Impact of germination on the proximate composition, functional properties, and structural characteristics of black soybean (Glycine max L. Merr)

This study aimed to investigate the impact of germination on the quality of black soybean flour (BSF). The black soybeans were germinated for different time period (24, 48, and 72 h), and the impact on proximate composition, functional, structural, and antioxidant properties of the obtained flour was evaluated. Germination process resulted in significant (p <= 0.05) increase in protein (39.46 +/- 0.08-43.30 +/- 0.05 g/100 g), crude fiber (7.55 +/- 0.15-10.31 +/- 0.16 g/100 g), and ash (5.95 +/- 0.04-6.28 +/- 0.01 g/100 g) content as compared with raw black soybean flour (RBSF). Further, significant variation in color attributes, functional properties, and pasting characteristics of raw and germinated black soybean flour (GBSF) was observed. Significant increase in total phenolic content (6.76 +/- 0.05 to 9.30 +/- 0.04 mg GAE/g), total flavonoid content (2.45 +/- 0.04 to 4.32 +/- 0.02 mg QE/g), and DPPH radical scavenging activity (41.31%-60.20%) was observed post germination (24-72 h). Scanning electron micrographs (SEMs) showed that germination resulted in microstructural changes in starch and protein matrix owing to activation of hydrolytic enzymes. Further, X-ray diffraction patterns elucidate significant reduction in crystallinity of GBSF (42.54%-44.48% for 24-72 h) in comparison to RBSF (45.75%).