Abstract
The autoxidative and thermal oxidative stabilities of oils mixed in various ratios were investigated. Vegetable oils (rape seed, soybean, palm, hardened soybean, cotton seed, safflower, high oleic safflower, sesame seed and olive oils) and their blend oils were oxidized in a beaker (4×5.5cm; oils, 10g) at 60°C, or heated in a glass tube (2.7×20cm; oils, 10g) at 180°C, and then the peroxide, anisidine and carbonyl values were measured. The autoxidative and thermal oxidative stabilities of soybean and rape seed oils were greatly increased by blending with palm oil. On the other hand, the extent of the thermal decomposition of tocopherol (Toc) in oils was increased by increasing the quantity of palm oil. Sesame seed oil and a mixture of soybean and sesame seed oils showed the highest stability against thermal oxidation, and moreover, the addition of sesame seed oil suppressed the thermal decomposition of Toc in oils. The most suitable blend ratios for thermal oxidative stability of oils were found to be as follows: The ratios between rape seed and palm oils, soybean and palm oils, hardened soybean and palm oils, cotton seed and olive oils, safflower and high oleic safflower oils, corn and hardened soybean oils, soybean and sesame seed oils were all 2: 8. The ratio between soybean and cotton seed oils was 6: 4, and that between soybean, rape seed and palm oils was 3: 3: 4.
