Enhanced antioxidant activity of rice bran extract by carbohydrase treatment

Rice bran (RB) was treated with different carbohydrases (Viscozyme, Termamyl, Celluclast, AMG, Ultraflo, and Pentopan), and then aqueous alcoholic extracts (50% ethanol) from the treated RB were examined for their phenolic compositions and antioxidant activities (radical scavenging activity and ferrous reducing activity). All the carbohydrases tested induced significant increases in ferric reducing power (1.5-3.3 times). Among the enzymes tested, Pentopan which was active in pentosan hydrolysis appeared to be most effective in increasing the antioxidant activity. Celluclast, Ultraflo, and Pentopan appeared more effective in increasing the total phenolic content (TPC) as well as radical scavenging activity than other enzymes. These enzymes increased the amount of extractable phenolic acids by 2.5-3.0 times, especially for ferulic, p-coumaric, vanillic, and p-hydroxybenzoic acids. Enzymatic hydrolysis of cell wall polysaccharides in RB could be used as an effective procedure for raising the amount of extractable phenolic acids and thus increasing the antioxidant activity of RB extract.