Fig. 6 shows free fatty acid (FFA) content of ultrasound-assisted
aqueous and hexane extracted rice bran oil. As, shown, ultrasoundassisted
aqueous extracted oil has very low FFA (%), this is due to
the fact that FFA content in the bran is saponified with added base
during the extraction process.
Visible absorption spectrums for the estimation of the color of
oil were studied (Not shown). Results showed that ultrasoundassisted
aqueous-extracted oil had a lower content of coloring substances
when compared with hexane extracted oil. This indicates
that less bleaching earth will be needed to refine the oil. Juliano
(Juliano, 1985) reported that carotene and, in the darker oils,
chlorophyll were the main pigments.