Lentil Protein Research Articles

Mechanisms of molecular and structural interactions between lentil and quinoa proteins in aqueous solutions induced by pH recycling

SummaryThere has been a growing interest in plant proteins due to their beneficial health effects, low cost and variety of applications in food industries. The low solubility of lentil proteins (LPs) is one of the significant factors that limit their use in food applications. Quinoa proteins (QPs), which have high water solubility, were combined with LPs at pH 12 to generate LP‐QP complexes to generate pH‐based soluble protein compounds. The LP‐QP complexes demonstrated a large surface charge with an increase solubilisation of the protein complexes by more than 85%, together with resistance to protein aggregation. The combination of LPs to QPs led to a significant increase (P < 0.05) in unique tertiary and secondary protein structures as determined by the protein–protein interaction (PPI) technique involving pH recycling. Interactions between LPs and QPs affected the surface morphology of the protein complexes formed. Electrostatic interactions, hydrophobic forces and hydrogen bonding were indicated to play key roles in the PPIs. The capacity of pH cycling to illustrate the above protein interactions shows that this is a robust approach for assessing the emulsion and foaming properties of food proteins.

Emulsifying properties of lentil protein preparations obtained by dry fractionation

Dry fractionated legume protein ingredients are gaining attention as alternatives to conventional solvent extracted legume proteins, being more resource efficient and often exhibiting novel functional properties. However, lack of knowledge about the relationship between composition and functionality limit a more wide-spread use of dry-fractionated legume protein in applications. In this study, lentil fractions of different degrees of refinement were prepared using air classification having protein and starch contents of 16–59% and 4–64%, respectively. The dry fractionated lentil fractions could emulsify and stabilize 10 wt% oil-in-water emulsions, while a conventional lentil protein isolate used for comparison was not able to form stable emulsions. The latter had significantly larger mean droplet diameters (around 20 µm) due to droplet flocculation than emulsions made with the different lentil fractions ranging between 0.3 and 5.5 µm. Similar surface charges (between −22 and −31 mV) indicated that the discrepancy could be ascribed to differences in steric repulsion and mechanical strength of the interfacial layers between conventionally and dry fractionated lentil. Storage stability tests of emulsions stabilized with dry fractionated samples resulted in separation into a low and higher density phase with the individual droplets being stable against coalescence in both phases. The phase separation was attributed to gravimetrical sedimentation of larger insoluble components accumulating in the denser phase, which was impacted by the degree of refinement by air classification. The results highlight the potential of dry fractionation for the production of sustainable ingredients with unique composition and functionality.

Mechanism, kinetics, and physicochemical properties of ultrasound-produced emulsions stabilized by lentil protein: a non-dairy alternative in food systems

Mechanism, kinetics, and physicochemical properties of ultrasound-produced emulsions stabilized by lentil protein: a non-dairy alternative in food systems

PSV-11 The effects of pelleting and extrusion on nutrient composition and protein quality measurements in a variety Canadian pulses

Abstract Alternative forms of protein are an important focus in nutrition. This study sought to compare the effects of pelleting and extrusion on nutrient composition and protein quality measurements of Canadian pulses. Pulses used for the study included: 2 pea variety (Amarillo and dunn), lentils, chickpeas, and faba bean. Ingredients were ground through a 10/64” or a 2/64” screen to create a coarse and fine ground product, respectively. Both coarse and fine ground ingredients were pelleted at 60–65, 70–75, and 80–85 C0. Fine ground ingredients were extruded at three different temperatures (110, 130, 150 C0) and two moisture levels (18 and 22%). Samples were collected for all runs at the beginning, middle, and end of each run for both pelleted and extruded samples. Samples were analyzed for proximate analysis, amino acids including lysinoalanine, total and damaged starch, and total dietary fibre (including insoluble and soluble). Data were analyzed using a mixed model via proc glimmix in SAS, where ingredient, process, grind, temperature, and extrusion moisture were treated as fixed effects with different interactions selected based on model investigated. Crude protein content of whole pulses was highest in faba bean and lowest in the Amarillo pea, with faba bean protein content significantly higher than all other pulses, and lentil protein content significantly higher than Amarillo peas (P < 0.05). All pelleting temperatures, nested within grind, significantly increased crude protein content of all pulses compared to whole pulses (P < 0.05). All extrusion moistures significantly increased crude protein content of all pulses compared to whole pulses (P < 0.05) and moisture/temperature interactions were significantly higher for all pulses compared to whole pulses (P < 0.05). Amino acid comparisons produced similar significant results. This suggests that pelleting and extrusion processing can have a positive impact on protein content of pulses and protein quality measurements in pulses.

