Nonstarch polysaccharides from preprocessed wheat bran: Carbohydrate analysis and novel rheological properties

Wheat preprocessing technology produces a bran fraction rich in both solubl e (85%) and insoluble (29.2%) fibers. The fraction, prepared by the Tkac an d Timm commercial process, contained 9% alkaline extractable nonstarch poly saccharides (NSP). Conditions for extraction of NSP were chosen on the basi s of both yield and molecular size of product. The extracted NSP was compos ed of an arabinoxylan and a mixed linkage (1-->3)(1-->4)-beta-D-glucan. The NSP differed from previously reported wheat pentosans by exhibiting shear- thinning flow behavior at low concentration in water (0.5%, 25 degrees C) a nd, more importantly, forming a thermally reversible gel upon cooling at 4 degrees C. This unique gelling property is neither the commonly described i rreversible gelation brought about by oxidation of wheat endosperm pentosan s nor a characteristic property of cereal beta-glucan. The low degree of su bstitution of the xylan chain of the arabinoxylan (xylose-to-arabinose rati o = 3) in this NSP might be responsible for the rheological behavior.