Material and rheological properties of native, acetylated, and pregelatinized forms of corn, cassava, and sweet potato starches

The effects of acetylation and pregelatinization on the material and rheological properties of selected botanical starches as pharmaceutical excipients were evaluated. Pregelatinized and acetylated forms of starches of cassava, Manihot esculenta Crantz (Euphorbiaceae) and sweet potato, Ipomoea batatas L. Lam (Convolvulaceae) were prepared and corn starch BP was the standard. The starches were evaluated using physicochemical, microscopic, rheological, FTIR, and X-ray diffraction (XRD) analytical techniques. Microscopic analysis indicated definitive alteration in the granular character of the modified starches. The native starches were susceptible to retrogradation, which was alleviated by acetylation and pregelatinization. Flowability of the starches improved with modification while FTIR and XRD analysis confirmed characteristic functional groups and crystalline morphology of the modified starches. The water absorption and swelling properties of the starches were related to amylose content. Acetylation and pregelatinization of cassava and sweet potato starches significantly altered their granular morphology, rheology, and structure resulting in their improved functionality as potential pharmaceutical excipients.