSPS (HMW) kept at 219.1 +/- 3.4 nm at the concentration up to 0.35 wt% and the zeta potential also showed excellent quality of - 4.67 +/- 0.26 mV. Both the stability analysis and microscope image indicated that OSA-SSPS (HMW) had a great stabilizing behavior near the isoelectric point of milk protein because of the larger electrostatic repulsive force and steric repulsive force.