Identification of chickpea seed proteins resistant to simulated in vitro human digestion

Evaluation of Total Isoflavones in Chickpea (Cicer arietinum L.) Sprouts Germinated under Precursors (p-Coumaric Acid and L-Phenylalanine) Supplementation

Cicer arietinum L. (Bengal gram, chickpea) is one of the major pulse crops and an important part of traditional diets in Asia, Africa, and South America. The present study was conducted to determine the changes in total isoflavones during sprouting (0, 3, and 7 days) along with the effect of two precursor supplementations, p-coumaric acid (p-CA) and L-phenylalanine (Phe), in C. arietinum. It was observed that increasing sprouting time up to the seventh day resulted in ≈1282 mg 100 g-1 isoflavones, which is approximately eight times higher than chickpea seeds. The supplementation of Phe did not affect the total length of sprouts, whereas the supplementation of p-CA resulted in stunted sprouts. On the third day of supplementation with p-CA (250 mg L-1), the increase in the total phenolic content (TPC) (80%), daidzein (152%), and genistin (158%) contents were observed, and further extending the supplementation reduced the growth of sprouts. On the seventh day of supplementation with Phe (500 mg L-1), the increase in TPC by 43% and genistin content by 74% was observed compared with non-treated sprouts; however, the total isoflavones content was found to be 1212 mg 100 g-1. The increased TPC was positively correlated with the 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activity (r = 0.787) and ferric-reducing antioxidant potential (FRAP) (r = 0.676) activity. This study suggests that chickpea sprouts enriched in TPC and antioxidants can be produced by the appropriate quantity of precursor supplementation on a particular day. The results indicated major changes in the phytochemical content, especially daidzein and genistin. It was also concluded that the consumption of 100 g of seventh-day sprouts provided eight times higher amounts of isoflavones in comparison to chickpea seeds.

Combination of three null mutations affecting seed protein accumulation in pea (Pisum sativum L.) impacts positively on digestibility

The presence of so-called anti-nutritional factors can reduce the bioavailability of nutrients following consumption of seeds which are otherwise an excellent source of proteins, carbohydrates and micronutrients. Among the proteins associated with negative effects on quality in pea (Pisum sativum L.) seeds are lectin, pea albumin 2 (PA2) and trypsin inhibitors (TI). Here we have investigated the impact of these proteins on protein digestibility and amino acid availability, using naturally occurring and derived mutant lines of pea lacking these proteins. The mutations were stacked to generate a triple mutant which was compared with a wild-type progenitor and a line lacking the major seed trypsin inhibitors alone. In vitro digestions following the INFOGEST protocol revealed significant differences in the degree of hydrolysis, protein profile and apparent amino acid availability among the pea variants. Proteins resistant to digestion were identified by MALDI-TOF mass spectrometry and amino acid profiles of digested samples determined. The results indicate that pea seeds lacking certain proteins can be used in the development of novel foods which have improved protein digestibility, and without negative impact on seed protein concentration or yield.

Alternations in the multilevel structures of chickpea protein during fermentation and their relationship with digestibility

This study investigated the effects of fermentation on in vitro protein digestibility of chickpeas and their relationship with the variations of multilevel structures of chickpea protein. The results showed that lactobacillus fermentation not only increased the solubility of chickpea protein but also enhanced the hydrolysis of protein during gastric and intestinal digestion by altering the multilevel structures of chickpea protein. The degree of hydrolysis, free amino acid content, and sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) revealed that macromolecule chickpea protein was hydrolyzed during fermentation. Raman and UV spectroscopy scans indicated that the α-helix content increased while the content of β-sheet in chickpea protein dropped significantly after fermentation. As for fermented chickpea protein, the aromatic acid residues were gradually more exposed than the unfermented chickpea protein, and the intramolecular disulfide bond was generally converted to the intermolecular form. Our findings showed that fermentation changed the multilevel structures of chickpea protein, degrading spherical structures into looser states that were more responsible for their effective hydrolysis during digestion. Furthermore, better digestibility of chickpea protein would stimulate the use of chickpea fermentation in food products.

