A comparative study of black cumin seed (Nigella sativa L.) oils extracted with supercritical fluids and conventional extraction methods

Black cumin (Nigella sativa L.) seed oil is of high nutritional and pharmaceutical quality as it is rich in polyunsaturated fatty acids and bioactive components, which are greatly affected by oil extraction methods. To date, comparative studies on the effect of solvent, cold press, and supercritical fluid extraction (SEF) on the quality attributes of black cumin seed oil are scarce. In addition, little information is available in the literature about black cumin seed oils extracted with SFE. Therefore, this study was conducted to compare some physicochemical characteristics, fatty acids composition, triacylglycerol, tocopherol, phytosterol, polyphenols, antioxidant activity, phenolic compounds, volatile compounds, antimicrobial activity, functional groups and melting points of oil extracted from black cumin seed by different methods (SFE, cold press, and solvent extraction). In this study, extracted-black seed oils contain high amounts of C18:2 (60.01-58.75%), OLL (37.45-38.87%), gamma-tocopherol (243.26-276.46 mg/100 g oil), and polyphenols (314.08-400.02 mg GAE/kg oil). Supercritical fluid extraction (SFE) obtained the highest oil yields (37%). In addition, the oil obtained by SFE has relatively higher unsaturated fatty acids, total tocopherols, phytosterols, and polyphenols than that obtained using cold press and solvent extraction methods. Moreover, SFE-oil had stronger DPPH (1.43 mg/mL) and ABTS (2.69 mg/mL) scavenging activity than solvent-extracted oils. The SFE-oil showed high antimicrobial activity against Staphylococcus aureus and Penicillium roqueforti and contained some characteristics of volatile compounds than that extracted with other extraction methods. Overall, the results suggest that SFE-oil from black seeds is an excellent source of bioactive compounds, antioxidants, and antibacterial and has promising applications in the industry.