| Abstract: | Water‐extractable (WE) material was isolated from a Canadian barley malt (cv. Harrington). The purified WE material contained mainly arabinoxylans, β‐glucans, proteins, and small amounts of arabinogalactans and mannose‐containing polymers. WE material was treated with specific enzymes to obtain two fractions: one enriched in arabinoxylan (AX) and another enriched in β‐glucan (BG). The AX fraction was further fractionated by stepwise precipitation in (NH4)2SO4 into five arabinoxylan subfractions. 1H‐NMR spectroscopy and sugar analyses revealed a relatively high content of unsubstituted xylose residues (48–58%) as well as a relatively high content of doubly substituted xylose residues (28–33%) in the structure of the arabinoxylans. β‐Glucans constituted a minor portion of water‐extractable malt polysaccharides and were characterized by high levels of tri‐ and tetrasaccharide residues (93.4%) with a molar ratio of 2.19 for cellotriosyl to cellotetraosyl units. Size‐exclusion chromatography revealed that the WE material contained several polymer populations. One population had a very high molecular weight that appeared to be the result of aggregation. The AX fraction contained higher molecular weight polymers than the BG fraction. |
