Enhanced castor seed oil extraction assisted by the synergistic effect of ultrasound and microwave: Impact on extraction effectiveness and oil quality

Abstract

The present study first time utilizes synergistic effect of ultrasound and microwave for oil extraction from castor seeds, with methanol as solvent. Taguchi's orthogonal array is selected as a tool for design of experiment for castor oil extraction through mechanical stirring, ultrasound, and hybrid (ultrasound + microwave) intensification techniques. The maximum extraction yield effectiveness of 98.37% is achieved based on optimized process conditions: 45 s grinding time, 12:1 solvent-to-seed ratio (v/w), 30 min extraction time, and 50 °C temperature. Along with the yield, significant enhancement in extracted oil quality in terms of oxidation stability and chemical composition is observed. The chemical composition of oil extracted through a hybrid technique shows a lower unsaturation level than ultrasonication. Ultrasound and hybrid technique both significantly increased proportion of ω-6 and ω-9 fatty acids, which has industrial as well as medicinal values. The viscosity of the oil extracted through hybrid solvent extraction is 199 ± 6 cp, which is significantly lower than that of a crushing-based technique (279 ± 6 cp). The energy consumption for the hybrid reactor is reduced by up to 40 % and 28 % than conventional mechanical stirring and ultrasound techniques, respectively. The developed process is industrially viable and environmentally sustainable.