Characterization of bioactive peptides produced from green lentil ( Lens culinaris ) seed protein concentrate using Alcalase and Flavourzyme in single and sequential hydrolysis

This study aimed to produce bioactive peptides with increased angiotensin-converting enzyme (ACE)-inhibitory and antioxidant activities from single and sequential hydrolysis, using Alcalase and Flavourzyme at the enzyme to substrate ratio of 2% and hydrolysis time of 180 min. Results indicated that sequential hydrolysis led to a higher degree of hydrolysis (DH) value (47.05%) compared with single hydrolysis (8.51% and 20.12%). Higher ACE-inhibitory activity and total phenol content were determined for the lentil protein hydrolysates (LPH) compared with lentil protein concentrate, and also higher antioxidant activity was obtained comparing with butylated hydroxytoluene as a synthetic antioxidant. The main amino acid profile of hydrolysates was maintained. The higher DH via hydrolysis was obtained, more small and medium molecular weight peptides were generated according to the gel permeation chromatography and sodium dodecyl sulfate–polyacrylamide gel electrophoresis. Hydrolysis did not have a significant effect on the denaturation point of protein, and thus the thermal stability was maintained. Shorter peaks were observed for hydrolysates by atomic force microscopy. Enzymatic hydrolysis increased the umami sensorial taste. Novelty impact statement Using a combination of enzymes in sequential hydrolysis can produce bioactive peptides with improved ACE-inhibitory and antioxidant activities. Alcalase leads to the production of bitter taste peptides which can be altered by applying Flavourzyme to hydrolyze the former peptides to fewer bitter peptides. Lentil protein was hydrolyzed sequentially into bioactive peptides with improved anti-hypertensive and antioxidant activities and increment of umami taste in respect to the produced peptides with specific amino acid profiles.

Effects of red lentil protein addition on textural quality and starch digestibility of brown rice noodles

SummaryIn this study, the additions of red lentil, rice protein and lentil protein on the quality of brown rice (BR) noodles were investigated, aiming to develop nutritionally fortified noodles with both desirable textural quality and lower starch digestibility. The results showed that the additives reduced the hardness, cohesiveness and chewiness, and increased cooking loss and turbidity of rice noodles. The addition of lentil protein had less effect on the texture quality of rice noodles when compared with the red lentil and rice protein. Lentil protein decreased the starch digestibility of BR noodles, thereby reducing the estimated glycemic index (eGI) from 70.48 to 65.33. XRD and FTIR revealed that lentil protein increased the relative crystallinity and 1047/1022 cm−1 ratio. Ordered structure could effectively limit the interaction between amylase and starch, and reduce its digestibility. Therefore, lentil protein was more suitable to be added in BR noodles to reduce starch digestibility.

β-Glucan Interaction with Lentil (Lens culinaris) and Yellow Pea (Pisum sativum) Proteins Suppresses Their In Vitro Digestibility.

In this study, β-glucan interaction with lentil and yellow pea proteins and the effect on in vitro protein digestibility were investigated. Proteins were mixed with β-glucan at mass ratios of 1:0.5, 1:1, and 1:2. The interaction between β-glucan and the proteins was demonstrated by the decrease in transmittance and surface charge and the increase in particle size of the complexes. Bright-field microscopy showed the formation of aggregates between the biopolymers, although increased molecular size was not observed by discontinuous native polyacrylamide gel electrophoresis. Fluorescence microscopy indicated that β-glucan formed aggregates with lentil proteins, while the interaction with yellow pea proteins appeared as distinct phases of protein within the β-glucan network. The in vitro protein digestibility of lentil and pea protein decreased by 27.3 and 34.5%, respectively, in the presence of a β-glucan mass ratio of 1:2. The findings confirm the possibility to modulate protein digestibility by changing the physical characteristics of a food matrix.

