Enhancing Amphiphilic Properties of Glucomannan via Ultrasound-assisted Esterification using Octenyl Succinic Anhydride (OSA)

Modified glucomannan (GM) demonstrates significant potential as a natural, bio-based surfactant, particularly for use as a foaming agent. Although GM is naturally viscous and gel-forming, its amphiphilic character can be enhanced through the introduction of hydrophobic groups via esterification with octenyl succinic anhydride (OSA). This study investigated the effects of varying the GM-to-OSA ratios (1:1, 2:1, 3:1, and 1:2, w/w), pH levels (3, 5, 7, and 9), and ultrasound-assisted esterification durations (30, 60, and 120 minutes) on the degree of substitution (DS), surface tension, and viscosity. The results indicated that these parameters significantly influenced the DS, interfacial tension, and viscosity of the amphiphilic GM. The optimal DS (0.041) occurred at a 1:2 GM:OSA ratio, pH 5, and 60 minutes of sonication. Surface tension dropped from 38 mN/m to 22.82 mN/m with longer sonication, and viscosity increased slightly at pH 7. Given that effective surfactants typically lowered the surface tension of water from 75 mN/m to 25–30 mN/m, the modified GM meets essential criteria for surfactant performance by significantly reducing surface tension, forming emulsions, and adsorbing at liquid, solid, or gas interfaces. These results highlight OSA-modified GM has promise for various industrial applications, particularly in foaming and emulsification systems.