Pea cell wall integrity controls the starch and protein digestion properties in the INFOGEST in vitro simulation

Dose-dependent impact of intact cell fraction on in vitro starch digestion of common bean-based flour blends

Pulse flours consisting of isolated cotyledon cells (ICC) have been incorporated in foods with delayed amylolysis. To optimize the cost-benefit ratio, understanding how the dosage of cellular ingredient affects starch digestibility is essential. Therefore, dose-response relationships were established to evaluate the sensitivity of amylolysis kinetics to the inclusion of intact cells in whole common bean-based flours. Conventional raw-milled and innovative cellular flours of Epic red common beans were blended in different proportions, creating a range of blends with varying microstructures. Obtained dose-response relationships were validated for Montcalm red and black bean. For all varieties, an increasing dosage of cellular ingredient decreased amylolysis rates, while not affecting final extents. Bean variety-dependent linear dose-response relationships were established between the fraction of raw-milled flour and amylolysis. Dosages of intact cells decreased the amylolysis rate in a bean-specific manner, creating potential for impacted postprandial responses.

Influence of salts adopted in soaking treatments on the pulse cell wall matrix and in vitro digestion kinetics of starch

Starch is the major component of pulse cotyledons and a primary energy source in the human diet. Its digestion is influenced by intrinsic structure and processing-induced changes at cellular level. This study investigated the effects of monovalent, divalent, and trivalent salts on cell-wall structure and in vitro digestion properties of intracellular starch. Whole peas were soaked in salt-solutions with pH ranging from highly-acidic (1.5-4.5) to alkaline (10-11) and cooked cotyledon cells were isolated. Alkaline salt treatment enhanced water absorption, cell separation, yield, starch digestion, and fluorescence, while reduced particle size, galacturonic acid, protein content, and gelatinization temperatures compared to slightly-acidic salt treatments. In contrast, highly-acidic salt treatments caused slight cell rupture, reduced water absorption, yield, and nutritional content but increased starch crystallinity, gelatinization temperatures, and digestion with increased fluorescence. These findings show that salt-induced pH modulation can regulate starch digestion, providing insights into dietary management and metabolic health.

Understanding the structural differences in chickpea globulins and their relationship with in vitro protein digestibility

The relationship between structural protein differences and changes in legumin, vicilin, and chickpea globulin during digestion and protein digestibility has not yet been fully explored. In this study, we characterized the conformational properties and the secondary structures of chickpea protein isolates (globulin), legumin, and vicilin before and after in vitro digestion to understand their roles in protein digestibility. The globulins were characterized by size, surface charge, hydrophobicity, sulfhydryl group content, and solubility. Protein hydrolysis was determined by the OPA method and electrophoresis. The structural changes were elucidated using FTIR spectroscopy. Vicilin had a bimodal particle size distribution and high polydispersity, indicating more heterogeneous particles with lower surface hydrophobicity, fewer free SH groups, and higher solubility (62%) than those of legumin and globulin. Turbidity was correlated with the aggregation index, with legumin exhibiting the highest value. During the gastric phase, in contrast to legumin (34.2%) and vicilin (31.4%), the protein hydrolysis was the highest in globulin fraction (42.2%). However, at the intestinal level, vicilin exhibited highly digested proteins (99%), as confirmed by SDS-PAGE. FTIR analysis demonstrated differences in secondary structure changes between vicilin with an increase in random coils (22%) and globulin and legumin, which displayed highly parallel β-sheet structures (28.7% and 26%, respectively). These results highlight the importance of conformational switching in the secondary structure of globulins for protein digestibility. Promoting unorganized secondary structures, high solubility, and low aggregation improves globulin protein digestibility. Examination of the structure and digestion of chickpea globulins provides valuable information for the development of plant-based products.

The influence of pulse cell wall structure and cellular protein matrix on the in vitro digestion kinetics of starch: A dual encapsulation mechanism

The intrinsic characteristics and extrinsic processing of whole-pulse food modulate the starch digestion rate and extent. This study investigated the dual encapsulation mechanism of cell wall structure and protein matrix on the in vitro digestion properties of intracellular starch, using an isolated whole-pulse food model of intact pea cotyledon cells subjected to alkaline buffer and enzymatic treatments. Results showed that intact cells with the maximum protein matrix content (18.9 %) exhibited the lowest peak temperature (71.4 °C, uncooked and 58.1 °C, cooked), enthalpy change (3.4 J/g, uncooked and 2.0 J/g, cooked), relative crystallinity (11.6 %), and starch digestion rate (0.0248 min-1) and extent (11.9 %) compared to alkaline buffer and enzymatic treatments. Even after enzymatic treatment, cells with minimal protein matrix content (1.8 %) exhibited a starch digestion rate (0.0387 min-1) and extent (39.7 %), which were still lower than those of isolated starch (0.0480 min-1 and 56.8 %). These findings indicate that the protein matrix and cell walls act as a dual encapsulation system to slow starch hydrolysis. This provides a theoretical basis and technical guidance for developing low-glycemic whole-pulse foods.

