Recent advances in legume protein‐based colloidal systems

Developing nature‐derived surface‐active ingredients with favorable interfacial and functional properties has recently received increasing attention in the food and pharmaceutical industries. Legume proteins are used extensively in food colloidal systems because of their small particle size, high water absorption capability, excellent functional properties (e.g., emulsification, foamability, and gelation), and film formation. There are some limitations in legume proteins, such as high water vapor permeability and fragility, as well as low stability and solubility. Various conventional and innovative processing technologies (e.g., high‐pressure homogenization, ultrasonication, and cold plasma processing) have been successfully employed in order to modify the functional and interfacial properties of legume proteins. In this review, the formation and stability of legume protein‐based colloidal systems and their applications are discussed.

Therefore, the application and development of natural surface-active components by replacing synthetic ones with ones with favorable interfacial and functional properties have become emerging research areas for food manufacturers and researchers.
Among natural biopolymers, proteins play a crucial role in stabilizing colloidal systems due to their amphiphilic nature and excellent interfacial properties, including high adsorption kinetics and surface activities that can effectively cover the surfaces at the water/oil or oil/water interface and reduce the interfacial tensions (Drusch et al., 2021;Mekala et al., 2022a).In this regard, proteins are widely utilized in different food industries, including dairy, baking, confectionary, and beverage, in the form of micro-or nanoparticles as surfactants, stabilizers, and thickening agents (Kim et al., 2020;Ribeiro et al., 2021).The interfacial properties of proteins highly depend on their molecular weight, surface hydrophobicity/hydrophilicity ratio, structure, and amino acid composition, as well as the environmental conditions, such as pH, temperature, concentration, and ionic strength (Gentile, 2020;Hinderink et al., 2021).Previously, the surface properties and mechanisms of animal-based proteins, especially dairy and egg proteins, have been well studied and characterized (Ha et al., 2019;Liu, Oey, et al., 2019).However, a growing number of consumers are interested in adopting vegetarian or vegan diets because of health, environmental, and ethical concerns associated with animal-derived foods (Tarahi, Hedayati, & Shahidi, 2022;Tarahi, Shahidi, & Hedayati, 2022;Zhao, Huang, et al., 2022).Moreover, to overcome the nutritional requirements of the growing global population and to provide sustainable protein sources, plant-based proteins have recently received increasing attention in a wide range of food products with significant consumer acceptability (Hadidi et al., 2022).
Consequently, one of the current hot topics in nutrition and food science is to replace animal-derived proteins with plant ones (e.g., meat analogs), develop foods for special needs (e.g., celiacs), and provide appealing food alternatives (e.g., spreadable gelled food products and nutritionally balanced protein shakes/snacks) on the market.
The plant proteins are isolated from different botanical sources, including legumes (soy, peas, beans, lupins, and lentils), cereals (wheat, corn, rice, oat, barley, and sorghum), pseudo-cereals (quinoa, amaranth, and chia), oilseeds (canola, sunflower, hemp, flax, cotton, and sesame), nuts (peanut, pistachio, almond, walnut, cashew, and hazelnut), green leaves (beet, duckweed, and alfalfa), and many others (mushroom and potato) (Lin & Miao, 2021;Nasrabadi et al., 2021).They can be isolated from food waste and by-products of food processing industries and utilized in the food, drug, and cosmetic sectors as sustainable, inexpensive, high-quality, health beneficial, low-allergenic, and environmentally friendly components (Schmitt et al., 2021;Sharif et al., 2018).Legumes are the richest source of proteins among plant sources, ranging from 20% to 45% (Maphosa & Jideani, 2017).Soy protein isolate (SPI) and pea protein isolate (PPI) are two prominent legume proteins that are widely used in food colloidal systems due to their excellent functional properties, including emulsification, foamability, gelation, and film formation, as well as their small particle size and high water absorption capacity (Chao & Aluko, 2018;Wang et al., 2021).Furthermore, they can be utilized to design the targeted delivery and controlled release of bioactive components (e.g., curcumin, quercetin, lutein, vitamin D 3 , and thymol) (Ashfaq et al., 2022;Mozafarpour, Sani, et al., 2022;Wan et al., 2015).Despite the advantages of legume proteins, they also have some weaknesses, such as high water vapor permeability and fragility due to the presence of many free hydroxyl groups in their molecular structure.In addition, native legume proteins generally have low stability and solubility under harsh processing conditions (extreme pH, temperature, and ionic strength) and at pH near the isoelectric point, which limits their performance as a functional ingredient in food production (Lin & Miao, 2021;Wang et al., 2021).
In order to modify the functional and interfacial properties of legume proteins, various strategies have been employed, including physical processes (e.g., heating, sonication, high-pressure treatments, and cold plasma), chemical processes (e.g., pH adjustment and acylation), enzymatic processes (e.g., hydrolysis and cross-linking), and also a combination of more than one process.Mostly, protein denaturation is induced by those treatments, and the unfolded proteins aggregate through cross-linking interactions, which improve the solubility, gelforming ability, and surface-active properties of the modified proteins (Lin & Miao, 2021;Mozafarpour, Sani, et al., 2022;Zhao, Huang, et al., 2022).This review is focused on the physicochemical and functional properties of legume proteins (e.g., solubility, surface charge and hydrophobicity, particle size, disulfide bonds, and free sulfhydryl) with various modifications and their influence on the interfacial stability of the colloidal systems.

