Effect of Repeated Heating on The Oxidative Degradation of White Coconut Oil and Soy Bean Oil

Abstract

Repeated heating of cooking oils is a common practice used mainly to save the cost in food preparations. The aim of the present study was to investigative the effect of repeated heating on the oxidative degradation of frying oils (white coconut oil and soy bean oil). Initially, fresh potatoes were peeled off and sliced into uniform thickness (4×0.3×0.3 cm3). Sliced potatoes (batches of 25 g) were fried in 100 mL portions of white coconut oil (WCO) and soy bean oil (SO) separately at 180±5 °C for 10 minutes. The oils were reused for 2 more frying cycles over a span of 3 days (1 frying cycle per day). In each day, an amount of fresh oil was added to make the volume of frying oil in to 100 mL. After each frying cycle, oil samples were collected from the frying pan and by extraction of fat with n-hexane from potato chips. Level of oxidation of frying oils and lipid extracted from potato chips were assessed by measuring the peroxide value (PV) and thiobarbituric acid reactive substances (TBARS). Table 01 states the results of PV and TBARS. Both PV and TBARS of frying oils and lipid extracted from potato chips increased as the number of frying cycles were increased (Table 01). Fried SO (FSO) and lipid extracted from potato chips fried in SO (PSO) showed higher PV and TBARS values than that of fried WCO (FWCO) and lipid extracted from potato chips fried in WCO (PWCO) in every frying cycle (Table 01).