Publication no. C-2002-0401-07R |  VIEW ARTICLE

Structural Characteristics of Water-Extractable Nonstarch Polysaccharides from Barley Malt (1).

M. Cyran (2), M. S. Izydorczyk (3,4), and A. W. MacGregor (3). (1) Contribution No. 824 of the Grain Research Laboratory, Canadian Grain Com­mission, 1404-303 Main Street, Winnipeg, Manitoba R3C 3G8, Canada. (2) Department of Nutritional Evaluation of Plant Materials, Institute of Plant Breed­ing, Radzikow, 05-870 Blonie, Poland. (3) Grain Research Laboratory, 1404-303 Main Street, Winnipeg, Manitoba, R3C 3G8 Canada. (4) Corresponding author. E-mail: <mizydorczyk@cgc.ca> Phone: 204-983-1300. Fax: 204-983-0724. Cereal Chem. 79(3):359-366. Accepted December 5, 2001. Copyright 2002 American Association of Cereal Chemists, Inc.

Water-extractable (WE) material was isolated from a Canadian barley malt (cv. Harrington). The purified WE material contained mainly arabin­oxylans, beta-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 beta-glucan (BG). The AX fraction was further frac­tionated by stepwise precipitation in (NH(4))(2)SO(4) into five arabinoxylan subfractions. (^1)H-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. beta-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.