Abstract
Defatted rice bran treated using subcritical water at temperatures between 150 and 180℃ for 10 min was further treated under subcritical condition at 250℃ for 5 min. The bran extracts obtained from the first-step treatment were evaluated on their emulsifying and emulsion-stabilizing activities by the Pearce and Kinsella method and spectrophotometry at 500 nm. The emulsifying activity of the bran extracts was not dependent upon the first-step treatment temperature. The bran extracts performed equally well in stabilizing emulsions through the test storage period. The antioxidative ability of the bran extracts from each series of the two-step subcritical water treatment was assessed by measuring the induction period and also by monitoring the pressure drop in the closed bottle where oxidation took place. The oxidation was better suppressed in samples added with greater amount of bran extracts. The suppression of coloration of bran extracts by two-step treatment was studied. The bran extracts from the first-step treatment showed high emulsion-stabilizing activity, while the subsequent treatment yielded extracts with a radical scavenging activity comparable to that of the control bran extract obtained from a single-step treatment at 250℃. The two-step subcritical water treatment of defatted rice bran produced higher overall yields compared to the single-step treatment, but showed no noticeable influence upon suppression of coloration in the bran extracts.
