Himalayan kidney bean germplasm: Grain-flour characteristics, structural-functional properties and in-vitro digestibility of starches

• Grains, flours and starches of kidney beans showed significant differences.
• Dark coloured lines had higher antioxidant activity.
• Accessions showed differential accumulation of trypsin inhibitory polypeptides.
• Starches showed differences in crystallinity, particle size and amylose content.
• Starches with higher amylose content had more resistant starch.

Diversity and relationship among grain, flour and starch characteristics of seventeen different kidney bean accessions were evaluated. Size of starch granules and thickness of protein matrix in cotyledon varied with grain size which also affected their hydration and textural properties. Antioxidant activity (AOA) ranged from 5.5% to 44.9% and was negatively correlated with L⁎ and b⁎ values. Accessions with higher degree of lightness and yellowness had significantly lower AOA as compared to other lines. Differential accumulation of trypsin inhibitory polypeptides was observed among the accessions. SEM revealed that starch granules were intact, smooth and round to elliptical. Crystallinity (1047/1022 cm− 1) of starches varied from 0.23 to 0.98 which could be attributed to difference in their amylose content (17.4%-40.7%). The size of the starch granules ranged between 1.64 and 176 μm. Rapidly digestible, slowly digestible and resistant starch (RS) content of starches ranged from 11.1% to 19.5%, 8.5% to 17.3% and 63.9% to 76.1%, respectively. RS showed significant positive correlations with amylose content of starches.