Preparation and analysis of dietary fibre constituents in whole grain from hulled and hull-less barley

Abstract

Sixteen different barley samples (7 of which were hull-less; H-L) were milled and subjected to pre-extraction with ethanol and hexane. Water soluble materials (WSM-TP-AI), containing mostly β-glucans, were purified from the hot water extracts by the use of heat-stable amylase. Crude arabinoxylans were extracted by an alkali solution (WUM-B-S) and purified by the use of β-glucanase and amyloglucosidase, giving AX. Finally insoluble fibre residues were obtained (WUM-B-R). GC and NMR analyses revealed no marked quantitative and qualitative differences of β-glucans or the water-soluble arabinoxylans in WSM-TP-AI between the H-L and the hulled (H) varieties. Significant differences among the two barley types were found in the Ara/Xyl ratio of the starting materials as well as the alkali soluble material (WUM-B-S) and the alkali insoluble residue (WUM-B-R). For alkali soluble AX the H samples had the lowest arabinose content. A single-tube preparative isolation procedure for starch-free barley fibre was used. Combined with NMR and GC this is a tool to produce defined fibre fractions for biological testing.