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

Optimisation of the techno-functional and thermal properties of heat moisture treated Bambara groundnut starch using response surface methodology

This work optimised the techno-functional and thermal properties of heat moisture treated Bambara groundnut starch (BGS). A central composite rotatable design (Design-Expert software v8.0.1.0) comprising two independent factors of temperature and time was used. Extracted BGS were subjected to heat-moisture treatment (HMT) at 80-120 °C for 30-90 min at different moisture levels of 15% (HMT 15-BGS), 25% (HMT 25-BGS) and 35% (HMT 35-BGS). The optimum HMT conditions for BGS were found to be 80 °C for 30 min (HMT 15), 105.74 °C for 30 min (HMT 25), and 113.16 °C for 30 min (HMT 35). The desirability values of the obtained optimum conditions were 0.63 (HMT 15) and 1.00 (HMT 25 and 35). In HMT 35-BGS, water absorption capacity was significantly affected by the quadratic effect of temperature and time. In contrast, solubility was significantly affected by the linear effect of time and the quadratic effect of temperature. Temperature and treatment time had no significant effect (p ≥ 0.05) on the differential scanning calorimetry thermal properties of HMT 15, 25 and 35-BGS. Scanning electron micrographs of optimised BGS showed round and oval-shaped starch granules ranging from 4.2 to 4.7 mm (width) and 10 μm for length. Unmodified and optimised HMT-BGS showed characteristic FTIR bands linked with common starches. All BGS samples displayed multiple vibrations in the region below 1000 cm^-1 due to the skeletal vibrations of the glucose pyranose ring.

Structure, in vitro starch digestibility and physicochemical properties of starch isolated from germinated Bambara groundnut

This study investigated the effect of germination time (0, 24, 48 and 72 h) on the physicochemical characteristics, in vitro starch digestibility and microstructural changes in Bambara groundnut starch. The starch yield, lightness (L*) value, amylose content and resistant starch contents of isolated starches decreased significantly (p ≤ 0.05) with increasing germination time. Scanning electron microscopy revealed that starch from raw and germinated Bambara grains were smooth with no evidence of starch degradation and were mainly oval shaped, with some granule's irregular and kidney shaped. Water absorption capacity (1.33-1.90 g/g), swelling power (2.12-16.53 g/g), solubility index (1.14-13.04 g/g), and dispersibility (75.92-86.47%) greatly increased as germination timed increased. Germination did not alter the X-ray diffraction pattern (Type-A) but increased the relative crystallinity of the starches. The peak gelatinization temperatures (73.23-73.91 °C) of starch from germinated Bambara were significantly higher than native starch (72.81 °C). Native starch and starch from germinated Bambara grains had substantially high proportion of resistant starch (approx. 73%) and high pasting temperatures (approx. 88 °C). Conclusively, germination significantly changed starch structure at molecular level and impacted functionality.

Plant growth-promoting rhizobacteria for orphan legume production: Focus on yield and disease resistance in Bambara groundnut

Orphan legumes are now experiencing growing demand due to the constraints on available major food crops. However, due to focus on major food crops, little research has been conducted on orphan legumes compared to major food crops, especially in microbiome application to improve growth and yield. Recent developments have demonstrated the enormous potential of beneficial microbes in growth promotion and resistance to stress and diseases. Hence, the focus of this perspective is to examine the potential of plant growth promoting rhizobacteria (PGPR) to improve Bambara groundnut yield and quality. Further insights into the potential use of PGPR as a biological control agent in the crop are discussed. Finally, three PGPR genera commonly associated with plant growth and disease resistance (Bacillus, Pseudomonas, and Streptomyces) were highlighted as case studies for the growth promotion and disease control in BGN production.

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°C for 48 hr (BAS), and heat-moisture treated at 100°C for 16 hr 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 30 μm, 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.