Small angle X-ray scattering of resistant starch type III.

Starch fraction, which is resistant to enzymatic digestion, is produced during retrogradation. This fraction, termed resistant starch type III (RSIII), has health benefits such as pre-biotic effects, improving lipid and cholesterol metabolism, and reducing the risk of colon cancer. The work presented in this paper is aimed at investigating the colloidal structure of native high amylose corn starch (HACS) and the RSIII polymorphs produced from it using small angle X-ray scattering. Experimental scattering curves were fitted with appropriate theoretical models such as the "modified lamellar model". Our results show that retrogradation at low temperature leads to formation of polymorph B with crystallinity much lower than that of the granular form, but the lamellas are arranged in long-range periodicity. Conversely, retrogradation at high temperature leads to formation of polymorphs A and V with no defined periodicity. The degree of crystallinity is very low, and the system is better described as a dilute particulate system.