Optimization of lentil protein extraction and the influence of process pH on protein structure and functionality

Comprehensive review of emerging analytical methods for pea protein structure analysis: Advances and implications for food science over the last five years

This review explores recent advancements in analytical techniques for characterizing pea protein structure. With growing interest in sustainable protein sources, understanding the relationship between pea protein's structure and its functionality has become essential. This review covers a range of methods used to assess the structural properties of pea protein, focusing on the impact of environmental and processing conditions, as well as interactions with other materials, including mid-infrared spectroscopy, fluorescence spectroscopy, nuclear magnetic resonance spectroscopy, scanning electron microscopy, X-ray methods and calorimetric methods. By elucidating these methods, detailed insights into pea protein's structural and conformational properties as well as its dynamics are provided, contributing to enhance their potential applications. Thus, a comprehensive overview of commonly used analytical techniques for pea protein structure characterization in its different organization levels, aiming to offer readers an understanding of these techniques and highlight their relevance in selecting the most suitable method for analyzing complex matrices.

Improving the structure of lentil proteins during fermentation and their association with nutritional values and solubility

Lentil proteins (LPs) may encounter challenges in their food industry applications due to certain limitations in their functional properties. This study focused on enhancing the quality of LPs through physical modifications and investigating the effects of a 24-hr fermentation process with Lactiplantibacillus plantarum. The protein structures of LPs were analysed using several techniques, including ultraviolet spectra, fluorescence spectra, and FT-IR spectra, respectively, resulting in the protein structure of LPs substantial modifications (p < 0.05) during the fermentation procedure. protein surface properties of fermented LPs, including surface charge and surface hydrophobicity, changed significantly (p < 0.05) from -23.03 to -32.70 mV and 860.30 to 600.6 a.u., respectively. Using Lactobacillus by fermentation processes can offer several benefits, particularly in enhancing the digestibility, protein structure, and nutritional values of LPs.

Optimization of extraction for efficient recovery of kenaf seed protein isolates: evaluation of physicochemical and techno-functional characteristics

BACKGROUND

Kenaf seeds are a rich source of protein; however, finding the best extraction method is crucial to obtaining high-quality protein from these underutilized seeds. This research devised an optimized extraction process for best recovery of kenaf seeds protein using response surface methodology. The key parameters affecting the yield and protein content were optimized, including extraction pH (2-11), seed:water ratio (5:1-50:1), temperature (30-90 °C), and duration (20-360 min). The physicochemical and techno-functional properties of kenaf seed protein isolates (KSPIs) were examined.

RESULTS

A maximum protein yield of 12.05 g/100 g with purity level 91.94 g/100 g was obtained using an optimized extraction with pH 11.0, seed:water ratio 50:1, 360 min duration, and temperature 50 °C. The oil and water retention capacities of KSPI were 1.14 mL g-1 and 1.37 mL g-1 respectively. After 30 min at pH 7, KSPIs demonstrated remarkable emulsion capacity (83.12%) and stability (75.63%), along with high foaming capacity (106%) and stability (18.3%). As per high-performance liquid chromatography analysis, arginine, glutamic acid, leucine, phenylalanine, and lysine were the most abundant amino acids detected in KPSIs. The KSPIs' globular protein structure was successfully verified using analytical approaches, including Fourier transform infrared spectroscopy, protein fraction ratios, and differential scanning calorimetry. Sodium dodecyl sulfate polyacrylamide gel electrophoresis analysis revealed that KPSI has a molecular weight distribution ranging from 10 kDa to 50 kDa.

CONCLUSION

The results of this study support the application of the proposed response-surface-methodology-optimized extraction method for efficient recovery of high-quality kenaf seed proteins that meet the necessary physicochemical and techno-functional requirements. © 2024 Society of Chemical Industry.

Unravelling the Digestibility and Structure-Function Relationship of Lentil Protein Through Germination and Molecular Weight Fractionation

This study explores for the first time the impact of a 6-day germination process on the structure (FTIR), antioxidant activity, nutritional/safety attributes (ACE-I inhibitory activity, digestibility, and cytotoxicity), and functional properties of fractions of variable molecular weight (W > 5 kDa; 3 kDa < MW < 5 kDa; and MW < 3 kDa) isolated from proteins extracted from lentils. FTIR results indicated a substantial increase in β-sheet contents during germination. The digestibility of proteins increased from day 0 (16.32-17.04%) to day 6 of germination (24.92-26.05%) with variable levels of digestibility depending on their MW. ACE-I inhibitory activity improved during germination in all fractions, reaching IC50 values of 0.95, 0.83, and 0.69 mg/mL after 6 days of germination. All antioxidant activities analyzed notably increased, particularly in low-MW fractions (MW < 3 kDa). The functional properties of low-MW fractions were also the most promising, displaying the highest water and fat binding capacities and emulsifying and foaming capacities but lower foaming and emulsifying stability compared to high-MW fractions. Cytotoxicity tests on L929 cells revealed the slight adverse effects of low-MW fractions during germination. This study provides insights into the enhanced nutritional and functional attributes of lentil proteins following germination, emphasizing their potential application in functional foods.

Transforming plant proteins into plant-based meat alternatives: challenges and future scope

The global transition towards sustainable living has led to a growing demand for innovative food products that enhance environmental sustainability. Traditional meat production is known for its high energy consumption and significant carbon emissions, necessitating alternative approaches. Plant-based meat (PBM) offers a promising solution to reduce the ecological footprint of animal agriculture. This paper examines various challenges in PBM development, including nutritional equivalence, industrial scalability, organoleptic properties, and digestibility. Addressing these challenges requires interdisciplinary collaboration to ensure consumer acceptance, regulatory compliance, and environmental stewardship. Advanced technologies like nanotechnology, fermentation, and enzymatic hydrolysis, along with automation and repurposing cattle farms, offer solutions to enhance PBM's quality and production efficiency. By integrating these innovations, PBM has the potential to revolutionize the food industry, offering sustainable and nutritious alternatives that meet global dietary needs while significantly reducing environmental impact.

Graphical abstract

Lentil protein and trehalose conjugates: Structural interactions and mechanisms for improving multi-level structure and functional characteristics

This study aimed to improve lentil proteins' (LPs) functionality and nutritional value, specifically addressing their lower water solubility and digestibility. A unique combination of LP-disaccharide interactions was employed. Spectroscopic technologies, which include fluorescence spectra, ultraviolet spectra, and Fourier-transform infrared, investigated the structure of LPs at various concentrations of trehalose. The results indicate that the LP structures and conformation were considerably modified (p < 0.05) following trehalose conjugation. The surface charge and hydrophobicity of the trehalose-conjugated LPs (T-LPs) were significantly altered (p < 0.05), from -22.7 to -31.4 and 753 and 543 a.u., respectively. Furthermore, the digestibility and solubility of T-LPs increased from 75% to 81.8% and 60% to 66%, respectively. In conclusion, this study showed that combining LPs and trehalose conjugation could improve the quality of conjugates LPs, which could expand their use in manufacturing as the acceptance of plant-based diets increases. PRACTICAL APPLICATION: Currently, lentil proteins (LPs) are used in plant-based protein powders and supplements. Though less popular than soy or pea proteins, LPs are valued for their high protein content and good amino acid profile. LPs are utilized in meat alternatives and high-protein snack products. The application of these products is mainly due to their nutritional benefits rather than functional properties due to their poor water solubility. Increasing the water solubility of LPs could significantly expand their application in various food industries, making LPs a more competitive and functional plant-based protein source. Trehalose-conjugated LPs with better water solubility allow LPs to be used in other food products, such as plant-based protein beverages. Better solubility would enhance the clarity and smoothness of these products, making them more appealing to consumers.

