Properties of OSA-modified starch and emulsion prepared with different materials: Glutinous rice starch, japonica rice starch, and indica rice starch

Octenyl succinic acid (OSA)-modified starch was prepared using three kinds of rice starch with different amylose content: glutinous rice starch (GRS, 3.67 g/100 g), japonica rice starch (JRS, 17.61 g/100 g), and indica rice starch (IRS, 27.94 g/100 g). The degree of polymerization of OSA and the starch types was 0.0093, 0.0143, and 0.0159, respectively. In addition, holes and cracks were observed in the starch particles owing to esterification. The OSA modification introduced OS group and affected hydrogen bond, but exerted no effect on the crystal form (A-type). The contact angle and emulsifying index revealed that OSA-JRS exhibited the most promising emulsification effect compared to the other samples. Next, soybean oil was added into the OSA-JRS solution to prepare an oil-water emulsion. The results revealed that compared to natural JRS, OSA-JRS exhibited decreased D4,3 and a more uniform distribution. Additionally, its absolute potential value increased to 21.34 mV. Further, the dynamic interfacial tension and contact angle of the OSA-modified samples decreased, whereas the storage and loss moduli of the emulsion increased. The shear resistance, centrifugal force resistance, and storage stability of the OSA-modified emulsion significantly improved. The results demonstrated the potential of the OSA-modified JRS for preparing stable emulsions.