| PHYSICAL MODIFICATIONS
The physical modifications of proteins have recently received much attention among consumers and processors because of their novelty, versatility, automation, and eco-friendly (chemical-free) operations.Some of the important novel (nonthermal) processing technologies that are currently exploited in the textural modification of plant proteins include high-pressure treatment, dielectric-heating, ultrasound (US), pulse electric heating, and ohmic heating.These techniques can change the structure of proteins based on the designer's preference for a specific sensory or texture of food.

| Sonication
Sonication is an innovative, sustainable, and green technology based on cavitation, which occurs with the formation and subsequent collapse of microbubbles in a liquid environment exposed to US waves and generates strong mechanical forces (Mekala et al., 2022a).During the sonication process, strong mechanical forces such as shear force, microscopic turbulence, and shock waves are generated.These forces disrupt the intermolecular hydrogen and hydrophobic interactions, unfold and break down the protein structure, expose the hydrophobic and sulfhydryl groups in the protein, and improve the structural and functional properties of proteins (Mozafarpour, Koocheki, & Nicolai, 2022;Zhang, Liu, et al., 2022).The process produces high temperature and pressure, free radicals, and superoxide by the sudden bursting of microbubbles, which leads to the cross-linking of protein molecules (Bi et al., 2022).
The effects of US treatment on the functional and interfacial properties of legume proteins have been reported in the literature (Table 1).The sonication process can change the secondary structure of proteins and reduce their size.It further extends their techno-functionality, such as molecular flexibility, surface charge, interfacial adsorption, and solubility, leading to better emulsifying ability and stability with smaller oil droplet sizes (Liu, Hu, Du, Liao, et al., 2022;Mozafarpour, Koocheki, & Nicolai, 2022;Mozafarpour, Sani, Koocheki, McClements & Mehr, 2022;Xu et al., 2021;Zhang, Liu, et al., 2022;Zhi et al., 2022).Mekala et al. (2022a) observed larger oil droplets in US-treated lentil protein concentrate (LPC) emulsions.
These findings indicate that sonication can influence protein-based colloidal systems as a function of the type and concentration of proteins and processing conditions.
The emulsion stability of US-treated SPI was examined for targeted intestinal release of lipophilic nutrients by Zhong et al. (2021).
short time.HP processing successfully inactivates pathogens while nutritional and sensory qualities remain unaffected (Mirmoghtadaie et al., 2016).The HP treatment has been successfully used for improving the digestibility, structure, and surface hydrophobicity of proteins by breaking the electrostatic and hydrophobic interactions (Nasrabadi et al., 2021;Sridhar et al., 2022).The change in the protein structure and gelation depend on the type of protein, pressure intensity and cycle, holding time, and process temperature (Table 2).
The effects of HP treatment (100, 200, 300, and 400 MPa, 10 min) on chlorophyll-SPI interactions and functional properties were studied by Cao et al. (2022).By applying the HP, the thermal and color stabilities of chlorophyll and chlorophyll-SPI mixtures increased, in particular at 100 and 200 MPa.The changes in tertiary and quaternary structures of SPI result in an increase in protein surface hydrophobicity and particle size.The largest binding constant (K a ) of SPI was obtained at 100 MPa (≈13.8Â 10 5 L/mol) (Table 2).
T A B L E 2 Effects of different physical treatments on the functional and interfacial properties of legume protein-based colloidal systems
no difference between those ratios.Low ζ-potential values (<À30 mV) indicated formation of a stable emulsion.As emulsifiers, lentil proteins decreased the interfacial tension of the water-oil interphase from 16.5 to <7.0 mN/m, irrespective of pressure levels.
Nanoemulsions exhibited pseudoplastic characteristics, and a higher apparent viscosity was observed with 2:1 ratio.Furthermore, it has been concluded that a stable lentil nanoemulsion can be made by using 1:1 emulsifier to oil ratio and pressurization above 200 MPa with two homogenization passes that could be used as novel food systems.These results suggested that HPH treatment has a good potential to modify the functional and structural properties of legume protein suspensions and produce a stable emulsion.

