Abstract
The Rancimat method (Metrohm Co., Ltd. E 679, Herisan, Switzerland) was employed to determine the oxidative stability of olive, soybean and whale oils. The Rancimat method is based on the conductometric determination of volati le degradation products of oil heated at 120°C with aeration and automatic plotting of the conductivity against time. The evaluation is performed graphically after completion of the experiment. The order of oxidative stability of oils was olive oil (induction time I.T., 6.15h) >soybean oils (I.T., 3.03h) >whale oil (I.T., 0.87 h). The oxidative stability of oils assessed by the Rancimat method and active oxygen method (AOM test), oven test and weighing method showed a good correlation. Peroxide, anisidine, carbonyl and acid values of olive, soybean and whale oils at the rancid point (I.T.) were measured. The peroxide values were not similar among the oils. The anisidine and carbonyl values of both olive and soybean oils were almost the same, while those of whale oil were much lower. On the other hand, the acid value was highest for whale oil. From these results, it appears that the chemical characteristics of oils at the I.T. obtained by the Rancimat method are not similar among oils with different fatty acid compositions.
