Enhancing dispersion stability of alpha-tocopherol in aqueous media using maize starch and ultrasonication

Alpha-tocopherol (30-120 mg) was dispersed in an aqueous maize starch solution (0-240 mg starch solids in 30 mL) at various temperatures (60-80 °C) for 3 h, followed by cooling to 30 °C for different periods (0-12 h). The dispersion prepared under an optimized condition was subjected to ultrasonic treatment (up to 5 min in ice bath) to enhance the dispersion stability. When an aqueous α-tocopherol (60 mg) dispersion in a starch solution (120 mg in 30 mL) was prepared at 70 °C with cooling for 3 h and ultrasonic treatment for 3 min, a homogenous and opaque dispersion was obtained with 74% (w/w) of the α-tocopherol added was stably dispersed. The ultrasonic treatment decreased hydrodynamic diameter (from 1253 to 416 nm) and zeta-potential (from -6.28 to -22.40 mV) of the dispersed α-tocopherol particles, improving the dispersion stability. During a storage for 28 days at room temperature, the dispersion remained stable without producing any precipitates or aggregates. When the α-tocopherol dispersion in starch solution was subjected to autoclave treatment (121 °C for 20 min), 25% of the α-tocopherol in the dispersion was transformed to immiscible phase and phase-separated.