Unlocking the biorefinery approaches to valorize sugar beet leaves (B. Vulgaris L.) for food industry applications: A critical review

The large-scale cultivation of sugar beets generates a significant amount of by-products, particularly leaves, which are often overlooked and wasted. However, these by-products are a valuable source of functional compounds that can be repurposed to enhance crop sustainability and produce food ingredients. Therefore, valorization of sugar beet leaves (SBLs) is a prudent biorefinery approach for future utilization. This literature review highlights the significant advances in valorizing SBLs for food industry applications. The extractable phytochemical compounds, the sustainability and challenges of recovery, the extraction methods, potential health benefits, current applications, and prospective valorization possibilities of SBLs within a circular economy framework were reviewed. The results showed that SBLs are rich in nutrients and bioactive phytochemicals such as polyphenols (e.g., flavonoids and phenolic acids), proteins, essential amino acids, chlorophylls, fiber, and essential fatty acids. The application of these compounds in the development of food products may exhibit numerous health benefits, including antioxidant, anti-microbial, anti-inflammatory, anti-diabetic, and anti-cancer properties. However, for potential applications of SBLs in the food industry to develop functional foods, nutritional supplements, and natural food additives, further research is needed to optimize the efficient extraction of functional compounds on an industrial scale and to verify the safety of extracted compounds for human consumption.

Preparation and nutritional characterisation of protein concentrate prepared from foxtail millet (Setaria italica)

Plant-based protein sources as a sustainable alternative to animal sources are highly relevant for food and dietary supplements industries. Plant proteins are becoming popular as an eco-friendly source for meeting global protein requirements due to their importance in nutrition, management of metabolic diseases, biological activities, functionality in processed food products and their low carbon footprints. We applied biochemical protein extraction protocol and prepared protein concentrate from an underutilised cereal, foxtail millet, with plausible applications in foods and supplements. Herein efforts were utilised to obtain foxtail millet protein (FMP) concentrate by means of standardisation of processes of extraction cum isolation. The conditions including flour to solvent ratio, extraction-precipitation pH, dissolution time, etc. were optimised to significantly improve protein yield and recovery. The FMP concentrate prepared was also analysed for nutritional composition, bioactive compounds, amino acid content and digestion properties in comparison to packaged brown rice protein concentrate. The protein concentrate prepared was found to have high digestibility, rich in essential amino acids with good phenolic and flavonoid content, thereby making it a potential sensory and antioxidant additive for food/pharmaceutical applications.

Purification and Characterization of Pinto Bean Protein Using Membrane Technology

Pinto beans, an underutilized legume, are abundant in protein content and contain a variety of beneficial phytonutrients. However, the commonly used protein extraction method, alkaline extraction, is associated with several drawbacks. These drawbacks include low extraction yield and purity as well as the production of large amounts of wastewater that can lead to environmental hazards. In this regard, membrane technology has gained considerable recognition as a superior method for extracting proteins. A combined processing scheme was developed, which included alkaline extraction at pH 10.5, ultrafiltration with a concentration factor of 5.5, diafiltration with a diavolume of 4, and isoelectric precipitation at pH 4.5 followed by freeze drying. The specific functional characteristics (nitrogen solubility index, water and oil holding capacity, and emulsifying and foaming properties) of the protein concentrates were assessed and compared with those of a commercially available soybean protein isolate. Based on pinto bean flour containing 23.9% protein, 85.5% of the protein was recovered in the products of this process: precipitated protein concentrate (PPC) with 86.4% protein, acid-soluble protein concentrate (ASP-C) with 56.3% protein, and meal residue with 6.1% protein. The mass yields were 17.3% in PPC, 3.9% in ASP-C, and 54% in the meal residue. The precipitated protein showed higher emulsifying activity, and the acid-soluble protein showed a high nitrogen solubility index (NSI) and oil-holding capacity. Both proteins had comparable foaming properties to commercial soy protein isolate. The project demonstrated the feasibility of protein production from pinto beans and highlighted the proteins' useful food functionality and good potential for commercialization.

Minimizing anti-nutritional factors in wet protein extraction from Swedish faba beans through the application of response surface methodology

Faba beans, rich in protein and ideal for Swedish cultivation, are limited in food industry use due to anti-nutritional factors (ANFs) that hinder nutrient absorption. An extraction method was developed in our study to mitigate ANFs in faba beans, using aqueous alkaline methods and isoelectric precipitation with differential salt concentration. This method yielded 15.8 g of protein per 100 g of flour, with a protein concentration exceeding 83% of the total extract. It reduced ANFs like phytic acid (28.0%), lectins (87.5%), vicine (98.5%), and convicine (99.7%). Extraction conditions were optimized using response surface methodology, identifying pH 6, 2 h, and 20 °C as the most effective parameters, achieving an 86% reduction in phytic acid, closely matched the model's predictions (R2 = 0.945). This method effectively reduced ANFs, offering a sustainable approach for producing proteins suitable for diverse food products, including plant-based alternatives.

Impact of Reconstitution Conditions on the Solubility of Faba Bean Protein Isolate

Faba bean protein isolate (FBPI) is emerging as a promising protein ingredient in the food industry. However, a lack of comprehensive scientific understanding of its functional properties, particularly solubility, limits broader application. This study investigated the reconstitution behaviour of FBPI under different conditions. For this purpose, FBPI dispersions (5% w/w protein) were prepared with varying pH (6.8 or 7.5), temperature (15, 40, or 65 °C), duration of stirring (30, 60, or 90 min), stirring intensity (1000 or 1500 rpm), and water hardness (0, 200, or 400 ppm). Low reconstitution temperature resulted in greater particle size and lower solubility, while elevated temperature minimised intermolecular attractions, improving solubility. Higher pH increased the net-negative charge and thus enhanced the repulsion between the proteins, leading to greater solubility. Water hardness was another important parameter, as greater hardness generally resulted in greater particle size and lower solubility, likely due to calcium bridging. The selection of conditions for the hydration of faba bean protein isolate is important to produce high-quality and high-stability suspensions.

Mild extraction of faba bean (Vicia faba L.) proteins against conventional methods: Impact on physicochemical and thermal characteristics

Faba bean (high- and low-tannin) protein isolates were water extracted followed by dialysis or micellization in comparison to concentrates from conventional alkali extraction + acid precipitation, and salt-based extraction (1% NaCl) + dialysis. Protein fractions were characterised for secondary structure conformational changes, crystalline structure, particle size distribution in aqueous suspension and thermal properties. Mild water or salt extraction did not influence particle size distribution. Based on XRD, FTIR and CD, β-sheet structures were the most abundant secondary structures and water extraction + dialysis had minimal impact on their native conformation. DSC results showed an association between protein purity, glass transition temperature and endothermic enthalpy. High melting temperature above glass transition confirms the suitability of faba bean proteins for thermal/extrusion processing. Fractionation method was a more significant determinant of physicochemical characteristics compared to the cultivar. Further exploration of the techno-functional characteristics of faba bean proteins is essential for value-added food applications.

