Examining the possibility of improving the properties of sunflower oil in order to obtain a better medium for the process of frying food

With the modern and accelerated way of life, frying has become an extremely common way of food preparation. In the frying process hot oil or fat serves as a heat transfer medium. Ideal fat in all frying processes doesn't exist due to differences in the chemical composition of the product, process conditions, expected nutritive value and shelf life of the final product. During frying, physical and chemical changes simultaneously occur changing the chemical composition of edible oils. The food is immersed in hot fat, in the presence of air, where the frying medium is directly affected by three agents: moisture from the food, atmospheric oxygen and high temperature. Reactions that occur are: hydrolysis, auto-oxidation, thermal oxidation and thermal decomposition, and the products that occur affect various physical and chemical changes in fats, as well as in fryed food. The quality and oxidative stability of vegetable oils or their resistance to changes caused by oxidative processes is the time during which oils can be protected from the (auto)oxidation process. Analytical methods used in practice to determine the oxidative stability of oils are: accelerated oil oxidation test (Rancimat test and OSI index) and Schaal-oven test. In this paper, the possibilities of improving refined sunflower oil in order to obtain oil with greater application in the food frying process are examined. Standard refined sunflower oil, sunflower oil with altered fatty acid composition, as well as sunflower oil enriched with natural and synthetic antioxidants were tested. The obtained results were compared with palmolein, commonly used for food frying. Of the tested sunflower oils, high-oleic sunflower oil with an iodine value (IV) of 85 g/100 g, OSI index of 9.3 and total oxidation (TOTOX) index of 4.73 increased 6.66 times after exposure to frying proved to be the most similar to palmolein (IV=57 g/100g; OSI=17.8; TOTOX=7.60).