Comparison of antioxidative effects of methanol orange peel extract and butylatedhydroxytoluene on stability of crude peanut oil

Abstract

The antioxidative effects of methanol orange peel extract (MOPE) and butylatedhydroxytoluene (BHT) on stability of crude peanut oil (CPO) stored for twelve months in white transparent plastic bottles at room temperature (27–33 °C) were investigated. Extract of orange peel was prepared by dissolving 20 g of dried, ground and sieved sweet orange peel into 200 ml of methanol for three days. The methanol orange peel extract (MOPE) was added at varying concentrations (200–1000 ppm) to CPO. Another set of CPO which contained 200 ppm BHT as well as CPO that contained no additive was also set up. The colour and refractive indices of oil samples were immediately determined while free fatty acid (FFA), acid value (AV) and peroxide value (PV) of CPO samples were determined monthly using standard methods. The colour of CPO containing additives (MOPE and BHT) and that which contained no additive (0 ppm) was 30.0 units in 1/2′′ cell. The refractive index of CPO containing varying concentrations of MOPE ranged between 1.464 and 1.465 while CPO containing no additive (0 ppm) and 200 ppm BHT was 1.463. There was no significant difference at P<0.05 in FFA, AV and PV of CPO containing MOPE, BHT and CPO containing no additive. The FFA, AV and PV of CPO containing additive (MOPE and BHT) were lower than that of CPO containing no additive. BHT was better in stabilizing hydrolytic rancidity of CPO while MOPE was superior to BHT in stabilizing CPO against oxidative rancidity.