Preparation Optimization and Structural Characterization of Octenylsuccinated Deacetylated Konjac Glucomannan

In this study, highly oil-absorbing deacetylated konjac glucomannan octenyl succinate gel (DK-OS) was prepared using deacetylated konjac glucomannan gel (DK-G) as the raw material and octenyl succinic anhydride (OSA) as the esterifying agent. The Box-Behnken experimental design was employed to investigate the effects of four factors (reaction temperature, pH, DK-G concentration, and OSA and DK-G mass ratios m_OSA/m_DK-G) on the degree of substitution (DS) and oil absorption capacity (OAC) of DK-OS. To optimize the process conditions, DK-OS with high OAC and DS was prepared under optimal conditions. The DK-OS was further characterized via infrared spectroscopy, crystalline structure analysis, hydrophobicity assessment, and microscopic morphology. The influence of the four factors on the OAC of DK-OS followed the order of m_OSA/m_DK-G>pH>reaction temperature>DK-G concentration, whereas the order of influence on DS was m_OSA/m_DK-G>DK-G concentration>pH>reaction temperature. The optimal conditions for the esterification process were 39 °C, pH8.5, 2% DK-G concentration, m_OSA/m_DK-G=1.9, and 4 h reaction time. Under these conditions, the resulting DK-OS exhibited a DS of 0.0623±0.0002 and an OAC of 53.88±0.02 g/g. Infrared spectroscopy revealed that the peak intensity of DK-OS at 1727 cm⁻¹ (associated with the ester group) was enhanced after esterification. Additionally, methylene stretching vibration peaks and carboxylate asymmetric stretching vibration peaks were observed at 2926, 2857, and 1566 cm⁻¹, respectively. Notably, the pores that developed on the microstructural surface of DK-OS exhibited increased roughness, whereas the crystal form of the esterified product remained unchanged. The hydrophobic angle increased significantly from 61.5° to 105.3°, thereby reflecting a marked enhancement in surface hydrophobicity. This study provides a technical reference for the development of high-oil-absorption dietary fibers.