Comparative study of oxidatuve stability of different vegetable oils by the rancimat method and oven test

Oksidacija lipida je prepoznata kao glavni problem u jestivim uljima, ona prouzrokuje važnu promjenu kemijskih, senzorskih i nutritivnih svojstava. Oksidacijska stabilnost različitih biljnih ulja istraživana je primjenom Rancimat metode baziranoj na konduktometrijskom mjerenju i Oven testom (63 oC) baziranom na određivanju peroksidnog broja. Ispitivanja su provedena sa različitim biljnim uljima: suncokretovo ulje, visokooleinsko suncokretovo ulje, bademovo ulje, ulje pšeničnih klica, ulje šafranike i orahovo ulje. Oksidacija ulja inducirana je i mjerena primjenom Rancimat uređaja (uzorak 3,0 g, temperatura 120 oC, protok zraka 9 L/h). Rezultat oksidacije ulja izražen je sa indukcijskim periodom (IP). Stabilnost ulja proporcionalna je indukcijskom periodu. Rezultati mjerenja dobiveni Rancimat metodom podudaraju se sa onim baziranim na klasičnoj titraciji Oven testom. Primjenom ovih metoda za praćenje stabilnosti biljnih ulja vidljivo je da visokooleinsko suncokretovo ulje ima najbolju stabilnost prema oksidaciji upravo zbog visokog udjela oleinske kiseline, a orahovo ulje ostvaruje najmanju stabilnost.Lipid oxidation has been recognized as the major problem affecting edible oils, as it is the cause of important deteriorative changes in their chemical, sensory and nutritional properties. The oxidative stability of different vegetable oils was studied using the Rancimat method based on conductometric measurements and Oven test (63 oC) method based on determination of peroxide value. Different vegetable oil samples were used in this study: sunflower oil, high oleic sunflower oil, almond oil, wheat germ oil, safflower oil and walnut oil. The oxidation was induced and measured using Rancimat equipment (sample 3.0 g, temperature 120 oC, airflow 9 L/h). The result of oil oxidation was expressed as induction period (IP). Stability is proportional to the induction period. The results obtained by Rancimat method measurements correspond with those based on the classical titration method in Oven test. By using these methods in monitoring stability of vegetable oils, it is visible that high oleic sunflower oil has the best stability toward oxidation exactly because of the high content of oleic acid, whereas walnut oil has the lowest stability