SUPRAMOLECULAR STRUCTURE OF LEGUME STARCHES REVEALED BY X-RAY-SCATTERING

The X‐ray wide‐angle scattering patterns of legume starches are attributed to the C‐type in contrast to the A‐ and B‐type of cereal and root starches. Starting from the question if this C‐pattern is to be considered as a mixed A‐ and B‐type or as an independent X‐ray wide‐angle diffractogram. examinations have been performed with starches from Vicia faba and Pisum sativum in comparison with pure A‐ and B‐type starches from maize and potato. The phase proportions in the crystalline parts of the C‐starches were calculated by means of a linear regression method. The pea starch is composed of 38.6% type B and 61.4% type A, and for the starch of bean we calculated 17.0% type B and 83.0% type A. By these results as well as by the high values for the correlation coefficients it is proved that the starch C‐polymorph is a mixture of A‐ and B‐unit cells. The legume starches consist of starch granules of pure A‐type as well as of pure B‐type in varying relations. Copyright © 1990 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim