Effect of heating on disposal point of main edible oils available in Iran market

Deep frying is the most common method used for food preparation worldwide, which can lead to several chemical changes in used fat or oil in frying process including oxidation and polymerization. This study aimed to determine the effect of heating and different storage conditions on the disposal point of four types of the most common edible oils available in the Iranian market without and with the presence of food in terms of acid value (AV) and total polar compounds (TPC). AV and TPC of three types of marketed sunflower oil (especially for frying, cooking, solid vegetable) and ghee heated at 110, 150, 180, and 200°C with a portable oil meter DOM‐24 (ATAGO, Japan) were determined. They were measured without the presence of food at four different temperatures and four different times in five storage conditions and with the presence of frying food (chicken and potatoes) at 110°C for 20 min in three replicates. The results showed that the AV and TPC contents in the case of ghee were above national and international standards without the presence of food. Also, in the process of frying chicken and potato, the reusability of all the studied oils was not possible for the second time and reached the disposal point. The increase in the rate of AV and TPC of oils was: ghee (Kermanshahi oil) > liquid cooking oil > frying oil ≥ solid vegetable oil. TPC and AV exceeding rejection limit after one time repeated frying of food. The best desirable conditions for the storage of oils are storing in closed containers at 4C. Stability rate to food frying is: Ghee oil Cooking liquid oil Frying oil Solid vegetable oil.