ANALYSIS OF THE FORCED OXIDABILITY OF GRAPE SEED, WALNUT AND CORN OILS

Abstract

Lipid oxidation is one of the major causes of decreased nutritional value of foods, limiting their shelf life. This phenomenon leads to the formation of oxidative degradation products, which essentially change the nutritional and organoleptic qualities of the products. However, even worse is the fact that the consumption of metabolites of oxidative degradation of lipids is the cause of oxidative stress of the human body and, respectively, causes multiple morbid conditions of the human health. A study on the process of forced oxidation of grape seed oils, walnuts and corn in the presence of hydrogen peroxide and Cu (II) ions was realized. The thermo-oxidation of the oil caused a significant decrease in the saponification index, which indicates a significant degree of polymerization and leads to an increase in the viscosity of the studied sunflower oil. To highlight the impact of heat treatments, the analysis was performed by IR spectroscopy and the possible mechanisms of forced oxidation of unsaturated fatty acids under the influence of heat factor were analyzed. It was established that the applied treatment favored both the formation of carbonyl secondary compounds and the simultaneous formation of hydroperoxides and triglycerides containing hydroxylated groups. The accumulation of hydroperoxides and triacylglycerides that have hydroxyl functions have facilitated the course of polymerization reactions, which are to increase the viscosity of the studied thermo-oxidized sunflower oil. Analogous to the forced oxidation of sunflower oil, the formation during oxidation of trans-isomers of polyunsaturated acids was attested. The study investigated and identified the minimum concentrations of antioxidants needed to reduce the oxidation of the analysed oils.