Effect of High Pressure Processing and heat treatment on in vitro digestibility and trypsin inhibitor activity in lentil and faba bean protein concentrates

This study investigated the effects of HPP and heat treatment on digestibility and trypsin inhibitor activity in lentil protein concentrate (LPC) and faba bean protein concentrate (FPC). LPC and FPC with 15 g protein/100 g were treated with HPP (600 MPa/5 °C/4 min) or heat (95 °C/15 min), then subjected to in vitro digestion. Digesta were analyzed by SDS-PAGE for hydrolyzed protein fraction patterns and their concentrations. The concentration of peptides and free amino acids was also determined. The effect of HPP and heat treatment on trypsin inhibitor activity was determined for 5 g protein/100 g LPC and FPC. HPP and heat treatments led to different hydrolyzed peptide patterns after gastric digestion. HPP resulted in comparable or greater gastric digestibility than untreated controls, but higher gastric proteolysis than heat treatment. Neither treatment impacted overall in vitro protein digestibility, for either LPC or FPC. HPP slightly reduced trypsin inhibitor activity (~8% for LPC, ~6% for FPC), while heat treatment led to much greater reductions (86% for LPC, ~78% for FPC) than untreated controls. Overall, HPP and heat treatment did not negatively impact lentil and faba bean protein quality, which is useful information for developing new food product applications.

Interaction of lentil protein and onion skin phenolics: Effects on functional properties of proteins and in vitro gastrointestinal digestibility

The effect of protein–phenolic interactions on the functional properties of lentil protein and in vitro gastrointestinal digestibility in different systems (extract solution, protein–phenolic solution, and emulsion) was studied. The presence of phenolic compounds negatively affected the foaming and emulsion properties of lentil protein. During in vitro gastrointestinal digestion, total phenolic content (TPC) and antioxidant capacity of the samples were decreased with the presence of lentil protein at the initial phase, however, they were found to be the highest in emulsions at the intestinal phase. The amount of protocatechuic acid and phenolic acid derivative was increased at the intestinal phase, while that of other phenolic compounds was decreased. Quercetin was not detected at the intestinal phase in all systems, while its glycoside derivatives were determined, which were the highest in emulsions. Anthocyanins were also the highest in extract solution among all systems. Protein–phenolic interactions had a significant effect on functional properties of lentil proteins, and bioaccessibility or antioxidant capacity of phenolic compounds.

Life cycle assessment of animal‐based foods and plant‐based protein‐rich alternatives: an environmental perspective

In the European Union proteins for food are largely animal based, consisting of meat and dairy products. Almost all soy but also a larger part of pulses and cereals consumed in the European Union are used for animal nutrition. While livestock is an important source of proteins, it also creates substantial environmental impacts. The food and feed system is closely linked to the planetary and health boundaries and a transformation to healthy diets will require substantial dietary shifts towards healthy foods, such as nuts, fruits, vegetables and legumes. Extrudated vegetable meat alternatives consisting of protein combined with amaranth or buckwheat flour and a vegetable milk alternative made from lentil proteins were shown to have the potential to generate significantly less environmental impact than their animal-based counterparts in most of the environmental indicators examined, taking into account both functional units (mass and protein content). The underlying field-to-fork life cycle assessment models include several variants for both plant and animal foods. The optimized plant-based foods show a clear potential for improvement in the environmental footprints. Development of higher processed and therefore higher performing products is crucial for appealing to potential user groups beyond dedicated vegetarians and vegans and ultimately achieving market expansion. The Protein2Food project showed that prototypes made from European-grown legumes and pseudocereals are a valuable source for high-quality protein foods, and despite being substantially processed they could help reduce the environmental impact of food consumption. © 2021 Society of Chemical Industry.

Nutritional and Rheological Features of Lentil Protein Isolate for Yoghurt-Like Application.

