Characterization and process optimization of castor oil (Ricinus communis L.) extracted by the soxhlet method using polar and non-polar solvents

Two operating solvent extraction conditions, i.e. average particle size and extraction time, were optimized by a response surface method using Box–Behnken design to obtain high oil yields. The extraction was conducted by the soxhlet method using ethanol, n-hexane and petroleum ether as solvents. Statistical analyses and analysis of variance indicated that the operating conditions are significant factors affecting the yield. For the modeled extraction, yields of 59.8%, 52.3% and 49.9% were determined for optimized average particle sizes and extraction times of 1.30 mm and 2.88 h, 1.26 mm and 2.65 h and 1.25 mm and 2.55 h, respectively. The physicochemical properties of castor bean oils were evaluated. The extracted oils contain refractive indices of 1.4771, 1.4770 and 1.4772, unsaponifiable contents of 0.6, 0.45 and 0.5%, volatile contents of 0.48, 0.55 and 0.28%, free fatty contents of 0.8, 0.3 and 0.27%, phospholipid values of 0.03, 0.05 and 0.03%, peroxide values of 12.4, 3.3 and 3.5 meq O2/kg, iodine values of 85.6, 84.5 and 85.0 g/I2/100 g of oil, saponification values of 174.6, 176.3 and 173.8 mg of KOH/g of oil, acid values of 1.60, 0.60 and 0.53 mg KOH/g, respectively. The analyses indicate that the oil is suitable for use in the oleo-chemicals industry