Structural and compositional variations in the intact pulse cotyledon cells determine the in vitro digestion kinetics...

Cooked cotyledon cells were isolated from pulses to investigate how compositional, morphological, and structural variations in encapsulated starch influence in vitro digestion rate and extent of starch. Significant inter-varietal differences were observed in starch (52.2-71.6 %), protein (11.4-22.1 %), dietary fiber (11.5-25.1 %), cell size (85-176 μm), and cell wall thickness (1.6-3.7 μm). Although cooking largely reduced starch crystallinity, runner beans and red kidney beans retained residual birefringence and higher crystallinity (3.5-8.5 %). Starch hydrolysis varied widely among varieties (C₁₂₀ = 23.1-71.4 %), with limited digestion observed in thick-walled, protein- and fiber-rich cells, while thinner-walled cells exhibited more uniform hydrolysis. Pearson's correlation analysis identified enthalpy change, crystallinity, and galacturonic acid content as the strongest negative correlates of starch hydrolysis, followed by amylose content and cell wall thickness. These results demonstrate that starch digestibility in pulses is constrained by multiple overlapping compositional and structural barriers, providing mechanistic insight into their typically low glycemic responses.