Starch digestion in intact pulse cells depends on the processing induced permeability of cell walls

Enzyme digestion of starch granules encapsulated within cell walls in pulse depends on both the intactness of cellular structure as well as the retention of the ordered structure of starch during processing. However, the role of cell wall permeability in starch digestion, as affected by processing conditions, has not been fully elucidated. In this study, Kubali bean cells were isolated under different processing conditions (i.e., high pressure-heating, hydrothermal processing, and acid-alkali treatments) individually and in combinations to elucidate the structure and in vitro digestion of entrapped starches in the cells. The morphological features and crystalline structure of entrapped starches suggest that intact cell walls hinder the starch gelatinization, which in turn lowers the enzyme susceptivity. Alteration of cell wall permeability induced by different processing conditions is further evaluated through the diffusion of fluorescence-tagged dextran probes. Among all the treatments, cells isolated with the pressure-cooking method exhibited higher cell wall permeability. The study suggests that the in vitro starch digestion of plant foods can be optimized through the selection of processing method that has the least impact on cell wall permeability.