A comprehensive review of processing, functionality, and potential applications of lentil proteins in the food industry

There is a pressing need for sustainable sources of proteins to address the escalating food demands of the expanding global population, without damaging the environment. Lentil proteins offer a more sustainable alternative to animal-derived proteins (such as those from meat, fish, eggs, or milk). They are abundant, affordable, protein rich, nutritious, and functional, which makes them highly appealing as ingredients in the food, personal care, cosmetics, pharmaceutical and other industries. In this article, the chemical composition, nutritional value, and techno-functional properties of lentil proteins are reviewed. Then, recent advances on the extraction, purification, and modification of lentil proteins are summarized. Hurdles to the widespread utilization of lentil proteins in the food industry are highlighted, along with potential strategies to surmount these challenges. Finally, the potential applications of lentil protein in foods and beverages are discussed. The intention of this article is to offer an up-to-date overview of research on lentil proteins, addressing gaps in the knowledge related to their potential nutritional benefits and functional advantages for application within the food industry. This includes exploring the utilization of lentil proteins as nanocarriers for bioactive compounds, emulsifiers, edible inks for 3D food printing, meat analogs, and components of biodegradable packaging.

Replacing the animal fat in Bologna sausages using high internal phase emulsion stabilized with lentil protein isolate (Lens culinaris)

High internal phase emulsions (HIPEs) are promising techniques that can replace saturated fat in food without reducing the product's texture, sensory attributes, water-holding capacity, and cooking loss. In the current investigation, 100% pork back fat was replaced by HIPEs formed with lentil protein isolate (LPI) in Bologna sausages. HIPEs were prepared by 25% LPI dispersion (2, 4, 6, and 8%, w/w) and 75% (w/w) soybean oil. HIPEs with higher LPI concentration (4, 6, and 8%, w/w) showed lower droplet size, firmer appearance, and better rheology behavior than 2% LPI. The concentrations LPI (2%, 4%, 6%, and 8%, w/w) led to increased moisture in sausages (FH2, FH4, FH6, and FH8, respectively) compared to the FC. These LPI levels resulted in sausage values for pressed juice similar to the FC and lower energy values than sausages with soybean oil (FO) and pork back fat (FC). Besides, these LPI concentrations (4%, 6%, and 8%, w/w) resulted in a lower oil oxidation level in sausages with HIPEs (FH4, FH6, and FH8, respectively) compared to the control sausage formulation with pork back fat (FC). Bologna sausages elaborated with HIPEs showed emulsion stability values higher than 97%, without significance difference between them. The texture and sensory properties of sausages made with HIPEs were comparable to those made with pork back fat. HIPEs may improve the oxidation stability of the Bologna sausages. These results highlight the effectiveness of HIPEs structured with lentil protein in successfully substituting pork back fat in Bologna sausages with a better nutritional appeal.

Impact of pH on the structure, interfacial and foaming properties of pea protein isolate: Investigation of the structure - Function relationship

This study explored the relationship between pea protein foaming properties and their structure and physicochemical properties under neutral and acidic pH. Results showed that pH modified the zeta potential, particle size and surface tension due to electrostatic changes. FT-MIR and fluorescence spectra revealed pH-induced conformational changes, exposing hydrophobic groups and increasing sulfhydryl content, promoting protein aggregation. At pH 3, the highest foaming capacity (1.273) and lowest foam expansion (6.967) were observed, associated with increased surface hydrophobicity and net charges, ideal for creating light foams with high liquid incorporation for acidic beverages or fruit-based mousses. Pea protein isolate generated stable foams with foam volume stability between 86.662 % and 94.255 %. Although neutral pH conditions showed the highest foam volume stability, their air bubbles increased in size and transitioned from spherical to polyhedral shape, suitable for visual-centric applications, like cappuccino foam and beer-head retention. Foams at pH 5 exhibited the smallest bubbles and maintained their spherical shape, enhancing drainage resistance, beneficial for whipped toppings. Strong correlations (Pearson correlation coefficient higher than 0.600) were noted between the structure, surface and foaming properties, providing crucial insights into optimizing pea protein functionality across various pH conditions, enabling the development of plant-based foamed products with tailored properties.

Response surface methodology guided approach for optimization of protein isolate from Faba bean. Part 1/2

Ultrasound-assisted extraction (UAE) was evaluated as a green procedure to produce faba beans protein isolates from faba beans. Magnetic stirring was performed as conventional extraction. A three-level five-factor Box-Behnken Design (BBD) was applied to obtain the optimal UAE conditions to concurrently maximize extraction yield and protein content. The response surface methodology (RSM) showed a quadratic curvature for extraction yield and protein. The optimal extraction conditions were determined as: Power of 123 W, solute/solvent ratio of 0.06 (1:15 g/mL), sonication time of 41 min, and total volume of 623 mL with a desirability value of 0.82. Under these conditions, the extraction yield of 19. 75 ± 0.87 % (Protein yield of 67.84 %) and protein content of 92.87 ± 0.53 % were obtained for optimum ultrasound extraction. Control samples using magnetic stirring under similar conditions without ultrasound treatment showed an extraction yield of 16.41 ± 0.02 % (Protein yield of 54.65 %) and a protein content of 89. 88 ± 0.40 %. This shows that BBD can effectively be used to optimize the extraction of proteins from faba beans using optimal extraction conditions, resulting in a higher extraction yield and protein purity.

Safflower protein as a potential plant protein powder: optimization of extraction and spray-drying process parameters and determination of physicochemical and functional properties

BACKGROUND

The research about sustainable and alternative plant protein sources has accelerated with the increasing need for protein. Safflower meal has a potential to be used in protein production due to its high protein content. This research aimed to produce an alternative plant-based protein powder using safflower meal. Both extraction and spray-drying parameters of safflower protein powder production were optimized using response surface methodology to achieve maximum yield. Moreover, the physicochemical and functional properties of safflower protein were determined and compared with those of commercial protein powders (soy, sunflower, pea, fava bean, and rice).

RESULTS

The optimum extraction conditions were found to be 33.06:1 mL-1 g solvent-to-meal ratio, pH 11.00, 23.34 °C extraction temperature, and 30.86 min extraction time, which were achieved with a protein yield response of 75.21%. The highest powder yield (51.28%) was recorded for drying conditions of inlet air temperature of 160.11 °C, aspiration rate of 54.17 m3 h-1, and feed flow rate of 16.01 mL min-1. According to the amino acid profile of safflower protein, the glutamic acid content (14 475 mg (100 g)-1) was highest, while the methionine content (96 mg (100 g)-1) was lowest. Moreover, safflower protein can be regarded as a high-quality protein due to its high essential amino acid ratio (41.55%). The experiments showed that safflower protein had high solubility and good foam and emulsifying properties.

