Effects of Temperature and Flow Rate on Subcritical-water Extraction from Defatted Rice Bran

The effect of the subcritical water treatment along with the combination of static and dynamic modes on the recovery of protein, carbohydrate and phenolic substances from defatted rice bran was investigated at various treatment temperatures of 120, 160, 200 and 250 degrees C and the flow rates of 0.5, 2.5 and 5 mL/min. The highest amounts of protein and carbohydrate were recovered at 160 degrees C and that of the phenolic substances was recovered at 250 degrees C. Around half of the protein and carbohydrate contents were degraded at 200 and 250 degrees C. The various flow rates from 0.5 to 5 mL/min did not significantly affect the contents of the protein, carbohydrate and phenolic substances recovered from the bran. The extract also had a DPPH radical scavenging activity, which depended on the treatment temperature. While the extract obtained at 120 degrees C at the same flow rate and same amount of water fed to the bran had the lowest radical scavenging activity, the activities in the extracts at 160 - 250 degrees C were around 3 times higher than that at 120 degrees C and there was no significant difference among them.