Cereal Chem. 70:324-329   |  VIEW ARTICLE

Heterogeneity in the Structure of Water-Soluble Arabinoxylans in European Wheat Flours of Variable Bread-making Quality.

G. Cleemput, S. P. Roels, M. Van Oort, P. J. Grobet, and J. A. Delcour. Copyright 1993 by the American Association of Cereal Chemists, Inc. 

The contents of water-soluble, enzyme-extractable, and total nonstarch polysaccharides (NSPs) were determined in six European wheat flours (Apollo, Slejpner, Sperber, Camp Remy, Minaret, and Soissons) with different mixing time and baking absorption characteristics and, hence, widely varying bread-making capacities. The NSP contents varied between 0.42 and 0.69, 1.20 and 1.73, and 1.35 and 2.25%, respectively. The water-soluble NSPs were extracted and fractionated by ethanol precipitation into arabinoxylans and arabinogalactans. In the arabinoxylan fractions, beta-glucan occurred as a minor contaminant. The L-arabinose to D-xylose ratios of such arabinoxylans varied between 0.51 and 0.61, whereas the ratios of di- to monosubstituted D-xylose residues (estimated by 1H nuclear magnetic resonance) varied between 0.80 and 1.81. A major proportion of the xylan residues (63-66%) were no t substituted by L-arabinose, whereas 13-21% and 16-24% of the D-xyloses were mono- or disubstituted, respectively. From the [1]H nuclear magnetic resonance spectral data, it could be concluded that the disubstituted D-xyloses were either isolated or occurred as pairs in the arabinoxylan chain. Shodex B-806 chromatography yielded, for all arabinoxylan fractions, three peaks with estimated molecular weights between 8.5 X 10[5] and 5 X 10[3], with only the relative proportions of the peaks, but not their molecular weights, varying with the variety. No apparent relationship was found between the molecular weight profiles and the L-arabinose substitution pattern in the arabinoxylans. Correlation coefficients between the analytical data obtained for the NSP content in the six European wheat flours and the baking absorption and mixing time of the corresponding flours increased when the structural variation in the arabinoxylans was taken into account, showing that increased knowledge of the arabinoxylan structure may lead to an enhanced understanding of the role of NSP in breadmaking.