Abstract
Green-kernel black bean (Vigna cylindrica (L.) Skeels) were processed with various treatments including soaking, roasting, cooking, autoclave and germination. The effects of these treatments on the chemical compostion, mineral, anti-nutrients, antioxidant and physical properties of the resultant flours were analyzed. The results indicate that green-kernel black bean was excellent sources of dietary fiber (165.4 g/kg), magnesium (2190 mg/kg), anthocyanin (791.6 mg/kg) and phenolic compounds (4.4 g gallic acid equivalent/kg), which were virtually higher than those reported for other pulses. Among the studied processing methods, cooking and autoclave provided the most evident effects on all flour characteristics, where the water holing capacity was enhanced and the flour became brighter. In addition, the levels of anti-nutrients such as tannin, saponin and trypsin inhibitors remarkably reduced and hence the starch digestibility was improved. However, antioxidant compounds were degraded or lost, leading to lower antioxidant capacities in terms of 2,2-diphenyl-2-picrylhydrazyl hydrate (DPPH) free radical scavenging ability and ferric reducing antioxidant power (FRAP). On the other hand, germination resulted in lesser reduction of anti-nutrients but lesser losses of antioxidants and good starch digestibility. Meanwhile, roasting caused the least effects on flour characteristics but was still able to partially degrade anti-nutrients.
Keywords:
Vigna cylindrica; anti-nutrient; dietary fiber; magnesium; anthocyanin; glycemic index