Polymorphism 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. Since RSIII preserves its nutritional functionality during cooking processes, it may be used as a food ingredient. This research is part of a project that explores the relation between the structural properties and prebiotic behavior of RSIII. A procedure was developed for the production of different RSIII polymorphs from the same plant source, and applied to three different native starches. For all three types (high amylose corn starch, wheat starch, cornflour), the polymorph structure was determined by the crystallization temperature. Retrogradation at 40 °C lead to the formation of B-type polymorph, whereas incubation at 95 °C, produced a mixture of A- and V-type polymorphs. Differential scanning calorimetry measurements showed no measurable differences in the melting temperatures between the polymorphs, and exhibit an endothermic transition over the range of T_m = 140-170°C.