A Role of Tocopherol on the Heat Stability of Vegetable Oils

Abstract

Refined vegetable oils (soybean, corn, high oleic safflower and olive oils), tocopherol (Toc) -free and Toc-rich soybean oils were heated in a glass tube for AOM test at 180°C for 10 to 25 hours, respectively, and oxidative stability of these oils with or without Toc after heating was investigated successively by both weighing method and oven test. The oxidative stabilities of the oils were decreased heating, as the result of Toc degradation. However, the oxidative stabilities were increased by the addition of Toc to the heated oils. The oxidative stabilities of olive oil and high oleic safflower oil were especially increased by the addition, whereas those of soybean oil and corn oil were not. The stability of Toc-free soybean oil was markedly low. When olive oils was heated at 180°C for 10 and 17 hours, the residual ratio of Toc was higher in the presence of phosphoric acid and lecithin than in the absence of them. Consequeatly, the oxidative stability of the oil was considerably improved with the additions.