Production Optimization of the Extract with High Phenolic Content and Radical Scavenging Activity from Defatted Rice Bran by Subcritical Water Treatment

The optimum conditions for subcritical water treatment to produce an extract with a high phenolic content and radical scavenging activity from defatted rice bran were determined using response surface methodology. The effects of the weight ratio of bran to water from 0.05 to 0.2 and treatment time from 20 to 120 min on the total phenolic content and DPPH radical scavenging activity were evaluated using the Design-Expert program. Both the total phenolic content and DPPH radical scavenging activity increased with an increase in the bran/water ratio, but decreased with the treatment time. The optimum bran/water ratio and treatment time were 0.2 and 20 min, respectively, to attain a relatively highest total phenolic content and DPPH radical scavenging activity.