KINETICS OF ULTRASOUND-ASSISTED OIL EXTRACTION FROM BLACK SEED (NIGELLA SATIVA)

ABSTRACT This study investigates the effects of ultrasonication, temperature and solvent to solid ratio on oil yield using response surface analysis and develops a mathematical model to describe the kinetics of oil extraction from black seed (Nigella sativa). The mass transfer coefficients were calculated by fitting a two‐exponential model to the experimental data. An ultrasonication time of 30 min, solvent to solid ratio of 20:1 and temperature at 32C provided the maximum oil yield. Increasing the solvent to solid ratio and ultrasonication time improved the oil extraction rates during the diffusion stage while increasing temperature without ultrasonication improved the oil extraction rates during the washing stage. The kinetics of oil extraction with different particle sizes indicated that ultrasonication improved the values of mass transfer coefficients of washing and diffusion compared with the oil extraction process without ultrasonication. A two‐exponential equation modeled the kinetics of oil extraction from black seed. PRACTICAL APPLICATIONS Extraction of oil from oil‐bearing seeds and materials is important for both the food and biofuel industry. Solvent extraction is the predominant oil extraction method used by the vegetable oil industry. The vegetable oil companies have been looking for alternative methods to increase the efficiency of the extraction processes to reduce the production costs and minimize the wastes. Technological developments in high‐intensity ultrasound generators and transducers increased their use in several industries. The effects of high‐intensity ultrasound in addition to temperature, particle size and solvent to solid ratio on oil extraction were investigated using response surface methodology, and mathematical models for the oil extraction from black seed were demonstrated. High‐intensity ultrasound, response surface experimental design and kinetic models are useful tools that can be adapted by the food industry to optimize and increase the efficiency of the extraction processes.