| Heat treatment
Heat treatments, either conventional heating or innovative heating techniques (e.g., ohmic heating, microwave heating, radio frequency treatment, and infrared irradiation), can modify the physical characteristics of legume proteins.An adequate heating process can lead to the breaking of intramolecular bonds in proteins, loss of their secondary and tertiary structures, and the unfolding and denaturing of the subunits.Finally, proteins reaggregate through new hydrophobic and electrostatic interactions, as well as disulfide and hydrogen bonds, and the buried reactive groups (e.g., hydrophobic and sulfhydryl groups) are getting exposed (Chao & Aluko, 2018;Nasrabadi et al., 2021).It should be mentioned that the proteins' reaggregation does not always lead to the revealing of buried reactive groups.The desired functional properties can be achieved by carefully selecting the protein type and concentration and controlling environmental (pH and ionic concentration) and heating (temperature and time) conditions (Fernando, 2022).Zhao et al. (2020) reported an improvement in the gelling ability, water-holding capacity, and hardness of SPI gel incorporated with soy oil following the thermal denaturation at 90 C for 15 min (Table 2).In another study, Chao and Aluko (2018) evaluated the structural, emulsifying, and foaming properties of PPI in selected thermal processing conditions.The PPI aggregated in the temperature range of 80 to 100 C, and the highest denaturation level was observed at pH 3. The emulsion-forming ability of PPI has been improved by heat treatment, at pH 7, which could be related to their small size emulsified oil droplets.Similarly, higher ESI, surface hydrophobicity, and better gelforming ability were observed in heat-treated faba bean protein isolate (FBPI) (90 C for 5-30 min) (Nivala et al., 2021).

| Cold plasma processing (CPP)
Cold plasma processing (CPP), as a nonthermal, green, and low-cost technique, has recently gained much attention in the food industry due to its ability for food anti-contamination and shelf life extension.
Cold plasma has been employed for the modification of proteins.
Plasma, the fourth state of matter, is composed of a large number of excited ionic, molecular, atomic, and free radical species that can be generated in a wide range of pressures and temperatures by various electrical discharges such as dielectric barrier discharge, corona discharge, micro hollow cathode discharge, gliding arc discharge, radio wave discharge, microwave discharge, and so on (Ekezie et al., 2017;Sharma & Singh, 2022).Some carrier gasses such as air, argon, nitrogen, oxygen, and helium are utilized individually or in combination for producing highly reactive superoxide anion radicals, nitric oxide, hydroperoxyl radicals, and hydroxyl radicals (Basak & Annapure, 2022).These highly reactive species can react with the side chains of aromatic rings of tryptophan, tyrosine, and phenylalanine, as well as sulfur-containing amino acids (methionine and cysteine), which can induce the cleavage of covalent bonds or the initiation of chemical reactions and enhance the structural and technological properties of proteins at micro-to nanometer scales (Mirmoghtadaie et al., 2016;Nasrabadi et al., 2021).
While working on the cold plasma treatment of grass pea protein isolate (GPPI), Mehr andKoocheki (2020, 2021) observed increasing protein solubility with increasing voltage and time.Such an increase was attributed to the increase in surface charge of the protein and reduction in particle size of the protein.Furthermore, they reported that the electrostatic repulsion between protein molecules is the main reason for the solubility of globulins.The application of cold plasma increased the functional and interfacial properties of GPPI, including surface charge and hydrophobicity, carbonyl groups, oxidation efficiency, and disulfide bond contents.However, the process negatively affected the particle size, ζ-potential, solubility, free SH groups, and interfacial tension (Table 2).A similar trend has been reported by Zhang, Huang, et al. (2022) for cold plasma-treated pea protein concentrate (PPC).They observed higher surface hydrophobicity and gel strength, whereas fluorescence intensity, ζ-potential, free SH groups, and solubility were lowered.More research is being conducted to better understand the mechanism of cold plasma on the functionality of legume protein delivery systems.

