Content, structure and viscosity of soluble arabinoxylans in rye grain from several countries
Bengtsson, S. | Andersson, R. | Westerlund, E. | Aman, P.
Rye grains from Finland, Canada, Sweden and Poland were extracted, during starch hydrolysis. A with sodium acetate buffer at 95 degrees C and soluble polymers were isolated by ethanol precipitation. The amount of sugar residues in the isolated polymers varied from 2.3 to 4.1% of rye dry matter with arabinose xylose and glucose residues predominant. High-field 1H-NMR analysis revealed that arabinoxylan I, containing terminal arabinose and un- and mono-substituted xylose residues. and arabinoxylan II, containing terminal arabinose and un- and double-substituted xylose residues, together with mixed-linked (1 leads to 3), (1 leads to 4)-beta-D-glucans, were the dominating features in all samples of soluble polymers. On average, 46% of the xylose residues in arabinoxylan I and 57% in arabinoxylan II were substituted and the degree of substitution in the respective polymers was similar for all samples. The average content of arabinoxylan I ranged from 1.4% in samples from Canada to 1.7% in the Swedish samples and that of arabinoxylan II from 0.6% in samples from Poland to 1.0% in the Canadian samples. The viscosity of the soluble polymers was measured at a shear rate of 100 S-1. It was shown by partial least-squares regression that in these samples the content of structural units characteristic of arabinoxylan II had a stronger correlation to viscosity than those of arabinoxylan I.
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