Evaluation of oxidative stability, fatty acid profile, and antioxidant properties of black cumin seed oil and extract

Abstract

Black cumin is a strong aromatic seed which can be used as a nutraceutical or medicinal food. Our aim was to evaluate the fatty acid profile and oxidative stability of black cumin seed (BCS) oil as well as the antioxidant activity of water–methanol extract of BCS compared with BHT. In fact, it was going to understand what kind of fatty acids exist in BCS oil and whether is it possible to apply BCS extract as a natural antioxidant or not. The physicochemical properties of BCS oil included an iodine value of 105.17 g/100 g oil, a PV of 11.88 meq/kg, an oxidative stability index of 16.48 h, viscosity of 21.3 mPas, and a refractive index of 1.45. BCS oil contained more than 79% unsaturated fatty acids. Its saturated fatty acids were composed mainly of palmitic acid (8.38%) and stearic acid (2.26%). The BCS extract contained 955.77 mg/kg total phenolics. In a DPPH assay, the IC50 of the BCS extract was measured as 104.76 mg/mL, while for BHT it was 8.06 mg/mL. In the incubation assay, the BCS extract inhibited the formation of oxidation primary products in raw soybean oil at a concentration of 100 mg/mL. To conclude, BCS oil had a high content of polyunsaturated fatty acids and in spite of its high degree of unsaturation, the presence of phenolic compounds in BCS oil led to an increase in its relative oxidative stability. Also, at higher concentrations, BCS extract can compete with BHT in terms of antioxidant effects, and thus can be added into edible oils.