Diversity in characteristics of starch amongst rice bean (Vigna umbellate) germplasm: Amylopectin structure, granules size distribution, thermal and rheology

Diversity in amylopectin structure, granule size distribution, thermal and rheological properties of starches amongst rice bean germplasm was evaluated. Starches from different rice bean lines showed unimodal and bimodal distribution profiles for the granules size, which ranged between 0.5 and 105 μm. Amylopectin units chains with different degree of polymerization (DP) vary significantly (short- (DP 6–10), medium- (DP 11–20) and long-chains (DP 21–30) ranged between 19.85 and 28.42%, 60.69 and 65.05%, and 8.67–15.67%, respectively). Principal component analysis indicated negative relationship of thermal parameters with amylose content. Peak viscosity, trough viscosity and breakdown viscosity were positively related to large size granules (30 to 60 and 60–105 μm) and negatively to amylose content.

► Rice bean germplasm showed wide diversity in amylopectin structure, granule size distribution, thermal and rheological properties.
► Rice bean starches showed unimodal and bimodal distribution profiles for the granules size.
► Amylopectin short- (DP 6–10), medium- (DP 11–20) and long-chains (DP 21–30) vary the proportion of granules of different sizes.