Amylose content, molecular structure, physicochemical properties and in vitro digestibility of starches from different mung bean (Vigna radiata L.) cultivars

Abstract

Physicochemical and in vitro digestibility characteristics of starches isolated from six cultivars of mung bean (Vigna radiata L.) were studied. Significant differences (p < 0.05) were observed between the cultivars with respect to amylose content (29.9-33.6%), relative crystallinity (29.0 to 31.7%), particle diameter (16.2-17.1 mu m) and molecular weight of amylopectin (260-289 x 10(6) g/mol). The scanning electron micrographs revealed the presence of large oval to small round shape granules with average particle diameter of 16.2-17.1 mu m. The X-ray diffraction pattern was of the C-type. The enthalpies of gelatinization and retrogradation were 8.9-10.3 and 4.6-6.3 J/g, respectively. The amounts of slowly digesting and resistant starch of mung bean followed the order: PBM-1 > SML-32 > ML-613 > SML-134 > ML-267 > ML-5 and ML-5 > ML-267 > SML-134 > ML-613 > SML-32 > PBM-1, respectively. The six starches exhibited significant (p < 0.05) differences in their pasting parameters. Correlation analysis showed that amylose content, granule diameter and relative crystallinity values were important in determining thermal, pasting and in vitro digestibility of starches.