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Physicochemical properties and stability of black cumin (Nigella sativa) seed oil as affected by different extraction methods

Mustafa Kiralan, Gülcan Özkan, Ali Bayrak, Mohamed Fawzy Ramadan
Industrial crops and products 2014 v.57 pp. 52-58
Nigella sativa, absorption, benzoic acids, carotenoids, chlorophyll, cold, fatty acid composition, free fatty acids, high performance liquid chromatography, microwave treatment, oxidation, oxidative stability, peroxide value, phenolic compounds, refractive index, seed oils, solvents, sterols, storage time, tocopherols
Black cumin (Nigella sativa) oil (BCO) was recovered using different extraction techniques including solvent free system (cold-pressing) and solvent extracted systems (Soxhlet and microwave assisted). Oils were analyzed for the composition of fatty acids and bioactive compounds (sterols, tocopherols, chlorophyll, carotenoid and phenolics profile) and for some physicochemical properties [free fatty acid, peroxide value (PV), refractive index, and ultraviolet (UV) absorption at K232 and K270]. Antiradical power (AP) of oils was also evaluated, wherein cold-pressed oil had stronger AP than solvent extracted oils. Phenolic profiles analyzed by HPLC revealed that thymoquinone was the main phenolic compound wherein high levels of benzoic and p-hydroxy benzoic acids were found in cold pressed-BCO. Oxidative stability (OS) of oils was evaluated during accelerated oxidation conditions (oven test at 60°C and Rancimat test at 110°C). The greatest induction period was 19.6h for Soxhlet-extracted BCO, and the lowest induction period was 3.48h for cold-pressed BCO. PV of cold-pressed BCO reached 85.3meq O2/kg oil, while PV of the other extracted oils were under 27.0meq O2/kg oil at the end of storage period.