Effects of Wheat Bran Varieties and Extraction Methods on the Structure and Antioxidant Activity of Arabinoxylan

Abstract

Purpose: To compare the structure and antioxidant activity of arabinoxylan (AX) extracted from wheat bran of different varieties by different methods. Methods: AX was extracted from wheat bran from the cultivars ‘Bainong 207’, ‘Baihan 207’, ‘Guanmai 1’, ‘Huayu 198’ and ‘Huayu 166’ by alkali extraction, ultrasonic-assisted xylanase extraction or ultrasonic-assisted cellulase extraction, and its chemical composition, relative molecular mass, molecular structure, thermal stability and antioxidant activity were determined. Results: Among the three extraction methods, alkali extraction gave higher levels of AX yield and total sugar content, while enzymatic extraction retained polyphenols to a greater extent, which may contribute to the better antioxidant capacity of the AX-rich extract, but reduced the relative molecular mass of AX to a certain extent. The monosaccharide composition of enzymatically extracted AX was significantly different from that of alkali extracted AX, and the glycosidic linkage types in enzymatically extracted AX were more complex. Compared with ultrasonic-assisted cellulase extraction, higher AX yield and total sugar content were obtained using ultrasound-assisted xylanase, while the polyphenol content of AX obtained by ultrasound-assisted cellulase extraction was higher, and monosaccharide composition and glycosidic linkage types were also different between AXs extracted by the two enzymatic methods. In addition, the relative molecular mass, the monosaccharide composition, and the types and proportions of glycosidic linkage of AX extracted from wheat bran of different varieties were different. Conclusion: The structure and activity of AX extracted from wheat bran by alkali extraction, ultrasonic-assisted xylanase extraction and ultrasonic-assisted cellulase extraction were obviously different. Compared with alkali extraction, AX obtained by enzymatic extraction had lower yield and molecular mass, but higher polyphenol content and better antioxidant performance. Compared with ultrasound-assisted cellulase extraction, AX obtained by ultrasound-assisted xylanase extraction had higher yield and total sugar content, but lower polyphenol content. The structure of wheat bran AX varied with different extraction methods and varieties.

Keywords

• arabinoxylan; alkali extraction; ultrasound-assisted enzymatic extraction; structural characterization; antioxidant property