Extraction of γ-oryzanol and proteins from raw and de-oiled rice bran using subcritical and supercritical fluids

Abstract

Subcritical and supercritical fluid extractions have been developed in order to recover valuable compounds from lignocellulosic biomass. In this work, the authors focused on γ-oryzanol and proteins extraction from rice bran and de-oiled rice bran which are generally used as an animal feed. The experimental results showed that supercritical carbon dioxide (SC-CO₂) could be used to extract rice bran oil with relatively high γ-oryzanol concentration whilst subcritical water (SW) could recover 100% of protein. The kinetic information of rice bran protein hydrolysis under SW atmosphere indicated that proteins/polypeptides hydrolyze to amino acids within two pathways. Moreover, the increase in temperature and reaction time (over 200 ℃ and 30 min) favored the proteins/polypeptides degradation rate. Thus, the extraction condition for SW extraction should be optimized or the amino acid production would be focused instead. Finally, the multi-fluid processing or consecutive extraction process using SC-CO₂followed by SW was investigated. The suitable condition obtained from each single-fluid extraction was used. The results showed that SC-CO₂ extraction and SW extraction could be operated sequentially without any interaction. The obtained products were not only rice bran oil with high concentrated γ-oryzanol and proteins, but also sugars, amino acids and other value-added products.