CONCLUSION

Safflower protein could be a nutritional and functional protein source for the food industry. © 2024 Society of Chemical Industry.

Physicochemical Properties, Functionalities, and Antioxidant Activity of Protein Extracts from New Zealand Wild Sea Cucumbers (Australostichopus mollis)

This study investigated the physicochemical properties, functionalities, and antioxidant capacities of protein extracts from wild sea cucumber Australostichopus mollis collected from four distinct locations in New Zealand. Protein was extracted from sea cucumber body walls using trypsin enzymatic extraction, followed by cold acetone precipitation. The amino acid analysis revealed high glycine (189.08 mg/g), glutamic acid (119.45 mg/g), and aspartic acid (91.91 mg/g) concentrations in all samples. The essential amino acid indexes of the protein extracts (62.96, average) were higher than the WHO/FAO standard references, indicating the excellent protein quality of A. mollis. Furthermore, protein extracts from A. mollis demonstrated superior emulsifying activity (202.3-349.5 m2/g average) compared to commercial soy and whey protein isolates under all tested pH conditions, and enhanced foaming capacity (109.9-126.4%) and stability (52.7-72%) in neutral and acidic conditions. The extracts also exhibited good solubility, exceeding 70% across pH 3-11. Antioxidant capacities (ABTS and DPPH free radical scavenging activity and ferric reducing antioxidant power) were identified in A. mollis protein extracts for the first time, with clear variations observed among different locations. These findings elucidate the advantageous functional properties of protein extracts from wild New Zealand A. mollis and highlight their potential application as high-quality antioxidant food ingredients.

Processing parameters, techno-functional properties and potential food application of lentil protein concentrate as an ingredient for the plant-based market

Lentil (Lens culinaris) is a protein-rich legume consumed worldwide and it also has the potential to become an alternative source of protein ingredient for human nutrition. The aim of this study was to determine the best processing parameters for the whole grain protein wet extraction, as well as to analyze the techno-functional properties, and physical characteristics of the protein concentrate and its flour. It was also evaluated the application of the concentrate into a fish-like croquette. The processing route was carried out by alkaline extraction and acid precipitation of the proteins where the pH, stirring time and solute:solvent ratio were evaluated. The final dried protein concentrate presented 85% protein on dry basis and a mass yield of 14%. The results were reproducible when tested on a first scaling up test. For the techno-functional properties, solubility, water and oil retention capacities, emulsification and foaming capacities and stability, and gelling capacity were tested. As for the food application into fish-like croquettes, the lentil protein showed similar scores for sensory acceptance, flavor and texture when compared to a commercial clean-taste concentrate. The results observed in this study were compatible to other alternative pulse-protein ingredients on the market, positioning lentil protein as a promising alternative protein source to produce ingredients for the plant-based market.

Effects of Alkaline Extraction pH on Amino Acid Compositions, Protein Secondary Structures, Thermal Stability, and Functionalities of Brewer's Spent Grain Proteins

A high alkaline pH was previously demonstrated to enhance the extraction yield of brewer's spent grains (BSG) proteins. The effects of extraction pH beyond the extraction yield, however, has not been investigated before. The present work examined the effects of extraction pH (pH 8-12) on BSG proteins' (1) amino acid compositions, (2) secondary structures, (3) thermal stability, and (4) functionalities (i.e., water/oil holding capacity, emulsifying, and foaming properties). The ideal extraction temperature (60 °C) and BSG-to-solvent ratio (1:20 w/v) for maximizing the extraction yield were first determined to set the conditions for the pH effect study. The results showed that a higher extraction pH led to more balanced compositions between hydrophilic and hydrophobic amino acids and higher proportions of random coils structures indicating increased protein unfolding. This led to superior emulsifying properties of the extracted proteins with more than twofold improvement between pH 8 and a pH larger than 10. The extraction pH, nevertheless, had minimal impact on the water/oil holding capacity, foaming properties, and thermal denaturation propensity of the proteins. The present work demonstrated that a high alkaline pH at pH 11-12 was indeed ideal for both maximizing the extraction yield (37-46 wt.%) and proteins' functionalities.

Lentil protein isolate (Lens culinaris) subjected to ultrasound treatment combined or not with heat-treatment: structural characterization and ability to stabilize high internal phase emulsions

This study evaluated the effect of ultrasound treatment combined or not with heat treatment applied to lentil protein isolate (LPI) aiming to enhance its ability to stabilize high internal phase emulsions (HIPE). LPI dispersion (2%, w/w) was ultrasound-treated at 60% (UA) and 70% (UB) amplitude for 7 min; these samples were subjected to and then heat treatments at 70 °C (UAT70 and UBT70, respectively) or 80 °C (UAT80 and UBT80, respectively) for 20 min. HIPEs were produced with 25% untreated and treated LPI dispersions and 75% soybean oil using a rotor-stator (15,500 rpm/1 min). The LPI dispersions were evaluated for particle size, solubility, differential scanning calorimetry, electrophoresis, secondary structure estimation (circular dichroism and FT-IR), intrinsic fluorescence, surface hydrophobicity, and free sulfhydryl groups content. The HIPEs were evaluated for droplet size, morphology, rheology, centrifugal stability, and the Turbiscan test. Ultrasound treatment decreased LPI dispersions' particle size (∼80%) and increased solubility (∼90%). Intrinsic fluorescence and surface hydrophobicity confirmed LPI modification due to the exposure to hydrophobic patches. The combination of ultrasound and heat treatments resulted in a reduction in the free sulfhydryl group content of LPI. HIPEs produced with ultrasound-heat-treated LPI had a lower droplet size distribution mode, greater oil retention values in the HIPE structure (> 98%), lower Turbiscan stability index (< 2), and a firmer and more homogeneous appearance compared to HIPE produced with untreated LPI, indicating higher stability for the HIPEs stabilized by treated LPI. Therefore, combining ultrasound and heat treatments could be an effective method for the functional modification of lentil proteins, allowing their application as HIPE emulsifiers.

Conjugation of gum Arabic and lentil protein hydrolysates through Maillard reaction: Antioxidant activity, volatile compounds, functional and sensory properties

Lentil protein hydrolysates (LPH) and lentil protein hydrolysates cross-linked (LPHC) were grafted with gum Arabic (GA) through a wet Maillard reaction at 100°C for 2 h and called MLPH and MLPHC. The samples were assessed for absorption, degree of grafting (DG), surface hydrophobicity, antioxidant activity, molecular weight (MW) profile, chemical alteration, volatile compounds, functional and sensory properties. Results showed that Maillard grafting led to increase in absorption and DG (maximum value: MLPHC), and led to the reduction of the surface hydrophobicity and antioxidant activity (minimum value: MLPHC). MW profiles indicated that MLPH and MLPHC formed new bands at MW >250 kDa. Regarding the Fourier transform infrared spectroscopy (FTIR), Maillard conjugation led to the occurrence of peaks at 1759 and 1765 cm-1, while the intensities of amide I bands at 1637 and 1659 cm-1 and amide II bands at 1498 and 1495 cm-1 were decreased. Hydrolysis, cross-linking, and especially Maillard grafting provided well-balanced content of volatile components. Indeed, the proportions of alcohols, ketones, aldehydes, and acids were changed, thereby, the inherent grassy and planty tastes were diminished while new umami taste was developed. Maillard grafting led to significant improvement of functional properties, while MLPH and MLPHC indicated the highest emulsifying activity at pH 10.0 (73.76 and 70.12 m2/g, respectively) and stability (369.64 and 288.22 min), foaming capacity (88.57% and 142.86%) and stability (60.57% and 72%). Sensory analysis has demonstrated that umami taste was highly developed in MLPH and MLPHC, which can be well considered as meat proteins and flavor enhancers such as monosodium glutamate (MSG).