Unraveling cereal physical barriers composed of cell walls and protein matrix: Insights from structural changes and starch digestion

Physical barriers composed of cell walls and protein matrix in cereals, as well as their cooking changes, play important roles in starch digestion. In this study, the physical barriers of native and cooked highland barley (HB), brown rice (BR), and oats (OA) kernels and their contribution to starch digestion were investigated. The resistant starch content was similar in cereal flours, but varied among cooked kernels (HB > BR > OA: 45.05 %, 10.30 %, and 24.71 %). The water adsorption, gelatinization enthalpy, and decrease in hardness of HB kernels were lower than those of OA and BR kernels. Microstructural observations of native kernels showed that HB had the thickest cell walls. After cooking, the lowest cell wall deformation and a dense continuous network developed from the protein matrix were observed in HB kernels. During digestion, undigested starch granules encapsulated by the stable cell walls and strong protein network were observed in HB kernels, but not in BR or OA kernels. Furthermore, the heavily milled HB kernels still had more resistant starch than the intact OA and BR kernels. Therefore, the physical barriers of HB kernels exhibited stronger inhibition of starch gelatinization and digestion. Differences in cereal physical barriers led to various inhibitory effects.

Targeted hydrothermally induced cell biopolymer changes explain the in vitro digestion of starch and proteins in common bean (Phaseolus vulgaris) cotyledons

Digestion of macro-nutrients (protein and starch) in pulses is a consequence of the interplay of both extrinsic (process-related) and intrinsic (matrix-dependent) factors which influence their level of encapsulation and physical state, and therefore, their accessibility by the digestive enzymes. The current work aimed at understanding the consequences of hydrothermally induced changes in the physical state of cell biopolymers (cell wall, protein, and starch) in modulating the digestion kinetics of starch and proteins in common beans. The hydrothermal treatments were designed such that targeted microstructural/biopolymer changes occurred. Therefore, bean samples were processed at temperatures between 60 and 95 °C for 90 minutes. It was demonstrated that these treatments allowed the modulation of starch gelatinization, protein denaturation and cell separation. The specific role of hydrothermally induced starch gelatinization and protein denaturation, alongside enhanced cell wall permeability on the digestion kinetics of common bean starch and proteins is illustrated. For instance, bean samples processed at T > 70 °C were marked by higher levels of starch digestibility (Cf values above 47%) compared to the partially (un-)gelatinized samples (processed at T ≤ 70 °C) (Cf values below 35%). Similarly, samples processed at T > 85 °C exhibited significantly higher levels of protein digestibility (Cf values above 47%) resulting from complete protein denaturation. Moreover, increased permeability of the cell wall to digestive enzymes in these samples (T > 85 °C) increased levels of digestibility of both gelatinized starch and denatured proteins. This study provides an understanding of the potential use of hydrothermal processing to obtain pulse-based ingredients with pre-determined microstructural and nutritional characteristics.

Co-ingestion of Cereals and Legumes during Infant Complementary Feeding: Starch and Protein in vitro Digestion

This study explores the impact of co-ingesting cereals and legumes on starch and protein during simulated infant in vitro digestion. Various legumes (chickpeas, lentils, peas) were added to cereals (durum wheat, brown rice, white maize), and their effects on starch and protein hydrolysis were analyzed. Substituting 50% of cereal with legumes increased proteins, minerals, and dietary fiber. Infant food with legumes exhibited smoother pasting properties. Legumes in cereal purées led to varying starch hydrolysis trends, with the lowest values in durum wheat with chickpea and all cereal blends with peas. Resistant starch levels exceeding 50% were found in infant food samples. Digested protein hydrolysis increased with legumes in durum wheat, except for peas. Brown rice mixtures decreased significantly compared to the control with chickpeas (61%) and peas (42%), while lentil blends increased by 46%. Legumes generally did not significantly affect starch bioavailability, even with α-amylase inhibitors. Lentil-cereal purées could enhance infant food nutritional value.

