Optimization of extraction technique of polyphenols from maize bran and its antioxidant activity

In order to optimize the extraction technique of polyphenols from maize bran by enzymatic extraction, and to investigate the antioxidant properties of the products, the effect of ultrasonic time, extraction temperature, liquid to solid ratio and enzyme dosage were investigated and the extraction amount of polyphenol from maize bran was used as the response value. Based on the single factor experimental analysis, Central Composite Design of response surface analysis was applied to optimize the extraction process. The results showed that the optimal extraction conditions were ultrasonic time 6.5 min, enzymolysis temperature of 55℃, liquid to material ratio of 41 mL · g^-1 and the addition of xylanase 2.10%. Under these conditions, the highest yield of polyphenols was 7.26 ± 0.15 mg · g^-1, which was similar to the predicted value of 7.17 mg · g^-1. The antioxidant tests by DPPH · and ABTS⁺ · scavenging methods showed that polyphenols of maize bran had strong antioxidant capacity, and can be used as potential natural antioxidants in the food industry. These results provided theoretical basis for the comprehensive application of maize bran. (authors)