Functional properties of dietary fibre enriched extrudates from barley

Products with new functional and nutritional properties are a precondition for a higher acceptance of barley in human nutrition. Amylose can be partly converted into enzyme-resistant starch (RS) by technological treatments. Optimal conditions for generation of RS from barley using a single-screw laboratory extruder were the following: feed moisture approximately 20%, mass temperature approximately 150 degrees C, screw speed approximately 200 rev/min and a relatively wide die. Extrusion followed by freeze-storage resulted in formation of RS up to 6%. Under these conditions, the macromolecular state of beta-glucan was preserved. Functional and physico-chemical properties of extruded preparations and of their extracts were determined and compared to an autoclaved product. In extracts; high viscosities and a pseudoplastic behaviour were found. Viscosity and flow behaviour were temperature- but not pH-dependent. Water binding properties and the acid-extract viscosity were influenced by process parameters during extrusion. The molecular weights of beta-glucans isolated from extrudates were between 80 000 and 125 000. Extruded products interacted with glycoconjugated bile acids (pH 5.0-6.5). During in vitro fermentation of pancreatin-digested extruded or autoclaved products with human faeces flora, the production of short-chain fatty acids and the molar portion of butyrate were more increased compared with pancreatin-digested barley meal. (C) 2000 Academic Press.