Effects of extracts of Thompson orange peels on the stability of canola oil

ABSTRACT: Oxidation of fats results in a reduction in organoleptic features and in nutritional quality of oils. There are various methods, including the use of antioxidants, to prevent oxidation of oils and to increase their stability. Nowadays, because of the adverse side effects of synthetic antioxidants on man, such as mutagenesis and carcinogenesis, their use has been limited, while the application of natural antioxidants has been on the rise. In this research, the effects of extracts of Thompson orange peels, as a natural antioxidant, on the stability of canola oil were studied and compared with the effects of the synthetic antioxidant Tert-Butylhydroquinone (TBHQ). To this end, the antioxidants of orange peels were extracted by using the solvent methanol, and the total content of phenolic compounds present was determined using the Folin–Ciocalteu method. The effects of different concentrations of extracts in delaying oxidative rancidity in canola oil were studied through calculating the peroxide index and the oil stability test (Rancimat); and these effects were then compared with those of the synthetic antioxidant TBHQ. Results obtained showed that, compared with synthetic antioxidants, high concentrations of extracts of orange peels significantly increased (P < 1%) canola oil stability. According to the stability indices evaluated, orange peel extracts at concentrations of 2000 and 3000 ppm were more effective than the 1000 ppm concentration of this extract in stabilizing canola oil. This increased effectiveness could be attributed to the higher content of phenolic compounds in the 2000 and 3000 ppm concentrations .The effect of this extract in stabilizing canola oil was similar and comparable to that of commonly used synthetic antioxidants (as confirmed by the results obtained from the two peroxide indices and from the oxidative stability indices).