| CHEMICAL MODIFICATIONS
Chemical modifications (e.g., pH adjustment, acylation, phosphorylation, glycosylation, and deamidation) can be used to achieve changes in the protein structures and functionality.Most of these methods are safe; however, some of them have limitations on regulations and clean labeling for food applications (Nasrabadi et al., 2021).In this section, the effects of pH adjustment and acylation modifications on the physicochemical and interfacial properties of legume proteins are discussed.

| pH adjustment
In the pH adjustment technique, proteins are partially unfolded at extreme alkaline or acidic pH conditions, followed by reassembling by adjusting the pH to the neutral value of 7. The process changes the protein structure from a "globular" to a "melted globular" conformation.This technique makes the protein structures more flexible and improves their functional properties, such as solubility, emulsion stability, and gel-forming ability (Liu, Hu, Du, Liao, et al., 2022;Tang et al., 2021).The modification of modified black turtle bean protein isolates was performed via pH adjustment (pH 1 to 3 for 8 h/adjustment to pH 7.2 for 3 h), which resulted in improvements in their digestibility, fat-holding capacity, and emulsifying and foaming properties (He et al., 2020).Furthermore, the effects of pH adjustment on SPI-based colloidal systems have been reported in several studies.Liu, Hu, Du, Liao, et al. (2022) achieved higher emulsifying activity and stability, solubility, free sulfhydryl content, and surface hydrophobicity for pH-adjusted SPI samples compared to the untreated one.Similar trends were reported for the structural and emulsifying properties of SPI at pH of 3 and 11 (Tan et al., 2021).
While working on pH adjustment of SPI-soy hull polysaccharide complexes (pH 3 to 9), Wang et al. (2020) reported a decrease in the interfacial tension and particle size of emulsions and formed a more uniform structure with higher stability at pH 5. A higher encapsulation efficiency of SPI stabilized with curcumin at a pH in the range of 7 to 8 was also reported Li, Zhang, et al. (2022).

| Acylation
Acylation is defined as the introduction of an acyl group to the amino/hydroxyl groups in amino acid residues by halides and acyl anhydrides, which can be classified into acetylation, succinylation, palmitoylation, and maleylation, based on the selected acylating agent (Fernando, 2022).Among these methods, succinylation is one of the most common strategies to modify the emulsifying ability, solubility, and functional properties of proteins by increasing the net negative charge of the protein, especially at hydroxyl and lysine amino groups (Nasrabadi et al., 2021).Xia et al. (2021) obtained a higher carboxyl content by adding ethylenediaminetetraacetic dianhydride (EDTAD) from 50 to 300 g/kg in acylated SPI (30%-74.07%).They observed a significant increase in ζ-potential, emulsifying activity, and surface hydrophobicity of 68%, 120%, and 213%, respectively, whereas the particle size decreased to 247 nm (from more than 2 μm).In addition, the smallest droplet size of emulsions (10 μm) was attained with the addition of 150 g/kg EDTAD at pH 6.The effect of succinylation and chitosan on the digestibility and stability of SPI-stabilized quercetin emulsions demonstrated that succinylated SPI had a higher shelf life and oxidation stabilities and the bioavailability of quercetin increased significantly from 18.38% to 41.64% (Liu, Hu, Du, Yan, et al., 2022).
These results indicate the potential application of acylation for the encapsulation and delivery of bioactive components and improvement of legume-based emulsion stability.