Isolation of detoxified cassava (Manihot esculenta L.) leaf protein by alkaline extraction-isoelectric precipitation: Optimization and its characterization

The cassava leaves protein isolate extraction and optimization were investigated using response surface methodology, where the maximum protein content (21.83 ± 0.41 g/100 g dm), extraction yield (18.31 ± 0.53%), and protein recovery yield (69 ± 1.31%) were obtained at optimal conditions: 114 min extraction time, 46 °C extraction temperature, 23.5 mL/g solvent/solute ratio and pH 11.0 value. The presence of toxicant (Cyanide) and anti-nutrient (tannin) in cassava leaves reduced the bio-accessibility of its protein isolate, strictly prohibiting its consumption. Therefore, detoxification was applied to diminish cyanide and tannin to 85% and 69% in leaves, respectively, where the protein content was reduced to 9.7%. However, detoxified cassava leaf protein isolate exhibited changes in the compositional, structural, morphological, molecular, and thermal characteristics compared to the controlled one. Moreover, the functional properties in protein isolate improved after detoxification at different pH conditions, which can be used as an active ingredient in various foods.

Health-promoting benefits of lentils: Anti-inflammatory and anti-microbial effects

This paper describes how lentils (Lens culinaris species) can positively affect health by reducing inflammation, providing antioxidants, and displaying antimicrobial properties. Lentils are rich in proteins, essential amino acids, minerals, and fibers, making them a valuable source of nutrition, particularly in low and middle-income countries. Lentils have many health benefits, including positive effects on diabetes management, support for cardiovascular health, and antioxidative properties. The antioxidative properties of lentils, attributed to their phenolic content, and their ability to inhibit inflammation-related enzymes are also discussed. We discuss the potential of lentils as a dietary tool in promoting immunity, reducing disease burdens, and preventing nutritional deficiencies. Overall, lentils are a highly nutritious food with various health benefits, including anti-inflammatory and antimicrobial effects. The fiber and protein content in lentils make them beneficial for weight management, blood sugar regulation, and supporting overall gut health. Furthermore, the slow rate at which lentils affect blood sugar levels, due to their low glycemic index, can be advantageous for individuals with diabetes.

Alu'datt M, R. Al Qudsi F, Tan TC, A. Razzak Mahmood A, Maghaydah S. Molecular forces driving protein complexation of lentil and whey proteins: Structure-function relationships of trehalose-conjugated protein complexes on protein digestibility and solubility

Plant-based proteins are often associated with a range of health benefits. Most research primarily investigates pea and soy proteins, while lentil proteins received minimal attention. This study evaluates the effect of protein complexation (using the pH-shifting technique) coupled with trehalose conjugation on lentil and whey proteins. The protein structures after the modification were analysed using spectroscopic methods: Fourier-transform infrared, ultraviolet spectra, and fluorescence spectra. The amide group I, conformation protein, and tertiary structure of the trehalose-conjugated lentil-whey protein complexes (T-LWPs) showed significant changes (P < 0.05). Moreover, the surface properties (surface hydrophobicity and charges) of T-LWPs were significantly modified (P < 0.05), from 457 to 324 a.u and from 36 to -40 mV, respectively. Due to these modifications on the protein structures, the protein digestibility (80-86%) and water solubility (90-94.5%) of T-LWPs increased significantly (P < 0.05) with the increase in the trehalose concentration, from 0 (control) to 5% (w/w), respectively. This study suggested that coupling protein complexation and trehalose conjugation can enhance the overall properties of lentil-based protein complexes. With this enhancement, more opportunities in the utilisation of lentils are to be expected.

The influence of thermodynamic qualities of a solvent on the physicochemical properties of lentil protein concentrate - Second virial coefficient study

A protein concentrate (75.2%) was obtained from some Lens culinaris L. seeds. The osmotic, hydrodynamic and surface properties of protein concentrate aqueous solutions were studied with the help of membrane osmometry, dynamic light scattering, ζ-potential and the pendant drop method, in a wide range of protein concentrate concentrations and pH conditions. The second virial coefficient was determined in the range of pH 2-9. Two theta points (pH∼ 5 and pH∼ 8) were found. The change of the hydrodynamic radii as a function of pH and scattering vector was analysed. It was found that the change of the solvent parameters (pH) has a significant influence on the surface tension value. This phenomenon was related to the values of the second virial coefficient and the translational diffusion coefficient. The increase in the value of the diffusion coefficient (smaller hydrodynamic radius) resulted in faster interface formation at the gas-liquid interface.

Thermo-induced changes in the structure of lentil protein isolate (Lens culinaris) to stabilize high internal phase emulsions

This study aims to assess the impact of heat treatment on the emulsifying properties of lentil protein isolate (LPI) dispersion to produce high internal phase emulsions (HIPEs). The heat-treated LPI dispersion was characterized by size, turbidity, solubility, zeta potential, free sulfhydryl group, electrophoresis, differential scanning calorimetry, circular dichroism, Fourier transforms infrared spectroscopy and intrinsic fluorescence. HIPEs were produced with 25% of LPI dispersion (2%, w/w) and soybean oil (75%) using a rotor-stator (15,500 rpm/1 min). HIPEs were evaluated for their droplet size, zeta potential, centrifugal stability, microscopy, appearance, Turbiscan stability, and rheology over 60 days (25 °C). Heat treatment reduced the size of LPI, resulting in increased turbidity, solubility, and exposure of hydrophobic groups. HIPEs produced with heat-treated LPI at 70 °C (HIPE70) and 80 °C (HIPE80) for 20 min exhibited lower droplet sizes, increased stability, reduced oil loss, and a homogeneous appearance compared to HIPE produced with untreated LPI (HIPEc). In addition, HIPE70 and HIPE80 displayed resistance to shear stress, higher apparent viscosity, and increased storage modulus than HIPEc. HIPEs produced with heat-treated LPI were stable, suggesting that the treatment was efficient for improving the functional properties of the protein and the possibility of future research focusing on fat substitutes in food applications.