The substitution of animal protein with proteins of plant origin is a viable way to decrease the negative impact caused by animal husbandry on the environment. Pulse consumption has been widely promoted as a nutritious contribution to protein supplementation. In this study, an emulsion of lentil (Lens culinaris) protein isolate is fermented with lactic acid bacteria (LAB) to manufacture a yoghurt alternative and the techno-functional properties compared to a dairy- and a soy-based product with similar protein contents. The yoghurt-like products are subjected to large and small deformation analysis, quantification of fermentable oligosaccharides, disaccharides, monosaccharides and polyols (FODMAP), water holding capacity tests, protein profile analysis and the gel structure is visualised by confocal laser scanning microscopy (CLSM). The lentil yoghurt alternative shows good water holding capacity, high firmness and consistency values in large deformation analysis, with cohesiveness and viscosity not significantly different from that of dairy yoghurt. The high gel strength and rigidity of the lentil yoghurt gels measured by small deformation analysis is well-reflected in the dense protein matrix in the CLSM graphs. FODMAP content of the lentil yoghurt is very low, making it suitable for consumption by irritable bowel syndrome (IBS) patients. Our results show that lentil protein isolate is an excellent base material for producing a plant-based yoghurt alternative.

Generation of bioactive peptides from lentil protein: degree of hydrolysis, antioxidant activity, phenol content, ACE-inhibitory activity, molecular weight, sensory, and functional properties

Generation of bioactive peptides from lentil protein: degree of hydrolysis, antioxidant activity, phenol content, ACE-inhibitory activity, molecular weight, sensory, and functional properties

Effect of biopolymer mixing ratios and aqueous phase conditions on the interfacial and emulsifying properties of lentil protein isolate–κ‐carrageenan and lentil protein isolate–ι‐carrageenan complexes

AbstractBackground and objectivesThe use of plant protein ingredients within the food industry is increasing rapidly due to their lower cost, greater environmental sustainability, perceived safety concerns related to consuming animal products, and consumer dietary preferences. Lentil protein, as an emerging nonsoy, gluten‐free, plant‐based protein, could play more important role in food processing. However, plant proteins generally contribute lower solubility than animal proteins; incorporation of polysaccharides such as carrageenan could tailor the functionality of lentil protein. This work aimed to investigate the complexation behavior between lentil protein isolate (LPI) and carrageenan (κ‐carrageenan: κ‐C and ι‐carrageenan: ι‐C) as a function of pH and biopolymer mixing ratio, and the emulsifying properties of their resulting soluble and insoluble complexes.FindingsIncorporation of both κ‐C and ι‐C into the LPI solution led to the suppression of large protein aggregates being formed during a turbidimetric pH acid titration. As LPI–carrageenan mixing ratio decreased, maximum optical density (max OD) values for both LPI‐κ‐C and LPI‐ι‐C systems decreased. Emulsions made at pH 6 showed higher emulsion stability than those made at pH 3.5 for each sample. Emulsions at pH 6 also formed smaller, more uniform, and higher charged droplets and showed lower interfacial tension. 4:1 LPI‐κ‐C and 4:1 LPI‐ι‐C emulsions at pH 6 showed higher emulsion viscosity and higher corresponding continuous phase viscosity.ConclusionsSoluble and insoluble complexes were formed between LPI and both carrageenan polysaccharides through electrostatic interactions at pH 6 and pH 3.5, respectively. Emulsions prepared at pH 6 showed higher stability than emulsions at pH 3.5, where the highest emulsion stability was contributed to 4:1 LPI‐κ‐C and 4:1 LPI‐ι‐C emulsions.Significance and noveltyLentil protein interacted with carrageenan through electrostatic attraction, where soluble complexes were formed between the positive patches on LPI and negatively charged carrageenan and insoluble complexes were formed between positively charged LPI and negatively charged carrageenan. Both types of electrostatic complexes were used to prepare emulsions, and soluble complexes were shown to contribute better emulsion stability than insoluble complexes. Preparation of the stable LPI–carrageenan‐based emulsion is a low‐cost, nonsolvent, and relatively easy process, which shows potential for further food applications.

