CEREAL ARABINOXYLANS - ADVANCES IN STRUCTURE AND PHYSICOCHEMICAL PROPERTIES

Arabinoxylans constitute a major fraction of cereal cell wall polysacc harides. They consist of a linear beta-(1-->4) linked xylan backbone t o which alpha-L-arabinofuranose units are attached as side residues vi a alpha-(1-->3) and/or alpha-(1-->2) linkages. Several structural mode ls have been put forward based on enzymic degradation studies and stru cture elucidation of oligosaccharides by NMR, methylation, and perioda te oxidation techniques. These tentative models present different subs titution patterns of arabinoses along the xylan chain. Cereal arabinox ylans exhibit a great deal of structural heterogeneity with respect to ratio of Araf/Xylp, substitution pattern of arabinoses, content of fe ruloyl groups and molecular size. The conformation and physicochemical properties (viscosity, gelation potential, intermolecular association ) of arabinoxylans in aqueous solutions are dependent on the molecular features of these polysaccharides; specific structure-property relati onships have been established in model and actual food systems. Wheat and rye arabinoxylans are important functional ingredients in baked pr oducts affecting the mechanical properties of dough, as well as the te xture and other end-product quality characteristics.