Characterization of Proteins Extracted from Ulva sp., Padina sp., and Laurencia sp. Macroalgae Using Green Technology: Effect of In Vitro Digestion on Antioxidant and ACE-I Inhibitory Activity

Macroalgal proteins were extracted from Ulva rigida (URPE) (green), Padina pavonica (PPPE) (brown), and Laurencia obtusa (LOPE) (red) using ultrasound-assisted enzymatic extraction, which is one of the green extraction technologies. Techno-functional, characteristic, and digestibility properties, and biological activities including antioxidant (AOA) and angiotensin-I converting enzyme (ACE-I) inhibitory activities were also investigated. According to the results, the extraction yield (EY) (94.74%) was detected in the extraction of L. obtusa, followed by U. rigida and P. pavonica. PPPE showed the highest ACE-I inhibitory activity before in vitro digestion. In contrast to PPPE, LOPE (20.90 ± 0.00%) and URPE (20.20 ± 0.00%) showed higher ACE-I inhibitory activity after in vitro digestion. The highest total phenolic content (TPC) (77.86 ± 1.00 mg GAE/g) was determined in LOPE. On the other hand, the highest AOACUPRAC (74.69 ± 1.78 mg TE/g) and AOAABTS (251.29 ± 5.0 mg TE/g) were detected in PPPE. After in vitro digestion, LOPE had the highest TPC (22.11 ± 2.18 mg GAE/g), AOACUPRAC (8.41 ± 0.06 mg TE/g), and AOAABTS (88.32 ± 0.65 mg TE/g) (p < 0.05). In vitro protein digestibility of three macroalgal protein extracts ranged from 84.35 ± 2.01% to 94.09 ± 0.00% (p < 0.05). Three macroalgae showed high oil holding capacity (OHC), especially PPPE (410.13 ± 16.37%) (p < 0.05), but they showed minimum foaming and emulsifying properties. The quality of the extracted macroalgal proteins was assessed using FTIR, SDS-PAGE, and DSC analyses. According to our findings, the method applied for macroalgal protein extraction could have a potential the promise of ultrasonication application as an environmentally friendly technology for food industry. Moreover, URPE, PPPE, and LOPE from sustainable sources may be attractive in terms of nourishment for people because of their digestibility, antioxidant properties, and ACE-I inhibitory activities.

Effects of slit dual-frequency ultrasound-assisted pulping on the structure, functional properties and antioxidant activity of Lycium barbarum proteins and in situ real-time monitoring process

To improve the protein dissolution rate and the quality of fresh Lycium barbarum pulp (LBP), we optimized the slit dual-frequency ultrasound-assisted pulping process, explored the dissolution kinetics of Lycium barbarum protein (LBPr), and established a near-infrared spectroscopy in situ real-time monitoring model for LBPr dissolution through spectral information analysis and chemometric methods. The results showed that under optimal conditions (dual-frequency 28-33 kHz, 300 W, 31 min, 40 °C, interval ratio 5:2 s/s), ultrasonic treatment not only significantly increased LBPr dissolution rate (increased by 71.48 %, p < 0.05), improved other nutrient contents and color, but also reduced the protein particle size, changed the amino acid composition ratio and protein structure, and increased the surface hydrophobicity, zeta potential, and free sulfhydryl content of protein, as well as the antioxidant activity of LBPr. In addition, ultrasonication significantly improved the functional properties of the protein, including thermal stability, foaming, emulsification and oil absorption capacity. Furthermore, the real-time monitoring model of the dissolution process was able to quantitatively predict the dissolution rate of LBPr with good calibration and prediction performance (Rc = 0.9835, RMSECV = 2.174, Rp = 0.9841, RMSEP = 1.206). These findings indicated that dual-frequency ultrasound has great potential to improve the quality of LBP and may provide a theoretical basis for the establishment of an intelligent control system in the industrialized production of LBP and the functional development of LBPr.

Extraction methods and nutritional characterization of protein concentrates obtained from bean, chickpea, and corn discard grains

Protein concentrates obtained from discarded grain flours of white chickpea Sinaloa (Cicer arietinum) (CC), "Azufrazin" bean (Phaseolus vulgaris) (BC), and white corn (Zea mays) (MC), were characterized biochemically through bromatological analyses (protein, lipid, fiber, moisture, ashes, and nitrogen free extract), HPLC techniques (amino acids content), and spectrophotometry (anti-nutrients: phytic acid, trypsin inhibitors, and saponins). The percentage of protein obtained from CC, BC, and MC was 71.23, 81.10, and 55.69%, respectively. Most peptides in the BC and CC flours had a molecular weight of <1.35 kDa, meanwhile, MC peptides were heavier (1.35 to 17 kDa). The amino acids (AA) profile of flours and protein concentrates were similar; however, all the protein concentrates showed an increased AA accumulation (300 to -400%) compared with their flours. The protein concentrates from BC registered the highest AA accumulation (77.4 g of AA/100 g of protein concentrates). Except for the phytic acid in CC and trypsin inhibitor in CC and MC, respectively, the rest of the protein concentrates exhibited higher amounts of the anti-nutrients compared with their flours; however, these levels do not exceed the reported toxicity for some animals, mainly when used in combination with other ingredients for feed formulations. It is concluded that CC and BC protein concentrates showed better nutritional characteristics than MC (level of protein, size of peptides, and AA profile). After biochemical characterization, protein concentrates derived from by-products have nutritional potential for the animal feed industry.

Effects of processing technologies on the antioxidant properties of common bean (Phaseolus vulgaris L.) and lentil (Lens culinaris) proteins and their hydrolysates

The effects of ultrasound (280 W, 5 min), heat treatment (75 °C and 90 °C for 10 min) and microfluidization (125 MPa, 4 cycles) as pre or post treatments and their combination with enzymatic hydrolysis on the antioxidant properties of common bean and lentil protein hydrolysates were investigated. In general, hydrolysis resulted in increases of antioxidant activity, both in the presence and absence of processing technologies. The increases reached maximum values of 158% (ABTS), 105% (DPPH), 279% (FRAP) and 107% (TAC) for the bean protein hydrolysates submitted to post-treatment with ultrasound (ABTS, FRAP and TAC) and pre-treatment with microfluidization (DPPH), compared to their respective controls (untreated samples). For lentil proteins, the increases reached 197% (ABTS), 170% (DPPH), 690% (FRAP) and 213% (TAC) for samples submitted to ultrasound post-treatment (ABTS), microfluidization pre-treatment (DPPH) and post-treatment (FRAP), and 75 °C pre-treatment (TAC) compared to their respective controls. Surface hydrophobicity and molecular weight profile by SEC-HPLC analysis indicated modifications in the structures of proteins in function of the different processing technologies. For both proteins, electrophoresis indicated a similar profile for all hydrolysates, regardless of the process applied as pre or post treatment. Solubility of bean and lentil protein concentrates was also improved. These results indicated that different processing technologies can be successfully used in association with enzymatic hydrolysis to improve the antioxidant properties of lentil and bean proteins.

Enhanced stabilization of oil-in-water (O/W) emulsions by fibrillar gel particles from lentil proteins

Pulse proteins as a sustainable protein source have attracted increasing interest in food development, but pulse proteins are generally less surface active than dairy proteins. This work introduces lentil protein (LP)-based fibrillar gel particles (FGPs) fabricated from heat-induced LP fibrillar aggregates by 1, 4, 8, and 16 h of heating, followed by particle reduction using sonication. The heating time significantly impacts the FGPs particle size and surface hydrophobicity. The FGP prepared by 4 h of heating (FGP-4) showed a small size (<200 nm) and homogeneous size distribution while possessing significantly increased surface hydrophobicity compared to untreated LP. Such structural features made FGP-4 better adsorb at the O/W interface and then completely covered the oil droplet surface, leading to homogeneous emulsions of small size (22.33 μm) and superior long-term stability without creaming for 30 days. In addition, the dispersed FGP in the bulk phase could develop interactions among each other, leading to improved emulsion viscosity and texture without oil droplet size change. This finding suggests that constructing fibril-type gel particles can provide a new strategy for forming superior O/W emulsions with improved stability from plant proteins.

