Evolution of Tocopherol Content, Polyphenol Profile, Fatty Acid Profile and Antioxidant Capacity of Fixed Oils of Nigella Sativa L. Seeds During Roasting Time

Abstract

Abstract: Nigella sativa L. is a plant widely used in traditional medicine, and according to our knowledge no study was made on the effect of roasting on the chemical composition and the antioxidant activity of the fixed oils of N. sativa L. seeds. Therefore, we found it useful to investigate this parameter. The seeds are roasted for varying durations (0-40 min) at 180°C. The phenolic content, the fatty acid composition, and the tocopherol composition were determined using chromatographic methods (HPLC and GC). For the antioxidant activity, we used two chemical tests: DPPH (2, 2-diphenyl-1-picrylhydrazyl) test and the β-carotene bleaching test. The maximum chemical content of seed oils was recorded after 15 min of roasting. On the other hand, the concentration of tocopherols decreased over time. The antioxidant activity of treated seed oils was also determined in vitro using DPPH free radical scavenging activity and the β-carotene bleaching tests. In both tests, the highest results were obtained for 15 min roasted sample. The roasting process considerably reduces the content of tocopherols in the fixed oils of the seeds of N. sativa, nevertheless the roasting has a beneficial effect on the content of polyphenols and the antioxidant activity