Rice bran obtained from a local milling
factory was processed into two steps: defatting
and protein extraction. The defatting procedures
employed are according to Wang et al. (1999).
Briefly, rice bran is defatted twice using hexane in
bran to solvent ratio of 1:3 at a setting of 250 rpm
in a lab stirrer for 30 min and centrifuge at 5000 g
for 10 min. at room temperature (RT). The defatted
rice bran (DRB) is air-dried overnight, sieved
through a 100 mesh screen, packed in a bag and
stored at 5ºC. The extraction step is a modification
of Gnanasambandam and Hettiarachchy, 1995:
alkaline extraction followed by isoelectric precipitation
are used to prepare rice bran extract. The
process is described as follows; Defatted rice bran
sample and distilled deionized water (1:4) was pH
adjusted to 9.5 and stirred 30 min at room temperature
(RT). The slurry was centrifuged (Sorvall®
RC 28 S) at 5000 g for 30 min. (RT). The pH of
supernatant was adjusted to 4.5 and centrifuged
again at 5000 g for 30 min. (RT). Precipitate was
washed using water (pH 4.5). The residue was
suspended in distilled deionized water (pH 7.0)
and frozen overnight. The final product, which is
called rice bran protein concentrate (RBPC), was
then freeze dried (Freeze dryer, Flexi-Dry μP FTS
™system) and stored at -5 ºC.