Solid state characterization and rheological properties of native and modified Bambara groundnut (Vigna subterranean) starches

This study was designed to determine the suitability of starches from the native, pregelatinized and carboxymethylated Vigna subterranean (Bambara nut) for pharmaceutical applications by physicochemical, rheological, thermal, morphological and instrumental spectroscopic methods. The native starch was extracted from the Bambara nut, after which it was prepares in both pregelatinized and carboxymethylated forms. Microscopy revealed increased granular size after modification. Both pregelatinized and carboxymethylated Bambara starches showed improved flow properties and swellability compared to the native starch. Native Bambara starch had greater tendency to retrogradation, was more sensitive to heat and heat changes, which were reduced by both pregelatinization and carboxymethylation. DSC confirmed that carboxymethylated Bambara starch was the most thermally stable starch. The presence of functional groups and crystallinity were established by FTIR and XRD, respectively. This study shows that native and modified Bambara starches could be used as locally, readily available alternative excipients in pharmaceutical formulations.