The objective of this paper was to evaluate the oxidative stability of some selected, cold-pressed and fully refined oils. The scope of the paper comprised the evaluation of chemical quality and oxidative stability of oils on the basis of the Rancimat (120°C) and thermostatic (63°C) test results. The material investigated included cold-pressed oils: rapeseed, sunflower, soybean, and extra virgin olive oil, as well as fully refined oils of the same kind. There were determined: colour using a spectro-photometric technique, acid value, peroxide value, anisidine value, Totox indicator, iodine value, and the composition of fatty acids. On the basis of the Rancimat test results, it was evidenced that the extra-virgin olive oil had the longest induction time (6.5 h). With regard to this parameter, the determined sequence of oils investigated was as follows: fully refined rapeseed oil (4,7 h), cold-pressed rapeseed oil (4.5 h), fully refined soybean oil (3.8 h), cold-pressed soybean oil (2.7 h), refined olive oil (2.5 h), fully refined (2.4 h) and cold-pressed sunflower oil (2.2 h). The analysis of the sunflower and rapeseed oils showed that the cold-pressed and fully refined oils of these two kinds did not statistically significantly differ from each other in the induction time determined by the Rancimat test. The extra virgin olive oil was characterized by a definitely longer induction time compared to the refined olive oil. On the basis of the of Schaal oven test results, it was noted that in the fully refined rapeseed, sunflower, and soybean oils, their primary and secondary oxidation products tended to quicker increase their contents compared to the cold pressed oils. The course of the oxidation curves was similar in all the oils examined. However, the rate of oxidation changes was diversified: it was the lowest in the olive oil and the highest in the sunflower oil.
cold pressed oils, refined oils, oxidative stability, Rancimat test, Schaal oven test, rapeseed oil, soybean oil, sunflower oil, olive oil