Structure – Functionality of lentil protein-polyphenol conjugates

Lentil protein isolate (LPI) was conjugated with plant polyphenols (quercetin, rutin, ellagic acid), and the structural and functional characteristics of the conjugates were determined in comparison with the proteins and pure polyphenols. The interaction between polyphenols and protein was achieved by a grafting method at pH 9.0 in the presence of atmospheric oxygen. Surface plasmon resonance measurements showed polyphenols’ direct interaction with LPI, with the order of binding strength quercetin > ellagic acid > rutin. The degree of conjugation also followed the same order. Structural analysis of the conjugates was performed using FTIR, intrinsic fluorescence, and surface hydrophobicity. A significant improvement in DPPḢ radical scavenging and ferric reducing antioxidant power of the conjugates was observed compared to the polyphenols. However, there was a decrease in the surface activity of the conjugates compared to LPI. Such conjugation provides a novel way to combine the advantages of using plant protein and polyphenols in developing a novel food ingredient.

Long-term stable emulsions prepared from lentil protein fibrillar aggregates

This present study investigated lentil proteins-based aggregates as a stabilizer to form oil-in-water emulsions. Lentil proteins (LP) were heated at neutral and acidic pH to form particulate (pH 7.0) and fibrillar aggregates (pH 2.0). The impacts of aggregate type, protein aggregate concentration, and oil fractions (ϕ) on the emulsion stability were systematically investigated. The results reveal that neither lentil protein solutions nor its particulate aggregates effectively stabilized O/W emulsions, but the LP fibrillar aggregates could form long-term stable emulsions. Due to their elongated structure, fibrillar aggregates may better adsorb and arrange at the oil/water interface to form a strong solid coating to limit coalescence and creaming. The confocal microscopic image revealed that the fibrillar aggregates could be interconnected to form a network in the continuous phase to further stabilize the oil droplets. This research has demonstrated that the construction of fibrillar aggregates can provide a new strategy to form stable plant proteins-based emulsions without using synthetic surfactants. Although the LP fibrillar aggregates were prepared at acidic pH, the suspension could be adjusted to pH 5–7 for effective stabilization of the emulsions against coalescence and creaming, thus allow wide applications in both food and cosmetic formulations.

Beef flavor vegetable hamburger patties with high moisture meat analogs (HMMA) with pulse proteins-peas, lentils, and faba beans.

Pulses have been an excellence source of foods due to their nutritional profile including high protein content. In addition, they have less concerns about allergens, gluten, and genetically modified organisms. In this study, high moisture meat analogs (HMMA) that contained commercial pea protein (55.4% protein), lentil protein (55.4% protein), or faba bean protein (61.5% protein) mixed with other constant ingredients (pea isolates, and wheat gluten and canola oil) were produced using a twin‐screw extruder (TX‐52) with an attached cooling chamber. For consumer sensory tests and texture profile analysis, vegetable hamburger patties with HMMA were produced with the addition of spices, binders, and so on. Trained panelists reported that HMMA with pulses had higher scores on bean‐like, sweet, and cohesiveness of mass compared to HMMA with soy that had higher soy, cardboardy, hardness, and springiness scores. Compared to the control, consumer panelists indicated that samples containing pulse proteins had no differences in consumers’ liking for the cooked appearance and overall flavor, but had a lower overall texture liking score, and samples with faba bean proteins (FP) had a lower overall liking score. Cooked patties containing pulse proteins were redder and had more cooking yield. Patties with FP required less cooking time. Therefore, vegetable patties with pulse proteins are competitive with soy‐based samples.

Effects of Fermentation on the Quality, Structure, and Nonnutritive Contents of Lentil (Lens culinaris) Proteins

Protein digestibility, secondary protein structure components, sugars, and phenolic compounds were analysed to investigate the effect of fermentation on the quality, structure, digestibility, and nonnutritive contents of lentil (Lens culinaris) proteins (LPs). Fermentation was carried out using water kefir seed. The initial pH of the unfermented LPs (6.8) decreased to pH 3.4 at the end of the fermentation on day 5. Protein digestibility increased from 76.4 to 84.1% over the 5 days of fermentation. Total phenolic content increased from 443.4 to 792.6 mg of GAE/100 g after 2 days of fermentation, with the sums of the detected phenolic compounds from HPLC analysis reaching almost 500 mg/100 g. The predominant phenolic compounds detected in fermented LPs include chlorogenic and epicatechin, while traces of rutin, ferulic acid, and sinapic acid were observed. Fermentation played a major role in the changes of the components in the secondary protein structure, especially the percentage of α -helices and random coils. In addition, the reduction in α -helix: β -sheet ratio with the increase in protein digestibility was related to the prolongation of the fermentation time. The model used in this research could be a robust tool for improving protein quality, protein degradation, and nonnutritive nutrients using water kefir seed fermentation.

