Microwave-assisted solvent extraction of castor oil from caastor seeds

Abstract

Castor oil has various uses in the field of cosmetics, plastics, manufacturing of biodiesel, lubricants and medicine. This study investigated the extraction of castor oil using microwave-assisted extraction (MAE). The extraction was performed at 5, 10, 20, 30 min extraction times, 160 W, 230 W and 330 W power intensities and 10, 20 and 40 solvent-to-feed (S/F) ratios (mL of solvent to gram of feed). The oils were characterized for yield, physico-chemical properties, dielectric properties and oxidation stability, and comparison was also made with oil extracted using Soxhlet method. Results show that the mixed solvent (5 % ethanol in hexane) was effective to extract castor oil with 36 % yield by MAE. The maximum oil yield of 37 % was obtained by MAE at 20 minutes with power intensity of 330 W and S/F ratio of 20. The density, refractive index and dielectric properties of oils were not affected by extraction methods and extraction parameters of MAE. However, the viscosity of oil increased, while the pH decreased when the power intensity and extraction time increased due to oil oxidation. The main fatty acid composition of castor oils is ricinoleic acid. The oil extracted by MAE experienced a higher oxidation compared to that by Soxhlet method. With extra caution on oxidation of castor oil, MAE can be an attractive and promising method of 86% less in processing time and higher yield compared to Soxhlet extraction.