Degradation of tocopherols in rice bran oil submitted to heating at different temperatures

Abstract

The objective of this study has been to evaluate the stability of α-, (γ+β)-, and δ-tocopherols in rice bran oil chemically refined submitted to heating in a heater without air circulation and shielded from light, at temperatures of 100°C and 180°C. The collection of samples took place after 48, 96, 144, 192, 240, 336, and 432 h of heating and were stored in amber-colored flasks and frozen (-18°C). The analyses of tocopherols took place in accordance with the method by Chen and Bergman (2005), with slight modifications, utilizing a system of high efficiency system of liquid chromatography. It was observed that the α-tocopherol is present at higher concentration in rice bran oil (328.4 mg/kg), followed by (γ+β)-tocopherol (99.1 mg/kg), and δ-tocopherol (7.7 mg/kg). The α-tocopherol in rice bran oil submitted to 100°C showed a reduction of 28.65% at the end of 432 h of heating whereas when submitted to 180°C temperature; its reduction was of 100% at the end of 240 h of heating. The contents of (γ+β)and δ-tocopherol in rice bran oil at the end of 432 h of heating at 100°C was of 79.9 and 6.4 mg/100 g, respectively.