Study of Physicochemical Properties of Nigella Sativa Oil Extracted by Mechanical Pressing and by n-Hexane Solvent

Abstract

Seeds of Nigella sativa L., commonly known as black seed, have been used in traditional medicine. A proximate analyzes of Nigella seeds were determined. Physical and chemical analyses of the crude oils extracted from the seeds, by two different methods (mechanical pressing and solvent extraction) were performed. The proximate analysis for Nigella sativa seed were found to be protein 21.78%, oil 39.4%, ash 4.75%, moisture 6.52%, fibre 8.56% and total carbohydrate 18.99%. Physicochemical analyses of the crude oils extracted from the seeds by two different methods (mechanical pressing and solvent extraction) were also performed. Physicochemical properties of the oils extracted by mechanical pressing and solvent extraction were respectively found as follow: Color by degree for red (8.5 and 7.3), for yellow (20.3 and 20.2) and for blue (1.3 and 1.2), specific gravity (0.877 and 0.909), density (0.9102 and 0.9158 g/cm3), refractive index (1.484 and 1.476) and viscosity (33.66 and 20.82 Cp), saponification number (183.16 and 120.46 mg KOH/g), peroxide value (6.43 and 14.2 mg O2/g), iodine index (96.24 and 89.25 g of I2/100 g of oil) , and an acid value (14.84 and 23.26 mg KOH/g), unsaponification matter (0.48%) and 0.83%, an antioxidant activity (62 and 90) and ester value (168.5 and 97.2 mg KOH/g). The major unsaturated fatty acids were linoleic acid (39.59% and 35.49%), followed by oleic acid (13.06% and 14.76%) and eicosadienoic acid (9.77% and 9.25%), while the main saturated fatty acid was palmitic acid (15. 35% and 15.35%).