A Study on a Polymeric Foam Based on Pulse Proteins and Cellulose Fibrils

Biofoams are a challenge for scientists in terms of innovation. Incorporation of cellulose fibrils (CF), might help improve the microstructure of foams, thus this study focuses on studying the impact of CF on the foaming properties and rheology of lentil protein (LP) foams at various pH and CF concentrations. Additionally, LP-CF mixtures were transformed into solid foams, and their microstructure, physical properties, and morphology were evaluated. CF concentration significantly impacted on LP-CF foam properties, primarily due to high viscosity values. Increased CF concentration resulted in improved FS values (up to 77 min) at all pH values. This is likely attributed to associative interactions and coacervates formation. Also, foam microstructure could be related to apparent viscosity, suggesting the role of viscosity in preserving the integrity of the wet foam structure during freezing and lyophilization processes. However, elevated viscosity values might negatively impact properties such as foaming capacity and produce denser microstructures. The microstructure and morphology analysis revealed that certain foams exhibited a sponge-like structure with open pores and semi-spherical shapes, supported by CF fibers extending and forming layers. However, the structure itself was irregular. While others exhibited non-uniform, irregular pore size, and shape, along with a denser structure. These findings contribute to understanding the behavior of LP-CF mixtures, although additional investigations on mechanical properties, biodegradability, and hydrophobicity are necessary to reach their full potential for various applications.

Green leaf proteins: a sustainable source of edible plant-based proteins

The rise in the global population, which is projected to reach 9.7 billion by 2050, has resulted in an increased demand for proteins in the human diet. The green leaves of many plants are an affordable, abundant, and sustainable source of proteins suitable for human consumption. This article reviews the various sources of green leaf proteins that may play an important role in alleviating global malnutrition, including those from alfalfa, amaranth, cabbage, cassava, duckweed, moringa, olive, radish, spinach, sugar beet, and tea. The structure of green leaves and the location of the proteins within these leaves are described, as well as methods for extracting and purifying these proteins. The composition, nutritional profile, and functional attributes of green leaf proteins are then discussed. The potential advantages and disadvantages of using green leaf proteins as functional food ingredients are highlighted. The importance of obtaining a better understanding of the composition and structure of different green leaves and the proteins extracted from them is highlighted. This includes an assessment of non-protein nitrogen and anti-nutritional compounds that may be present. Furthermore, the impact of isolation and purification techniques on the functionality of the plant protein ingredients obtained must be carefully evaluated.

Comparative study on molecular and higher-order structures of legume seed protein isolates: Lentil, mungbean and yellow pea

Lentils and mungbean proteins are under-researched compared to pea and soybean. Lentils (green, red and black-lentils), mungbean and yellow pea protein isolates were obtained by alkaline extraction (pH 9)-isoelectric precipitation (pH 4.5) and investigated for molecular and higher-order structures using complementary and novel approaches. These extracted isolates showed comparable protein content but significantly greater nitrogen solubility index (NSI > 85 %) than commercial pea and soy protein isolates (NSI < 60 %). Based on molecular weight estimations from sodium dodecyl sulphate-polyacrylamide gel electrophoresis analysis, the soluble proteins of lentils and yellow pea were identified as legumin-like and vicilin-like, while mungbean was dominated by vicilin-like proteins. The soluble extracts were confirmed to be in native structural condition by size exclusion chromatography and nano-differential scanning calorimetry, unlike commercial extracts. Further differences in secondary structure were evident on circular dichroism spectra of the soluble extracts and deconvolution of the Amide I region (1700-1600 cm-1) from Fourier Transform Infrared of the total protein.

Protein composition of pulses and their protein isolates from different sources and in different isolation pH values using a reverse phase high performance liquid chromatography method

The objective of this study was to compare the composition of pulse proteins isolated from lentils and green and yellow peas at two isolation pH values (9 and 11) and determine the effect of this variability on protein functionality. Chromatogram peaks obtained from reverse-phase high performance liquid chromatography were identified by isolation of albumin-, vicilin- and legumin-rich fractions for the three pulses. Protein composition was obtained for each isolate and compared against that of the originating pulse flour. Lentil flour showed the highest level of vicilin with a vicilin/legumin ratio of ∼ 2.5, while this ratio was 1.3 and 1.2 for green and yellow pea flour, respectively. Albumin content of yellow pea flour was high (∼36.1 %), which reduced to ∼ 15-19 % in isolated proteins showing a loss in albumins during the isolation. Higher extraction pH increased pea protein yield but led to lower protein solubility with no changes in foaming properties and in-vitro digestibility.

The effect of alkaline extraction and drying techniques on the physicochemical, structural properties and functionality of rice bran protein concentrates

Rice bran protein concentrates (RBPC) were extracted using mild alkaline solvents (pH: 8, 9, 10). The physicochemical, thermal, functional, and structural aspects of freeze-drying (FD) and spray-drying (SD) were compared. FD and SD of RBPC had porous and grooved surfaces, with FD having non-collapsed plates and SD being spherical. Alkaline extraction increases FD's protein concentration and browning, whereas SD inhibits browning. According to amino acid profiling, RBPC-FD9's extraction optimizes and preserves amino acids. A tremendous particle size difference was prominent in FD, thermally stable at a minimal maximum of 92 °C. Increased pH extraction gives FD greater exposal surface hydrophobicity and positively relates to denaturation enthalpy. Mild pH extraction and drying significantly impacted solubility, improved emulsion properties, and foaming properties of RBPC as observed in acidic, neutral, and alkaline environments. RBPC-FD9 and RBPC-SD10 extracts exhibit outstanding foaming and emulsion activity in all pH conditions, respectively. Appropriate drying selection, RBPC-FD or SD potentially employed as foaming/emulsifier agent or meat analog.

Effects of tea saponin on the foaming properties of pea protein

Plant proteins are becoming increasingly important for foam formation as an alternative to animal proteins. Consumers, however, are unsatisfied with the foaming properties of pea protein isolates. Recent research on proteins and surfactants has primarily concentrated on chemically synthesized surfactants. In this study, foams were prepared by complexing pea protein isolates with a natural small molecule surfactant tea saponin. This study investigates the mechanisms responsible for the formation and stability of foams prepared from pea protein isolates (PPIs) complexed with tea saponins. Analyses of foaming performance were carried out by analyzing the morphology of foam, foaming properties, foam's rheological properties, and the microstructure of the pea protein-tea saponin complex system. Compared to the pea protein isolate alone, the pea protein-tea saponin complex significantly improved foaming capacity and foaming stability. As shown by light microscopy analysis, the size of the foam decreased and became more homogeneous, probably because of the altered aggregate state of the protein. In this study, natural surfactants and mixtures of plant proteins are studied in order to better understand their properties. The mixed system has excellent prospects for application in the industries related to foam.

