Effects of storage and industrial oilseed extraction methods on the quality and stability characteristics of crude sunflower oil (Helianthus annuus L.)

The influence of industrial oilseed extraction methods on the quality and stability of crude sunflower oil (pre-pressed, solvent-extracted, full-pressed and mixed oils) was studied by means of the determination of free fatty acids, peroxide value, color value, iron, phosphorus, total and individual tocopherol contents, their stability against oxidation (Rancimat induction time) and the fatty acid composition with special emphasis on trans fatty acids. In addition, these crude oils were stored for a period of four months at 40 +/- 2 degrees C and analyzed at monthly intervals for free fatty acids, peroxide value, and Rancimat induction time to evaluate their storage stability. The results revealed that the crude sunflower oils obtained by the full-pressed extraction method had worse quality and stability parameters than the crude oils obtained by other extraction methods. Tocopherol content showed a drastic decrease with full-pressed extraction. Also, the crude sunflower oils obtained by the full-pressed extraction presented a higher total trans fatty acid content than the others. On the contrary, the solvent extraction method influenced the phosphorus and iron contents more than the others. The results indicated, however, that pre-pressing the oil appeared to be better than other methods. This study suggests that it is absolutely necessary for the vegetable oil industry to reevaluate the full pressing method as well as the solvent extraction conditions used for sunflowerseeds in order to retain both nutritive value and oxidative stability.