Legume Seed Protein Digestibility as Influenced by Traditional and Emerging Physical Processing Technologies

The increased consumption of legume seeds as a strategy for enhancing food security, reducing malnutrition, and improving health outcomes on a global scale remains an ongoing subject of profound research interest. Legume seed proteins are rich in their dietary protein contents. However, coexisting with these proteins in the seed matrix are other components that inhibit protein digestibility. Thus, improving access to legume proteins often depends on the neutralisation of these inhibitors, which are collectively described as antinutrients or antinutritional factors. The determination of protein quality, which typically involves evaluating protein digestibility and essential amino acid content, is assessed using various methods, such as in vitro simulated gastrointestinal digestibility, protein digestibility-corrected amino acid score (IV-PDCAAS), and digestible indispensable amino acid score (DIAAS). Since most edible legumes are mainly available in their processed forms, an interrogation of these processing methods, which could be traditional (e.g., cooking, milling, extrusion, germination, and fermentation) or based on emerging technologies (e.g., high-pressure processing (HPP), ultrasound, irradiation, pulsed electric field (PEF), and microwave), is not only critical but also necessary given the capacity of processing methods to influence protein digestibility. Therefore, this timely and important review discusses how each of these processing methods affects legume seed digestibility, examines the potential for improvements, highlights the challenges posed by antinutritional factors, and suggests areas of focus for future research.

Lentil Protein and Tannic Acid Interaction Limits in Vitro Peptic Hydrolysis and Alters Peptidomic Profiles of the Proteins

In this study, the nature of lentil protein-tannic acid (LPTA) interaction and its effect on in vitro pepsin digestion were investigated. LPTA mixtures containing 1% w/v LP and 0.001-0.5% TA were prepared and characterized in terms of particle size, thermal properties, and secondary and tertiary structures. A 20-fold increase in particle size was observed in LPTA0.5% compared to LP control (without TA), indicating aggregation. Static quenching of tryptophan residues within the protein hydrophobic folds was observed. Increasing TA levels also enhanced protein thermal stability. Over 50% reduction in free amino groups of LPTA 0.5%, relative to LP, was observed after pepsin digestion. Cleavage specificity of pepsin and peptidomic profile of LP were modified by the presence of TA in LPTA 0.5%. This study showed that 0.5% w/v TA induced protein aggregation and reduced LP digestibility by hindering the accessibility of pepsin to the protein network, thus modifying the profile of released peptides.

Comparison of five chickpea varieties, optimization of hydrolysates production and evaluation of biomarkers for type 2 diabetes

The objective was to compare five varieties of chickpea (Cicer arietinum), sequence the peptides obtained with pepsin-pancreatin digestion, and evaluate their potential as modulators of biochemical markers for type-2 diabetes. In addition, to produce a functional ingredient, by the optimization in the production of hydrolysates using bromelain. Proteins of ground raw, precooked and cooked chickpea, were extracted, isolated, and characterized using SDS-PAGE gel electrophoresis. Hydrolysates were obtained by simulated digestion with pepsin-pancreatin, and resulting peptides were sequenced with LC-MSMS. Response surface methodology was used to optimize the production of hydrolysates with dipeptidyl peptidase IV (DPPIV) inhibition using bromelain. Protein profiles showed fractions of convicilin (>70 kDa), 7S vicilin (43-53 kDa), 11S legumin (35 kDa) and lectins (30-32 kDa) in raw varieties. Albumin fractions 2S (20-26 kDa) were still present in most varieties after 2 h of heat treatment. DPPIV IC₅₀ values from digestive enzymes were better (0.17-2.21 mg/mL) in raw chickpea than in cooked chickpea. α-Glucosidase inhibition at 10 mg protein/mL was highest (32-66%) in precooked chickpea hydrolysates. Hydrolysis with bromelain showed a DPPIV inhibition of 94% for Sierra variety cooked for 15 min with 1:10 E/S ratio and hydrolysis time of 60 min. Peptides with DPPIV inhibition were present from albumin fractions (EVLSEVSF) with 908.44 Da and high hydrophobicity; and from legumin (VVFW, FDLPAL) with 549.29 and 674.36 Da, respectively. In conclusion, high DDPIV inhibition can be obtained from chickpea bromelain hydrolysates, with potential as ingredients in different food applications.

Stress response of lettuce (Lactuca sativa) to environmental contamination with selected pharmaceuticals: A proteomic study

