Determination of tocopherols, fatty acids and oxidative stability of pecan, walnut and sunflower oils

Pecan and walnut oils were extracted by pressing and solvent extraction methods. Fatty acids and tocopherols of oils were determined and oxidation stability of oils was investigated. The results were compared with sunflower oil. Determination of fatty acids was performed by gas chromatography (GG). It was observed that composition of unsaturated fatty acids is high in walnut oil. Tocopherols were determined in oils by high performance liquid chromatography HPLC. Only gamma-tocopherol was found in pecan oil, alpha- gamma- and delta-tocopherols in walnut oil, and alpha- and gamma-tocopherols in sunflower oil. It was observed that more amounts of tocopherols are obtained by pressing. Oxidative stability of oils was followed at 100 degrees C by determining the peroxide value. Walnut oil oxidizes faster than pecan and sunflower oils and the oxidative stability is high in oils obtained by solvent extraction