Structure-function relationships in A and B granules from wheat starches of similar amylose content
No Thumbnail Available
Date
2009-02-11
Journal Title
Journal ISSN
Volume Title
Publisher
Elsevier
Abstract
Five wheat (Triticum aestivum L.) starches, from the varieties Sunco, Sunsoft, SM1118. and SM1028, with similar amylose content, and a waxy wheat were separated into large (A) and small (B) granules. The unfractionated starches, and isolated A and B granules, were characterized structurally and evaluated for their functional properties. The amylopectin chain length distribution revealed that A granules had a lower proportion of short chains with degree of polymerization (DP) 6-12 and a higher proportion of chains with DP 25-36 than B granules. X-ray diffraction (XRD) patterns showed predominantly A-type crystallinity for all of the starches. No differences in the crystallinity were found between unfractionated, A and B granules. Small-angle X-ray scattering (SAXS) patterns of the starches at 55% hydration showed that the lamellar repeat distance in A granules was larger than that of B granules for all the starches examined. However, the lamellar distances of both A and B granules from the waxy wheat were smaller than those of Sunco, Sunsoft, SM1118 and SM1028 starches. The swelling power of the B granules was greater than that of A granules from all five starches. The kinetics of digestion of A and B granules with α-amylase in vitro were complex, with B granules initially digested to a greater extent than A granules. After 4 h of incubation, A granules showed greater digestibility than B granules, except in the case of waxy starch where unfractionated and fractionated granules had similar in vitro digestibility. Correlations between structural and functional parameters were more significant for the isolated A and B granules than for the unfractionated starches. This study demonstrates that A and B granules differ in structure and functionality, and that some correlations between these properties could be masked in unfractionated starches with bimodal granule size distribution. © 2008, Elsevier Ltd.
Description
Keywords
Small angle scattering, Wheat, Starch, Amylase, X-ray diffraction, Digestion
Citation
Salman, H., Blazek, J., Lopez-Rubio, A., Gilbert, E. P., Hanley, T., & Copeland, L. (2009). Structure-function relationships in A and B granules from wheat starches of similar amylose content. Carbohydrate Polymers, 75(3), 420-427. doi:10.1016/j.carbpol.2008.08.001