In vitro digestibility of hydrothermally modified Bambara groundnut (Vigna subterranean L.) starch and flour

In-vitro digestibility and functional properties of Bambara groundnut (Vigna subterranean) (BG) flour, and its native and hydrothermally modified starches were investigated. The isolated native starch (BNS) was modified by annealing at 50 degrees C for 48hr (BAS), and heat-moisture treated at 100 degrees C for 16hr at 25% moisture level (BHS). The crude protein of BG flour was 16.88%. The amylose content of the flour and native starch was 6.10% and 27.70%, respectively. Hydrothermal modification increased the gelatinization profile of the starch but reduces its pasting properties. Swelling and solubility of the flour and starches increased with increase in temperature. X-ray diffraction revealed BNS and BAS exhibited Type C crystallinity pattern while BHS was Type A. The BNS granule was oval, its diameter between 22 and 30m, with no significant change in the morphology of BAS and BHS. The BG flour had 33% resistant starch and 11.63% digestible starch. Heat-moisture treatment enhanced the resistant starch content of the native starch significantly.