In vitro starch and protein digestion kinetics of cooked Bambara groundnuts depend on processing intensity and hardness sorting

When pulse seeds from a single batch are cooked, considerable variability of hardness values in the population is usually observed. Sorting the seeds into hardness categories could reduce the observed diversity and increase uniformity. Therefore, we investigated the effect of processing intensity whether or not combined with sorting into hardness categories on the in vitro starch and protein digestion kinetics of cooked Bambara groundnuts (cooking times 40 min and 120 min). The average hardness values were 89 ± 32 N and 42 ± 20 N for 40 min and 120 min cooking time, respectively. The high standard deviation of hardness for each cooking time revealed a high level of diversity amongst the seeds. Individual cells were isolated from (non-)sorted seeds before simulating digestion. The estimated lag phase describing the initial phase of starch digestion was not significantly different despite the processing intensity or the hardness category, implying that cell wall barrier properties for these samples were not majorly different. However, the rate constants and the extents of starch digestion of samples cooked for 40 min were significantly higher for the low hardness (50-65 N) compared to the high hardness (80-95 N) category (0.71 vs 1.02 starch%/min and 63 vs 77%, respectively). Kinetic evaluation of digested soluble protein (after acid hydrolysis of the digestive supernatant) showed that low hardness samples were digested faster than high hardness samples (0.037 vs 0.050 min-1). The faster protein hydrolysis in the low hardness samples was accompanied by faster starch digestion, indicating the possible role of the protein matrix barrier. Individual cells of comparable hardness obtained from the two different processing times had similar starch and protein digestion kinetics. Our work demonstrated that, beyond cooking time, hardness is a suitable food design attribute that can be used to modulate starch and protein digestion kinetics of pulse cotyledon cells.status: Published onlin

How Cooking Time Affects In Vitro Starch and Protein Digestibility of Whole Cooked Lentil Seeds versus Isolated Cotyledon Cells

Lentils are sustainable sources of bioencapsulated macronutrients, meaning physical barriers hinder the permeation of digestive enzymes into cotyledon cells, slowing down macronutrient digestion. While lentils are typically consumed as cooked seeds, insights into the effect of cooking time on microstructural and related digestive properties are lacking. Therefore, the effect of cooking time (15, 30, or 60 min) on in vitro amylolysis and proteolysis kinetics of lentil seeds (CL) and an important microstructural fraction, i.e., cotyledon cells isolated thereof (ICC), were studied. For ICC, cooking time had no significant effect on amylolysis kinetics, while small but significant differences in proteolysis were observed (p < 0.05). In contrast, cooking time importantly affected the microstructure obtained upon the mechanical disintegration of whole lentils, resulting in significantly different digestion kinetics. Upon long cooking times (60 min), digestion kinetics approached those of ICC since mechanical disintegration yielded a high fraction of individual cotyledon cells (67 g/100 g dry matter). However, cooked lentils with a short cooking time (15 min) showed significantly slower amylolysis with a lower final extent (~30%), due to the presence of more cell clusters upon disintegration. In conclusion, cooking time can be used to obtain distinct microstructures and digestive functionalities with perspectives for household and industrial preparation

Utilizing Hydrothermal Processing to Align Structure and In Vitro Digestion Kinetics between Three Different Pulse Types

Processing results in the transformation of pulses’ structural architecture. Consequently, digestion is anticipated to emerge from the combined effect of intrinsic (matrix-dependent) and extrinsic (processed-induced) factors. In this work, we aimed to investigate the interrelated effect of intrinsic and extrinsic factors on pulses’ structural architecture and resulting digestive consequences. Three commercially relevant pulses (chickpea, pea, black bean) were selected based on reported differences in macronutrient and cell wall composition. Starch and protein digestion kinetics of hydrothermally processed whole pulses were assessed along with microstructural and physicochemical characteristics and compared to the digestion behavior of individual cotyledon cells isolated thereof. Despite different rates of hardness decay upon hydrothermal processing, the pulses reached similar residual hardness values (40 N). Aligning the pulses at the level of this macrostructural property translated into similar microstructural characteristics after mechanical disintegration (isolated cotyledon cells) with comparable yields of cotyledon cells for all pulses (41–62%). We observed that processing to equivalent microstructural properties resulted in similar starch and protein digestion kinetics, regardless of the pulse type and (prolonged) processing times. This demonstrated the capacity of (residual) hardness as a food structuring parameter in pulses. Furthermore, we illustrated that the digestive behavior of isolated cotyledon cells was representative of the digestion behavior of corresponding whole pulses, opening up perspectives for the incorporation of complete hydrothermally processed pulses as food ingredients