Proximate Composition and In-vitro Digestibility Kinetics of Resistant Starches from Bambara Groundnut and Pearl Millet: Effects of Acetylation

Abstract

This study examined the proximate composition and in-vitro digestibility kinetics of resistant starches (RS) from Bambara groundnut (BG) and Pearl millet (PM), with emphasis on the effect of acetylation. Unmodified BG starch retained higher levels of protein, fat, and fiber than its modified counterpart, but unexpectedly lost RS after acetylation. This reduction was attributed to crystalline destabilization and amylose-induced structural disruption. By contrast, acetylated PM starch showed the anticipated increase in RS, accompanied by only moderate declines in protein and minerals, while maintaining overall structural integrity. Digestibility trends confirmed that acetylation produced divergent outcomes between the two crops: BG became less resistant, while PM gained functional starch fractions. In conclusion, acetylation did not uniformly enhance RS content across starch sources. The counterintuitive decline in BG contrasts with the improved RS observed in PM, underscoring the importance of source-specific modification strategies. These findings highlight PM as a more promising candidate for developing low-glycemic, diabetic-friendly foods and functional food formulations, while also indicating that BG may require alternative modification approaches to achieve similar nutritional benefits.