Parallel comparison of functional and physicochemical properties of common pulse proteins

The demand for more functional plant-based proteins has greatly increased. The objective of this study was to provide a systematic understanding of the functional properties and physicochemical features of protein isolates extracted from common pulses. Chickpea protein (ChPI) was much less soluble compared to other extracted proteins. Pigeon pea protein (PiPI) and lab extracted soybean protein (SPI) possessed excellent emulsification capacity and stability of 0.71–0.73 and 0.70–0.71 cm/cm, respectively. Most proteins had foaming capacities greater than 1.20 mL/mL, except for ChPI. Lentil protein (LPI-W), pea protein, and PiPI showed greater water absorption capacity of 4.9, 3.5, and 3.6 g/g than other proteins and good oil absorption capacity. Pigeon pea protein had the greatest gelation capacity, with a least gelation concentration of 80 g/L. ChPI had a higher thermal denaturation peak temperature (169 °C) than the other proteins (145–154 °C). Commercial SPI was much less functional compared to the lab extracted SPI, which was due to intensive protein denaturation during commercial processing. The amino acid profiles, SDS-PAGE patterns, secondary structure composition, and relative surface hydrophobicity were analyzed to help elucidate the functional features. This study provides useful information in selecting appropriate protein sources to achieve more desirable functional applications.

Formulation, pilot-scale preparation, physicochemical characterization and digestibility of a lentil protein-based model infant formula powder.

Infant formula is a human milk substitute for consumption during the first months of life. The protein component of such products is generally of dairy origin. Alternative sources of protein, such as those of plant origin, are of interest due to dairy allergies, intolerances, and ethical and environmental considerations. Lentils have high levels of protein (20-30%) with a good amino acid profile and functional properties. In this study, a model lentil protein-based formula (LF), in powder format, was produced and compared to two commercial plant-based infant formulae (i.e., soy; SF and rice; RF) in terms of physicochemical properties and digestibility. The macronutrient composition was similar between all the samples; however, RF and SF had larger volume-weighted mean particle diameters (D[4,3] of 121-134 μm) than LF (31.9μm), which was confirmed using scanning electron and confocal laser microscopy. The larger particle sizes of the commercial powders were attributed to their agglomeration during the drying process. Regarding functional properties, the LF showed higher D[4,3] values (17.8μm) after 18 h reconstitution in water, compared with the SF and RF (5.82 and 4.55 μm, respectively), which could be partially attributed to hydrophobic protein-protein interactions. Regarding viscosity at 95 °C and physical stability, LF was more stable than RF. The digestibility analysis showed LF to have similar values (P < 0.05) to the standard SF. These results demonstrated that, from the nutritional and physicochemical perspectives, lentil proteins represent a good alternative to other sources of plant proteins (e.g., soy and rice) in infant nutritional products. © 2021 The Authors. Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Physicochemical and functional properties of red lentil protein isolates from three origins at different pH

Red lentils (Lens culinaris) present an attractive raw material for meat mimics due to its red-coloured proteins, abundance, high protein and low cost. However, data on its functional properties at various pH remain scarce. In this study, the physicochemical and functional properties of red lentil proteins (RLP) from three origins (USA, Nepal and Turkey), isolated by isoelectric precipitation, were evaluated. Amino acid profiles, water holding (ranging from 3.1 to 3.5 g/g) and oil absorption (ranging from 5.8 to 7.3 g/g) capacities of RLP samples were significantly different (p < 0.05). RLP consisted of legumin and vicilin, and comprised predominantly glutamine/glutamic acid (ranging from 8.72 to 10.55 g/100 g). Surface charge, protein solubility, foaming and emulsifying properties were the lowest and poorest at pH 5.2 (isoelectric point). Overall, good functional properties of RLP under high acidity and alkalinity conditions make it a promising protein for mimicking a wide range of meats.