Optimization of Soybean Protein Extraction with Ammonium Hydroxide (NH4OH) Using Response Surface Methodology

Plants have been recognized as renewable and sustainable sources of proteins. However, plant protein extraction is challenged by the plant's recalcitrant cell wall. The conventional extraction methods make use of non-reusable strong alkali chemicals in protein-denaturing extraction conditions. In this study, soy protein was extracted using NH4OH, a weak, recoverable, and reusable alkali. The extraction conditions were optimized using response surface methodology (RSM). A central composite design (CCD) with four independent variables: temperature (25, 40, 55, 70, and 85 °C); NH4OH concentration (0.5, 1, and 1.5%); extraction time (6, 12, 18, and 24 h) and solvent ratio (1:5, 1:10, 1:15 and 1:20 w/v) were used to study the response variables (protein yield and amine concentration). Amine concentration indicates the extent of protein hydrolysis. The RSM model equation for the independent and response variables was computed and used to create the contour plots. A predicted yield of 64.89% protein and 0.19 mM amine revealed a multiple R-squared value of 0.83 and 0.78, respectively. The optimum conditions to obtain the maximum protein yield (65.66%) with the least amine concentration (0.14 Mm) were obtained with 0.5% NH4OH concentration, 12 h extraction time, and a 1:10 (w/v) solvent ratio at 52.5 °C. The findings suggest that NH4OH is suitable to extract soybean protein with little or no impact on protein denaturation.

Associated Changes in the Structural and Antioxidant Activity of Myofibrillar Proteins via Interaction of Polyphenolic Compounds and Protein Extracted from Lentil (Lens culinaris)

This study evaluated the effects of different concentrations of green lentil acetone extract (GLA) (250, 500, 750, and 1000 μg/mL) and protein of green lentil (PGL) (1, 2, 3, and 4 g/100 g MP) on the functional attributes of myofibrillar protein (MP). GLA extract and PGL significantly affected the structure of MP by decreasing the carbonyl and sulfhydryl contents. Intrinsic fluorescence quenching studies showed that static quenching was involved in MP-GLA extract and MP-PGL complexes. Compared to the control (MP), the addition of GLA extract and PGL decreased the surface hydrophobicity, which correlated with the decrease in protein solubility. The MP-GLA and MP-PGL had lower cooking losses and slightly higher water-holding capacities $\left(P<0.05\right)$ . FTIR spectroscopy demonstrated changes in MP secondary structure with the addition of GLA extract and PGL. GLA extract and PGL also decreased the thermal stability of MP and showed significant synergism in enhancing the radical scavenging activity of MP. Taken together, the results indicated that a high concentration of GLA extract (1000 μg/mL) and PGL (4 g/100 g MP) improved the functional properties of MP, and GLA extract was the most effective.

Effect of protein-starch interactions on starch retrogradation and implications for food product quality

Starch retrogradation is a consequential part of food processing that greatly impacts the texture and acceptability of products containing both starch and proteins, but the effect of proteins on starch retrogradation has only recently been explored. With the increased popularity of plant-based proteins in recent years, incorporation of proteins into starch-based products is more commonplace. These formulation changes may have unforeseen effects on ingredient functionality and sensory outcomes of starch-containing products during storage, which makes the investigation of protein-starch interactions and subsequent impact on starch retrogradation and product quality essential. Protein can inhibit or promote starch retrogradation based on its exposed residues. Charged residues promote charge-dipole interactions between starch-bound phosphate and protein, hydrophobic groups restrict amylose release and reassociation, while hydrophilic groups impact water/molecular mobility. Covalent bonds (disulfide linkages) formed between proteins may enhance starch retrogradation, while glycosidic bonds formed between starch and protein during high-temperature processing may limit starch retrogradation. With these protein-starch interactions in mind, products can be formulated with proteins that enhance or delay textural changes in starch-containing products. Future work to understand the impact of starch-protein interactions on retrogradation should focus on integrating the fields of proteomics and carbohydrate chemistry. This interdisciplinary approach should result in better methods to characterize mechanisms of interaction between starch and proteins to optimize their food applications. This review provides useful interpretations of current literature characterizing the mechanistic effect of protein on starch retrogradation.

Improving the Functionality of Lentil–Casein Protein Complexes through Structural Interactions and Water Kefir-Assisted Fermentation

Highly nutritious lentil proteins (LP) have recently attracted interest in the food industry. However, due to their low solubility, extensive application of LP is severely limited. This study describes a new and successful method for overcoming this challenge by improving the nutritional–functional properties of LP, particularly their solubility and protein quality. By combining protein complexation with water kefir-assisted fermentation, the water solubility of native LP (~58%) increases to over 86% upon the formation of lentil–casein protein complexes (LCPC). Meanwhile, the surface charge increases to over −40 mV, accompanied by alterations in secondary and tertiary structures, as shown by Fourier-transform infrared and UV-vis spectra, respectively. In addition, subjecting the novel LCPC to fermentation increases the protein digestibility from 76% to over 86%, due to the reduction in micronutrients that have some degree of restriction with respect to protein digestibility. This approach could be an effective and practical way of altering plant-based proteins.

Impact of ultrasound processing on alternative protein systems: Protein extraction, nutritional effects and associated challenges

Proteins from alternative sources including terrestrial and aquatic plants, microbes and insects are being increasingly explored to combat the dietary, environmental and ethical challenges linked primarily to conventional sources of protein, mainly meat and dairy proteins. Ultrasound (US) technologies have emerged as a clean, green and efficient methods for the extraction of proteins from alternative sources compared to conventional methods. However, the application of US can also lead to modifications of the proteins extracted from alternative sources, including changes in their nutritional quality (protein content, amino acid composition, protein digestibility, anti-nutritional factors) and allergenicity, as well as damage of the compounds associated with an increased degradation resulting from extreme US processing conditions. This work aims to summarise the main advances in US equipment currently available to date, including the main US parameters and their effects on the extraction of protein from alternative sources, as well as the studies available on the effects of US processing on the nutritional value, allergenicity and degradation damage of these alternative protein ingredients. The main research gaps identified in this work and future challenges associated to the widespread application of US and their scale-up to industry operations are also covered in detail.

Extraction Optimization, Functional and Thermal Properties of Protein from Cherimoya Seed as an Unexploited By-Product

Plant-based proteins are gaining in attraction compared with animal-based proteins due to their superior ethical profiles, growing concerns on the part of various organizations about animal health and welfare, and increased global greenhouse-gas emissions in meat production. In this study, the response surface methodology (RSM) using a Box-Behnken design (BBD) was applied to optimize the ultrasound-assisted alkaline extraction of cherimoya-seed proteins as valuable by-products. The effects of three pH, temperature, and time factors on the protein-extraction yield and protein content were investigated. The pH at 10.5 and temperature of 41.8 °C for 26.1 min were considered the optimal ultrasound-assisted alkaline-extraction conditions since they provided the maximum extraction yield (17.3%) and protein content (65.6%). An established extraction technique was employed to enhance the cherimoya-seed protein yield, purity, and functional properties. A thermogravimetric analysis (TGA) of the samples showed that the ultrasound-assisted alkaline extraction improved the thermal stability of the protein concentrate.