Formation, Structural Characterization, and Functional Properties of Corn Starch/Zeaxanthin Composites

Zeaxanthin is a natural xanthophyll carotenoid and the main macular pigment that protects the macula from light-initiated oxidative damage, but it has poor stability and low bioavailability. Absorption of this active ingredient into starch granules as a carrier can be used to improve both zeaxanthin stability and controlled release. Optimization using three variables judged important for optimizing the system (reaction temperature of 65 °C, starch concentration of 6%, and reaction time of 2 h) was conducted for incorporation of zeaxanthin into corn starch granules, aiming for high zeaxanthin content (2.47 mg/g) and high encapsulation efficiency (74%). Polarized-light microscopy, X-ray diffraction, differential scanning calorimetry, and Fourier transform infrared spectroscopy showed that the process partially gelatinized corn starch; additionally, it showed the presence of corn starch/zeaxanthin composites, with the zeaxanthin successfully trapped in corn starch granules. The half-life time of zeaxanthin in corn starch/zeaxanthin composites increased to 43 days as compared with that of zeaxanthin alone (13 days). The composites show a rapid increase in zeaxanthin release with in vitro intestinal digestion, which is favorable for possible use in living systems. These findings could have application in designing effective starch-based carriers of this bioactive ingredient with enhanced storage stability and improved intestines-targeted controlled-release delivery.

Size exclusion chromatography to evaluate in vitro proteolysis: a case study on the impact of microstructure in pulse powders

Cellular pulse ingredients are increasingly being studied but little knowledge on their proteolysis patterns upon digestion is available. This study investigated a size exclusion chromatography (SEC) approach to study in vitro protein digestion in chickpea and lentil powders, providing novel insights into proteolysis kinetics and the evolution of molecular weight distributions in the (solubilized) supernatant and (non-solubilized) pellet fractions. For the quantification of proteolysis, SEC-based analysis was compared to the commonly used OPA (o-phthaldialdehyde) approach and nitrogen solubilized upon digestion, leading to highly correlated proteolysis kinetics. Generally, all approaches confirmed that microstructure dictated proteolysis kinetics. However, SEC analysis delivered an additional level of molecular insight. For the first time, SEC revealed that while bioaccessible fractions reached a plateau in the small intestinal phase (around 45-60 min), proteolysis continued in the pellet, forming smaller but mostly insoluble peptides. SEC elutograms showed pulse-specific proteolysis patterns, unidentified using other current state-of-the-art methods.

The microbiota and metabolites during the fermentation of intact plant cells depend on the content of starch, proteins and lipids in the cells

Intact cells, as the smallest unit of whole foods, were isolated from three legume crops and fermented with human faecal inoculum to elucidate the effect of food macro-nutrients compositional difference (starch, proteins and lipids) on in vitro colonic fermentation profiles. After 48 h of fermentation, the highest production of short-chain fatty acids (SCFAs) were observed for the pea cells, abundance in starch (64.9 %, db). In contrast, branch chain fatty acids (BCFAs) were the major metabolites for protein-enriched soybean cells (protein content 56.9 %, db). The peanut cells rich in lipids (49.2 %, db) has the lowest fermentation rate among the three varieties. Correspondingly, pea cells favoured the growth of Bifidobacterium, whereas soybean and peanut cells promoted an abundance of Bacteroides and Shigella, respectively. Furthermore, except the intact pea cells promoting the abundance of butyrate producer Roseburia, a similar fermentation pattern was found between intact and broken cells suggesting that macro-nutrient types, rather than structure, dominate the production of metabolites in colonic fermentation. The findings elucidate how the food compositional difference can modulate the gut microbiome and thus provide the knowledge to design whole food legumes-based functional foods.

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.

Release of Bioactive Peptides from Erythrina edulis (Chachafruto) Proteins under Simulated Gastrointestinal Digestion

The estimated and concerning rise in world population over the next few years and the consequent increase in food demand will lead to a deterioration in global food security. To avoid or reduce this world crisis, informed and empowered consumers are turning to sustainable and nutrient-rich foods that substitute animal products, also reducing their associated environmental impact. Moreover, due to the demonstrated influence of diet on the risk of high incidence and mortality of noncommunicable diseases, the current established food pattern is focused on the consumption of foods that have functionality for health. Among these new foods, traditional and underutilized plants are gaining interest as alternative protein sources providing nutritional and biological properties. In this work, the potential of Erythrina edulis (chachafruto) proteins as a source of multifunctional peptides after transit through the gastrointestinal tract has been demonstrated, with antioxidant and immunostimulating effects in both biochemical assays and cell culture. While low molecular weight peptides released during the digestive process were found to be responsible for protection against oxidative stress mediated by their radical scavenging activity, high molecular weight peptides exerted immunostimulating effects by upregulation of immunoresponse-associated biomarkers. The findings of this study support the promising role of chachafruto proteins as a new antioxidant and immunostimulatory ingredient for functional foods and nutraceuticals.