The effect of cold press and solvent extraction methods on some properties of nigella and linseed oils

In this study the effects of cold press, solvent extraction, soxhlet methods and accelerated oxidation conditions on some properties of nigella seed and linseed oils have been investigated. Linoleic (55.85-56.43 %) and linolenic (50.77-52.60 %) were the dominant fatty acids in nigella seed and linseed oils, respectively. The α- ve γ-tocopherol contents of linseed oil were found higher than those of nigella seed and the tocopherol contents of samples signficantly reduced during accelerated oxidation. The total phenolic contents of nigella seed and linseed produced by cold press, solvent extraction and soxhlet methods were 3556.25, 1372.91, 1277.08 and 2004.16, 1079.16, 785.41 mg gallic acid equivalent/g non-oil fraction, respectively. The antioxidant activity and total phenolics of samples were compatible. The tocopherol, total phenolics and antioxidant activity values of cold press samples were found to be higher. Under accelerated oxidation the free acidity and peroxide values of nigella seed oil were higher than those of linseed oil, however, the secondary oxidation products of linseed oil samples were higher. Overall results show that the nigella seed and linseed are valuable sources of essential fatty acids, tocopherols and phenolics. By considering the oxidation parameters, according to its high primary oxidation values and dark brownish colour nigella seed oil should be partially refined. Linseed oil should be consumed fresh before the secondary oxidation products formed. Because of their high total phenolics contents, nigella seed and linseed should be evaluated with their non-oil solid fraction.