| ENZYMATIC MODIFICATIONS
Enzymatic modifications are widely used to improve protein functionality at a selected pH and temperature.Both the proteolytic (pepsin, trypsin, bromelain, ficin, etc.) and the non-proteolytic (transglutaminase and laccase) enzymes are used for the purpose.Proteolytic enzymes are used to hydrolyze peptide bonds in a specific amino acid sequence of a protein.Non-proteolytic enzymes can also be capable of modifying the protein structure by forming intermolecular covalent bonds (Fernando, 2022;Nasrabadi et al., 2021).The enzymatic modifications can be classified into enzymatic hydrolysis and enzymatic cross-linking methods.

| Hydrolysis
Enzymatic hydrolysis is a promising technique to improve the emulsifying and antioxidant activities of legume-based proteins in a simple, safe, and economical way.The proteolytic enzymes (proteases) can cleave specific sites on protein molecules and influence both the location and the number of the peptide linkages, which change their conformations based on the enzyme specificity at selected concentration, pH, temperature, ionic strength, and extent of protein denaturation.Proteases influence protein functionality by partially unfolding proteins and decreasing their molecular weight but also by increasing the number of ionizable groups and exposing hydrophobic and other reactive groups (Panyam & Kilara, 1996;Zhao, Zheng, et al., 2022).Shuai et al. (2022) investigated the functional and structural properties of hydrolyzed PPI with four proteases (alcalase, trypsin, flavourzyme, and neutrase) at the various degree of hydrolysis (DH, 2%-8%).
At the 8% DH, the solubility of the trypsin-treated PPI increased significantly from 10.23% to 58.14%.The authors further reported that the proteases could break disulfide bonds, leading to the breakdown of protein moieties into smaller peptides of low molecular weight and converting insoluble fractions into soluble ones.Both the foaming and the emulsifying activities of PPI were improved after enzymatic treatments at below 6% DH.Hao et al. (2022) observed a similar trend for alkaline protease-hydrolyzed SPI at selected DH (1%-6%).The influence of bromelain, pepsin, and trypsin proteases on the structure of SPI-gum Arabic complexes demonstrated that the complex of pepsintreated SPI (especially protein treated for 3 h) and gum Arabic exhibited a stable emulsion with high solubility, uniform PSD, absolute charge value, and antioxidant properties (Zhao, Zheng, et al., 2022).
An improvement of the oxidative and physical stabilities of FBPI hydrolysate-stabilized O/W emulsions by moderate alcalase hydrolysis (DH of 4%) was reported by Liu, Bhattarai, et al. (2019).However, the main constraint of this method is the development of bitter aftertaste, which is produced by low-molecular-weight peptides of hydrophobic amino acids and limits the application of legume-based hydrolysates as an ingredient in food products (Nasrabadi et al., 2021).
Therefore, proteins with higher lysine and glutamine contents are potentially more favorable substrates for the TGase enzyme.These cross-linking reactions promote the chemical bonding of adjacent protein molecules and form a new tertiary network structure, which can improve the water-binding capacity, stability, and mechanical properties of the proteins (Huang, Sun, Zhao, He, Liu, & Liu, 2022).Glusac et al. (2020) evaluated the effects of TGase on the digestibility and physical stability of chickpea protein isolate (CPI)-stabilized o/w emulsions.Cross-linking improved the gel-forming ability and physical stability of emulsions for more than a month.The in vitro digestibility TGase-SPI-stabilized emulsions decreased, which is favorable for producing emerging plant-based foods with controlled energy intake.A higher emulsion stability and lower surface hydrophobicity (504-435 RFU) were observed for TGase-treated FBPI-stabilized emulsions (Nivala et al., 2021).The authors reported an improvement in the rheological properties and higher water-holding capacity (>98%) for TGase-induced gels.For TGase-treated SPI, 7S, and 11S, sulfhydryl and surface hydrophobicity were lower; conversely, both the DH and the β-sheets contents were increased significantly (Huang, Sun, Zhao, He, Liu, & Liu, 2022).Luo et al. (2019) observed more resistance to deformation of the gels when SPI emulsions were treated with low TGase concentrations (1 and 3 U/g protein) prior to the gelation.TGase treatments reduced the number of non-covalent bonds within the gel network, which may limit hydrophobic interactions and reduce gel firmness, particularly when extensive crosslinking was used (TGase concentration of 5 U/g protein).

