An investigation on the effect of cold press and soxhlet methods of extracting Iranian black seed oil on physicochemical and antioxidant properties

Black cumin which is known as Nigella sativa L. is an oilseed that plays the role of complementary food regime in many countries and it is even favorite in non-productive countries. Black cumin is an annual herbaceous plant, native to south and southwest Asia , is the important sources of nutrients. It is so popular among the newest edible oils as its important role in nutrition and health of human beings and the fatty acid and fat soluble bioactive compounds also black cumin seeds contain 30 to 40 percent oil. There are several reports illustrate that black cumin oil is source of antioxidant and anti-cancer activity. Beta-cytosterol, stigmasterol and compressor are major sterol compounds in black cumin oil. In order to investigate the extract method on physicochemical and antioxidant properties and fatty acid profile of Black cumin oil, two methods of cold press and soxhlet were used and the output were determined. In soxhlet method, the solvents were petroleum ether, Diethyl ether and hexane and after that the oil with the most extract output as the sample for soxhlet method in other experiments were used. Fatty acid compound of extracted black cumin oil was determined after being methylated by

chromatography device. Physicochemical properties of extracted oils like acidity, Peroxide content, iodine index and soap number were calculated. In order to measure the antioxidant properties, total phenol compounds were measured by Folin's phenol reagent method and free radical inhibition were measured by 2 and 2-diphenyl-1-picyril hydrazyl (DPPH) which is a Lipophile radical and has the most absorption at wave length of 517 nm. For measuring the total phenol in Folin's phenol reagent method, standard curve of gallic acid was used and the results are expressed in equivalent grams of gallic acid in grams of dry matter the most absorption was measured at wave length of 760 nm with a UV– vis spectrophotometer. also all the analyses were done in triplicate.

In this study, nigella seeds content of 3.8% moisture, 33.4% ash, 20.4% protein and 38.8% fat. Extracting oil by petroleum ether had the most output in extraction compared to other solvents in soxhlet and cold press methods, but with a decrease in antioxidant properties compared to cold press sample. Total phenol compounds in cold press were 114/50 and in solvent 26/16 mg of gallic acid in kg oil and the amount of free radical inhibition in press oil was 74.40% and in soxhlet oil was 44/42%. Physicochemical and nutritional properties of every oilseed is affected by its fatty acid compound. This oil contains significant amounts of unsaturated fatty acids such as linoleic acid (18: 2n-6) and oleic acid (18: 1n-9) and in both methods, these two fatty acids were dominant. linoleic acid is a favorable nutrient in oil.