Distilled water was used as the solvent for aqueous extraction.
N-Hexane was used as the organic solvent. Full fat rice bran, type
Tarom Mahali (10 kg of raw and 3 kg of parboiled) used for experiments
was obtained from the local rice mills. Also, a pH–meter
(Ion Analyzer 250, Corning) was used to read a pH of the solutions.
The pH of the solutions was controlled by adding NaOH or HCl.
Fresh rice bran was screened to pass through a 710 lm aperture
sieve to remove broken grains, hull fragments, paddy kernels and
foreign materials. Rice bran was stored in plastic bags in refrigerator
at 0 C on the day before use to control the growth of rice bran
free fatty acid. To study effect parboiling of paddy on hexane and
ultrasound-assisted aqueous extraction, paddy is parboiled by
soaking in cold water for 72 h followed by steaming for 10 min.
The steamed paddy is then solar dried and milled to remove the
husk.
Free fatty acid (FFA) content of ultrasound-assisted aqueous
and hexane extracted rice bran oil was determined the day after
extraction and then periodically by a micro method. Phenolphthalein was used as indicator in
this titration and FFA content was calculated as oleic acid and
expressed as percent of oil.