Heterogeneity in composition and morphology drives digestion in cotyledon cells from seven pulse batches

Pulses are key components of sustainable, healthy diets. Their macronutrients are bioencapsulated within cotyledon cells, modulating the interlinked digestion of starch and protein. Yet, the exact cell properties governing digestion kinetics remain unclear. We investigated how compositional and morphological properties of cotyledon cells from seven pulse batches (both the same and different pulse types) relate to their digestion behavior. For this, individual cotyledon cells (ICC) were isolated from seeds cooked to batch-specific equivalent cooking times, characterized for composition and morphology, and in vitro starch and protein digestion was assessed (INFOGEST 2.0). While chickpea ICCs consistently showed the slowest amylolysis, no correlations with ICC properties could be identified as a potential cause. Proteolysis kinetics correlated negatively with equivalent cooking time and cell wall-related barrier descriptors. Composition and morphology varied substantially between and within pulse types. We hypothesized that high heterogeneity within pulse ICCs potentially prevented the identification of clear links between cell properties and digestion. To overcome this hurdle, the impact of black bean cotyledon cell size on digestion was investigated upon sorting the ICCs into more homogenous size fractions. As such, a clear impact of cell size was observed, with more rapid starch and protein digestion in smaller cells. This effect was not apparent in unsorted samples, highlighting the importance of considering batch heterogeneity when studying pulse digestion.