Publication no. C-1998-1006-03R |  VIEW ARTICLE

Structural Variation and Levels of Water-Extractable Arabinogalactan-Peptide in European Wheat Flours.

A. Loosveld (1,2), C. Maes (1), W. H. M. van Casteren (3), H. A. Schols (3), P. J. Grobet (4), and J. A. Delcour (1). (1) Katholieke Universiteit Leuven, Laboratory of Food Chemistry, Kardinaal Mercierlaan 92, B-3001 Heverlee, Belgium. (2) Corresponding author. E-mail: <annemie.loosveld@agr.kuleuven.ac.be> (3) Department of Food Science, Wageningen Agricultural University, P.O. Box 6700 EV, Wageningen, The Netherlands. (4) Center for Surface Chemistry and Catalysis, Kardinaal Mercierlaan 92, B-3001 Heverlee, Belgium. Cereal Chem. 75(6):815-819. Accepted July 13, 1998. Copyright 1998 American Association of Cereal Chemists, Inc.

Water-extractable arabinogalactan-peptides (WE-AGP) were isolated from flour of eight different wheat cultivars (harvest year 1996). Little structural variation in WE-AGP of flour of the different wheat cultivars was observed. The arabinose-to-galactose (A/G) ratio of WE-AGP varied between 0.66 and 0.73. Methylation analysis showed that the proportion of beta-1,3-galactopyranosyl residues is almost equal for the different WE-AGP samples (10.2-11.1%). More variation was observed for the proportion of the beta-1,6-galactopyranosyl residues (9.4-13.0%) and beta-1,3,6-galactopyranosyl residues (76.0-80.1%). The (^1)H-nuclear magnetic resonance spectra (D(2)O, 85°C, 300 MHz) were comparable, and gel permeation analysis consistently yielded a narrow peak with an apparent molecular weight between 5.0 × 10(^4) and 10.0 × 10(^4). Interpretation of the results was facilitated by alpha-L-arabinofuranosidase debranching of WE-AGP. For flour samples of 18 wheat cultivars (10 from 1994 harvest, eight from 1996 harvest), the variation in percentage of water-extractable arabinoxylan (WE-AX) (0.31-0.78% of dry matter) was much larger than the variation in percentage of water-extractable arabinogalactan (WE-AG) (0.24-0.33%). The ratio of WE-AX to WE-AG for flour samples of different wheat cultivars varied between 1.00 and 2.44.