Effectiveness of the antioxidants BHA and BHT in selected vegetable oils during intermittent heating

Abstract

The heating performance of olive oil was compared with that of corn oil, olive-residue oil and 50:50 mixture of olive oil and corn oil. The oils were heated intermittently for two hours per day at a temperature of 175 ± 5° C for five consecutive days. Under such conditions thermal and oxidative decomposition of the oils takes place. Free fatty acid content, peroxide values, E^1%_{1 cm}, at 232 and 270nm, polar compounds, colour and viscosity, of the oils all increased, whereas the iodine values, smoke points, polyunsaturated fatty acids content and tocopherol concentration decreased. The effectiveness of butylated hydroxyanisole (BHA) and butylated hydroxytoluene (BHT) at a rate of 200 ppm in retarding the deterioration of oils during static heating (175 ± 5° C), was studied and it was found that BHA gave a slight protection to the olive-residue oil and the BHT gave some protection to the corn oil, while both antioxidants were relatively ineffective in the other oils.