Investigation of peroxidation kinetics of some industrial and kitchen oils

Fats, which constitute an important constituent of a healthy human body, are not only high energy sources, but also contain fat soluble vitamins and combine with proteins to form lipoproteins, and play a role in blood lipid levels. Fats are generally classified according to saturated, unsaturated, cis and trans fatty acid structures and are marketed industrially due to their different fatty acid contents. Many studies in the field of health indicate that unsaturated fatty acids are very valuable, but they are also risky due to their tendency to auto oxidation. Saturated and trans fats affect the physical and sensory properties of the human being with their taste and flavors, but consuming too much has negative effects such as cardiovascular diseases. Otooksidation, which is defined as a natural reaction of lipids and oxygen, is an important event that plays a role in the quality of food, its storage, degradation and development of degenerative diseases. The elucidation of the lipid peroxidation process and the examination of the reaction kinetics will contribute to the shelf-life of the industrial food products and the studies on healthy living. This study was carried out in two steps in order to reveal the relationship between fatty acids and oxidation rates. In the first part, the determination of iodine index of sunflower, corn, olive, rosehip, argan and walnut oils and GC-MS analyzes were performed. In the second section, lipid peroxidation kinetics were examined in the presence of Cu (II) ions at 37 oC and pH 7 in the aerated and incubated oil emulsions. Iron (III) -thiocyanate (Fe (III) SCN) and thiobarbituric acid reactive species (TBARS) methods were used for the examination of primary oxidation products (hydroperoxides) and secondary oxidation products (malondialdehyde), respectively. In both methods, pseudo-first-rate velocity equation was used and velocity constants were found for each oil. As a result, the oxidation rate of the examined oils for primary product formation Walnut oil> Argan oil> Rosehip oil> Sunflower oil> Corn oil> Olive oil; for secondary product formations Walnut oil> Rosehip oil> Argan oil> Olive oil> Sunflower oil> Corn oil followed the order. Key Words: Lipid oxidation, TBARS method, [Fe(III)SCN] method, trans fat, argan oil, GC-MS.