Preparation of low degree of substitution octenyl succinic starch ester by response surface methodology and its property analysis

Response surface methodology (RSM) was used to explore the best preparation conditions for low degree of substitution octenyl succinic starch ester (OSA ester) by semi‐dry method in this study. The influential factors on product degree of substitution (DS) were sodium carbonate (Na₂CO₃) dosage, reaction time, reaction temperature, dilution ratio. When the optimal preparation conditions were the dosage of Na₂CO₃ at 1.6%, the dilution ratio at 2.65, the reaction temperature at 139°C, the reaction time of 99.5 minutes, the DS was 6.1755 × 10⁻³ ± 2.87 × 10⁻⁵. Compared to the corn starch, Fourier transform infrared spectra (FTIR) showed that absorption peaks of C=O and RCOO⁻ respectively appeared in the octenyl succinic starch ester at 1732 cm⁻¹ and 1558 cm⁻¹. It could be concluded from the deconvoluted FTIR spectra that the esterification reaction destroyed the short‐range order structure of corn starch and the degree of damage was related to the DS of octenyl succinic starch ester. The XRD patterns revealed both the octenyl succinic starch ester and corn starch belonged to A‐type structure, and the degrees of crystallinity decreased with the increased DS. A new peak appeared at 1.06 ppm in the OSA ester, and scanning electron microscopy showed that the OSA ester granules exhibited slightly rough surfaces, with a blurred edges. The Brabender viscosity analysis showed that the gelatinization temperature of the specimens paste was decreased, and the peak viscosity, hot paste viscosity and cold paste viscosity increased, and the contact angle of the OSA ester was larger than corn starch. PRACTICAL APPLICATIONS: Low degree of substitution octenyl succinic starch ester (OSA ester) was a relatively novel amphiphilic surfactant. OSA ester could be prepared by semi‐dry method, which was superior to traditional preparation methods. The structural and physicochemical properties of OSA ester with the different DS were systematically analyzed in this research. This study not only provided a reference for the preparation and application of OSA ester, but also laid a theoretical basis for the development of OSA ester.