The Concentrations of Tocols and gamma-Oryzanol Compounds in Rice Bran Oil Obtained by Fractional Extraction with Supercritical Carbon Dioxide

Abstract

Rice bran oil (RBO) is a good source of several commercially important bioactive phytochemicals, such as tocols (i.e. tocopherols and tocotrienols) and ferulic esters of sterols (i.e. gamma-oryzanol). The aims of the present study were to examine the effects of different pressure and temperature combinations on the fractional extraction of RBO using supercritical carbon dioxide (SC-CO2) and to assess the levels of tocols homologues and gamma-oryzanol components in the resulting oil fractions. Fractional extraction of rice bran oil was performed using SC-CO2 at either 27.6 or 41.4 MPa and either 40 or 60 degrees C. The effects of the four different pressure and temperature combinations on the levels of seven tocols homologues (alpha-, beta-, gamma- and delta-tocopherol and alpha-, gamma- and delta-tocotrienol) and the four major components of gamma-oryzanol in the resulting oil fractions were investigated. Superior extraction efficiency was obtained using the higher pressure of 41.4 MPa. The tocols (particularly a-tocopherol and alpha-tocotrienol) were recovered early in the extraction process, while the gamma-oryzanol compounds were obtained in the later stages. With regard to SC-CO2 extraction, tocols are more soluble than gamma-oryzanol components, alpha-tocopherol is the most soluble of the tocols and the four gamma-oryzanol components all have similar solubilities. Valuable data on solubilities of tocols homologues in SC-CO2 were provided from present study.