Pharmaceutical compounds have been found in rivers and treated wastewaters. They often contaminate irrigation waters and consequently accumulate in edible vegetables, causing changes in plants metabolism. The main objective of this work is to understand how lettuce plants cope with the contamination from three selected pharmaceuticals using a label free proteomic analysis. A lettuce hydroponic culture, grown for 36 days, was exposed to metformin, acetaminophen and carbamazepine (at 1 mg/L), during 8 days, after which roots and leaves were sampled and analysed using a liquid chromatography-mass spectrometry proteomics-based approach. In roots, a total of 612 proteins showed differentially accumulation while in leaves 237 proteins were identified with significant differences over controls. Carbamazepine was the contaminant that most affected protein abundance in roots, while in leaves the highest number of differentially accumulated proteins was observed for acetaminophen. In roots under carbamazepine, stress related protein species such as catalase, superoxide dismutase and peroxidases presented higher abundance. Ascorbate peroxidase increased in roots under metformin. Cell respiration protein species were affected by the presence of the three pharmaceuticals suggesting possible dysregulation of the Krebs cycle. Acetaminophen caused the main differences in respiration pathways, with more emphasis in leaves. Lettuce plants revealed different tolerance levels when contaminants were compared, being more tolerant to metformin presence and less tolerant to carbamazepine. SIGNIFICANCE: The significant increase of emerging contaminants in ecosystems makes essential to understand how these compounds may affect the metabolism of different organisms. Our study contributes with a detailed approach of the main interactions that may occur in plant metabolism when subjected to the stress induced by three different pharmaceuticals (acetaminophen, carbamazepine and metformin).

Improved estimation of in vitro protein digestibility of different foods using size exclusion chromatography

While the harmonized INFOGEST model provides a physiologically relevant platform for simulated digestion, it needs to be combined with adequate analytical methods to enable quantification and comparison of protein digestibility in different food matrices. We have shown that size exclusion chromatography (SEC) can be used to estimate the proportion of small peptides potentially available for uptake. Combined with determination of total dissolved protein, the % of small peptides per total protein was calculated as a physiologically relevant estimate of protein digestibility (D_SEC). Values for D_SEC differed for casein (87.6%), chicken mince (72.6%), heated pea protein concentrate (67.8%), bread (63%), beef entrecote (57.7%) and pea protein concentrate (57.8%). In contrast to existing methods (TCA soluble protein, free NH₂-groups), the proposed SEC based method gives separate insight into the two fundamental processes during protein digestion (solubilization and break-down), while maintaining the ability to rank digestibility of very different food proteins.

Digestive characteristics and peptide release from wheat embryo proteins in vitro

Due to the scarcity of the data on digestion and metabolism of wheat embryo proteins WEP, a simulated gastrointestinal digestion (SGID) scheme in vitro was utilized to explain the protein hydrolysis and biological activity of WEP during the digestion process. WEP had a certain degree of resistance to gastric digestion, especially the protein with a molecular weight of 50 kDa. In all the samples, no visually intact protein band emerged in sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) during the intestinal phase, which was consistent with a gradually increasing content of released free amino acids. Moreover, the resistant digestion peptides (the amino acid sequences were ISQFXX and GTVX) were identified at the end of the gastrointestinal digestion (GID) product by high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS). Although the complete protein in the sample was degraded, the antioxidant activity was not negatively affected, rather it showed an increasing trend and maintained a higher level of activity. The amount of the β-sheet gradually increased as that of the α-helix declined, the random coil decreased, whereas no obvious change was noticed in β-turn content. The results provide a better understanding for optimal selection of peptide candidates for designing protein products in the food processing industry as well as for WEP digestion and metabolism in the human body.

Evaluation of Changes in Protein Quality of High-Pressure Treated Aqueous Aquafaba

Chickpea cooking water (CCW), known as aquafaba, has potential as a replacement for egg whites due to its emulsion and foaming properties which come from the proteins and starch that leach out from chickpeas into the cooking water. High pressure (HP) processing has the ability to modify the functional characteristics of proteins. It is hypothesized that HP processing could favorably affect the functional properties of CCW proteins by influencing their structure. The objective of this study to evaluate the effect of HP treatment on the associated secondary structure, emulsion properties and thermal characteristics of CCW proteins. A central composite rotatable design is used with pressure level (227-573 MPa) and treatment time (6-24 min) as HP variables, and concentration of freeze dried CCW aquafaba powder (11-29%) as product variable, and compared to untreated CCW powder. HP improves aquafaba emulsion properties compared to control sample. HP reduces protein aggregates by 33.3%, while β-sheets decreases by 4.2-87.6% in which both correlated to increasing protein digestibility. α-helices drops by 50%. It affects the intensity of some HP treated samples, but not the trend of bands in most of them. HP treatment decreases Td and enthalpy because of increasing the degree of denaturation.

