Structural and morphological factors influencing the quantification of resistant starch II in starches of different botanical origin

Seven cereal starches and 11 pea starches were analysed for total starch, amylose content, resistant starch type II (RS), total dietary fibre (TDF) and starch damage. The data from the cereal starches could be interpreted on basis of the already published polymorph type. In the pea starch series RS and TDF correlated with the amylose content for most starches. But one starch with 20.7% of amylose had an extraordinary high RS content of 16.8%. DSC thermograms, starch granule size distribution, scanning electron and light micrographs revealed a large fraction of small granules of high cristallinity and high α-amylase resistance. Another starch of 32% amylose had a very low RS content. The reason for this was a high fraction of large starch granules, some being damaged. This study shows that besides amylose content, granule morphology and size, its extent of crystallinity or damage have a strong impact on the amylase resistance.