Wheat bran arabinoxylans: Chemical structure and film properties of three isolated fractions

The purpose of this study was to isolate arabinoxylans (AX) from wheat bran in order to further investigate the impact of their composition and structure on several physico-chemical properties used for food packaging films. Three hemicellulose fractions were alkali-extracted from destarched wheat bran and fractionated according to their solubility. Moreover, AX were further purified by elimination of beta-glucans. The three AX fractions displayed a wide range of Ara/Xyl ratios varying from 0.2 to 1.3, contained various patterns of arabinose substitutions and different molar mass (152000-218000 Da). The crystalline morphology, the beta transitions and water sorption properties of AX-based films were well correlated with the Ara/Xyl ratios of xylans. When arabinose content decreased, the films were more crystalline and the beta transitions decreased as well as the water uptake at high relative humidity. The local chain motion decreased in the amorphous parts for highly substituted xylans. Furthermore, the presence of co-extracted beta-glucans modified the properties of the AX-films. (C) 2011 Elsevier Ltd. All rights reserved.