Identification and Comparison of Peptides from Chickpea Protein Hydrolysates Using Either Bromelain or Gastrointestinal Enzymes and Their Relationship with Markers of Type 2 Diabetes and Bitterness

The chickpea (Cicer arietinum L.) is one of the most important pulses worldwide. The objective was to identify, compare and evaluate peptides from chickpea hydrolysates produced by two enzymatic treatments. The antidiabetic potential and bitterness of the peptides and induction of bitter receptors were identified in silico. Proteins were isolated from the Kabuli variety. Peptides were produced from the proteins using a simulated digestive system (pepsin/pancreatin, 1:50 Enzyme/Protein, E/P), and these peptides were compared with those produced via bromelain hydrolysis (1:50 E/P). The protein profiles, sequences and characteristics of the peptides were evaluated. The biochemical inhibition and molecular docking of dipeptidyl peptidase-IV (DPP-IV), α-amylase and α-glucosidase were also studied. The molecular docking identified peptides from enzymatic hydrolysis as inhibitors of DPP-IV. The high hydrophobicity of the peptides indicated the potential for bitterness. There was no correlation between peptide length and DPP-IV binding. Peptides sequenced from the pepsin/pancreatin hydrolysates, PHPATSGGGL and YVDGSGTPLT, had greater affinity for the DPP-IV catalytic site than the peptides from the bromelain hydrolysates. These results are in agreement with their biochemical inhibition, when considering the inhibition of sitagliptin (54.3 µg/mL) as a standard. The bitter receptors hTAS2R38, hTAS2R5, hTAS2R7 and hTAS2R14 were stimulated by most sequences, which could be beneficial in the treatment of type 2 diabetes. Chickpea hydrolysates could be utilized as functional ingredients to be included in the diet for the prevention of diabetes.

Pulses' germination and fermentation: Two bioprocessing against hypertension by releasing ACE inhibitory peptides

Angiotensin-Converting Enzyme (ACE) is one of the main blood pressure regulators in the renin-angiotensin system leading to hypertension. Hypertension is known as the modern world disease which increases the risk of serious human health problems. Synthetic drugs and some natural compounds could treat this disease by binding to ACE and reducing its activity. Pulses, one of the legumes group, that are the rich in protein sources in the human diet, have several bioactive compounds with ACE inhibitory (ACE I) properties. However, several processes need to break down proteins and improve ACE I activity in foods. Germination and fermentation, known by bioprocessing, could make releasing bioactive peptides and polyphenols and exhibit ACE I and either other health properties such as antimicrobial, antioxidant, anti-diabetic and anticancer activities. Various factors such as kind of selective culture, temperature, time and humidity affect these processes. This review summarizes relevant studies about the effect of pulses' germination and fermentation to produce ACE I activity compounds and also explains about main parameters affecting the health properties of these two bioprocessing to treat hypertension that could lead to the development of their application in pharmaceuticals instead of synthetic drugs.

Quality of a Chickpea-Based High Protein Snack

A chickpea-based high protein, ready-to-eat snack was prepared using six chickpea types. The chickpea seeds and their corresponding snack products were analyzed for proximate composition, antinutrients, and select quality parameters. Chickpea types had: lipid (4.25% to 6.98%), moisture (6.63% to 9.15%), protein (23.33% to 30.95%), and carbohydrate (54.60% to 60.40%) contents exhibiting significant (P ≤ 0.05) differences. Ash content (1.94% to 2.41%) did not register significant differences. Chickpea types did not show variability in either polypeptide profile or in vitro protein digestibility. In the tested seeds, hemagglutinins and α-amylase inhibitors were not detected, while trypsin (12.73 to 19.58 units/mg sample) and chymotrypsin inhibitors (62.91 to 84.91 units/mg sample) activity varied significantly (P ≤ 0.05). The chickpea-based snack product had intermediate-moisture (23.31% to 27.81%), was low in lipids (5.09% to 5.84%), free of antinutrients, and was a good source of proteins (12.45% to 14.10%), carbohydrates (51.86% to54.96%), and minerals (1.53% to 2.43%). The L^* , a^* , and b^* values of the products ranged from 75.97 to 79.38, 3.46 to 4.75, and 27.65 to 34.65, respectively. The hardness, springiness, and fracturability of the product were 700.89 to 955.23 g, 43.38% to 47.14%, and 5.26 to 5.90 mm, respectively. PRACTICAL APPLICATION: Development of new bean-based products, such as a chickpea-based snack with an overall good nutrition and taste, may play an important role in increasing the consumption of underutilized dry beans in the United States, shown to promote better health and wellness.

Nutraceutical protein isolate from pigeon pea (Cajanus cajan) milling waste by-product: functional aspects and digestibility

The aim of the present study was to utilize the protein from pigeon pea milling waste by-product for the preparation of protein isolate (PPI).