TOTAL AND EXTRACTABLE BETA-GLUCAN CONTENTS OF OATS AND THEIR RELATIONSHIP TO VISCOSITY

Two diverse collections of oats were used to determine the relationships between viscosity and total groat β-glucan. The first collection contained 19 genotypes of oats ranging in acid extract-viscosity (AEV) values from 3·4 to 14·4 centiStokes (cS), total β-glucan 1·8 to 2·8 %, pentosans 2·4 to 4·5% and starch 49·0 to 75·2%. The acid buffer (pH 1·5) extracted, on average, 70% of the total β-glucan, 22 % of the pentosans and < 1 % of the starch. The correlations (r) between AEV and total β-glucan was 0·43 (P < 0·05). In the second collection containing 101 genotypes of oats the correlation between AEV and groat β-glucan content was even lower (0·27; P < 0·01). Twelve genotypes of oats, obtained from the second collection, were extracted with acid buffer and water at pH 6·0 and 10·0. Acid buffer and water (pH 10·0) extracts generally had similar mean viscosities (14·4 and 18·2 cS) and extractable β-glucan (1·1 and 1·2%); the latter formed 23 and 26% of the total β-glucan. However, oats extracted with water at pH 6·0 had low mean viscosity (4·0 cS) but a high mean extractable β-glucan (1·8%), which formed 39% of the total β-glucan, AEV was a poor indicator of total β-glucan content in oats. Second, pH of extraction influenced both the viscosity and extractable β-glucan content of oats. © 1992, Academic Press Limited. All rights reserved.