Compositional characterization of starch, proteins and lipids of long bean, dwarf long bean, mung bean and French bean seed flours

Abstract

Four underutilized legumes comprised of mung bean, long bean, dwarf long bean and French bean were investigated for their total starch, dietary fibre, amylose, amylopectin and resistant contents along with proteins and lipids profiles employing standard methods in order to explore appropriate end uses. Results showed significant variations (p<0.05) in the fat, protein, moisture, ash, total dietary fibre, carbohydrate, starch, amylose and amylopectin contents of all the four legume seeds Flours. Mung bean, long bean, dwarf long bean, and French bean showed carbohydrates contents of 55.24, 49.63, 48.12 and 45.56 g/100 g, respectively. Dwarf long bean, long bean and mung bean recorded total starch of 38.39, 49.78 and 57.68 g/100 g, respectively. Whereas French bean had the highest total dietary fibre of 16.91 g/100 g and dwarf long bean the highest amylopectin (86.67 g/100 g), both dwarf long bean and long bean recorded insoluble dietary fibre and soluble dietary fibre in the range of 7.25 to 14.58 g/100 g and 0.05 to 1.25 g/100 g, respectively, however, all the seed flours showed higher content of insoluble dietary fibre than soluble dietary fibre. Significant differences (p<0.05) observed in the total starch, resistant starch and non-resistant starch content of all the 4 samples. Non-resistant starch was the predominant constituents of the total of all the seed flours with mung bean showing the highest value (54.16 g/100 g) followed by long bean, dwarf long bean and French bean with 48.74, 37.73 and 16.88 g/100 g, respectively. Though the beans had low amylose contents, their amino acids score and patterns surpassed the FAO reference proteins and their saturated and unsaturated fatty acids ratio falls within FAO allowed limits. This study highlights the hidden potentials of these non-conventional legumes as sources of quality proteins, functional foods, healthy fats and dietary fibres.