The effect of temperature on rice oil bleaching to reduce oxidation and loss in bioactive compounds

Abstract

Refining conditions are very important to obtain high-quality rice oil. This work aimed at evaluating the effect of bleaching temperature in chemical and physical refining processes to avoid losses in γ-oryzanol and carotenoids. In addition, the aspects related to rancidity were investigated. Samples of degummed oil (obtained by a physical procedure) and of neutralized oil (obtained by a chemical procedure) were provided by a local industry. The oils were bleached at 80, 95 and 110 °C using 1% (w w-1) activated earth. The temperature of 95 °C was the best in relation to oxidative stability. The γ-oryzanol and carotenoids were better preserved through physical refining than by the chemical procedure by about 64 and 84%, respectively. However, the oxidation indicators were high for the oil bleached by the physical procedure, indicating that bleaching without prior neutralization is viable, but it is necessary to obtain an industrial crude oil with less oxidation.