Ultrasound-assisted production and characterization of rice bran lecithin-based nanoemulsions

Abstract

Rice bran lecithin (RBL) is a mixture of phospholipids which is obtained as a by-product during the refining of rice bran oil. The emulsifying properties of RBL help in the production of nanoemulsions. Ultrasonication is a high energy approach to produce nanoemulsions with small droplet size and high kinetic stability in comparison to the coarse emulsion. The current study aims to develop stable nanoemulsions using different concentrations of RBL as an emulsifier by ultrasonication (60% amplitude, 40 cycles). Xanthan gum is used as a stabilizing agent for the nanoemulsions. The stability of nanoemulsions under optimum conditions (pH 7, 25 °C) was determined. The nanoemulsions were characterized by determining creaming index, droplet size, polydispersity index (PDI), microstructure analysis, zeta potential, and shear viscosity. The emulsion with the highest concentration of RBL showed maximum kinetic stability against phase separation. The size of nanoemulsions vary in the range of (10–150 nm), the droplet size analysis showed the stability of nanoemulsions on the 14th day of preparation. Microstructure analysis of droplets on different days of storage showed uniform distribution of droplets in the nanoemulsion, thus leading to high kinetic stability. The zeta potential remained negative due to the adsorption of anionic lecithin on the droplet surface. The viscosity of the nanoemulsion formed after ultrasonication exhibited lower viscosity than the preemulsion due to the formation of small droplets.