| COMBINED MODIFICATIONS
In order to overcome the limitations of the native proteins and improve the functional and interfacial properties of the singlemodified proteins, combined (dual or multiple) modifications have received a great deal of attention (Table 3).pH adjustment is frequently used in conjunction with HP treatment (Tan et al., 2021), CPP treatment (Zhang, Huang, et al., 2022), sonication treatment (Jiang et al., 2022;Liu, Hu, Du, Liao, et al., 2022;Zhang, Liu, et al., 2022), and heating treatment (Zhi et al., 2022).The results obtained from these studies suggest that these treatments exhibit synergistic effects and T A B L E 3 Combined modifications of legume protein-based colloidal systems HP treatment (300, 450, and (Zhi et al., 2022) significantly improve the emulsifying and interfacial properties of single or mixed legume protein-based colloidal systems.For instance, higher solubility, surface charge, unfolding, emulsion stability, gel strength, and viscosity of SPI and PPC were achieved by using pH adjustment-HP and pH adjustment-CPP modifications (Tan et al., 2021;Zhang, Huang, et al., 2022).Similarly, the application of combined pH adjustment and sonication significantly improved the emulsion ability and stability, physical and oxidative stability, solubility, and viscosity of stabilized emulsions with different types of legume proteins.Overall, β-sheet and random coil contents, surface hydrophobicity, free SH groups, and fluorescence intensity were increased, whereas α-helix and β-turn contents and the mean particle size (Dv50) lowered (Figure 2) (Liu, Hu, Du, Liao, et al., 2022;Zhang, Liu, et al., 2022).These effects were more pronounced by using complex emulsifiers (Jiang et al., 2022) or trinary (pH adjustment, sonication, and heating) modifications (Zhi et al., 2022).
A combined treatment of HP treatment (300, 450, and 600 MPa/15 min) and enzymatic hydrolysis (alcalase, 0.5% and 1%, w/w) improved the %DH of the LPI (Ahmed et al., 2019).The produced hydrolysates improved the foaming properties (≈1.5 times) and antioxidant activities (≈2 times) compared to the untreated LPI.However, a detrimental effect was pronounced on the emulsifying activity and stability index, foam stability, and water-holding capacity of the hydrolysates.In another study, effects of combining HPH treatment with heating and sonication treatments on the functional properties of SPI gels and PPI-XOS conjugates were assessed (Huang, Wang, Zhang, Liu, Zhou, Chi, Gao, et al., 2022;Zhao, Huang, et al., 2022).
The shear-thickening behavior and gelling ability of SPI gels were improved by combining HPH and heating treatment.On the other hand, HPH-sonication treatment enhanced the Maillard reaction between the PPI and the XOS and improved the functionality of PPI-XOS conjugates, as illustrated in Figure 3 and Table 3.  Li and Chen (2022) studied the physicochemical properties of a heat-treated SPI-epigallocatechin-3-gallate (EGCG) complex using an alkali covalent cross-linking technique as a nanocarrier for curcumin.
The heat-treated complex showed a better loading rate of curcumin, bioaccessibility, thermal and acid stability, scavenging capacity, and binding affinity.A combined treatment of heating and enzymatic cross-linking increased the surface hydrophobicity, emulsion stability, and water-holding capacity of FBPI gels (Nivala et al., 2021).Qu et al. properties and freeze-thaw stability (Figure 3 and Table 3) (Wang, Jiao, et al., 2022).These findings show that the combined modifications significantly improve the functional and interfacial properties of legume protein-based colloidal systems, with potential applications in the food and pharmaceutical industries as a promising delivery polymer carrier of bioactive components.

| CONCLUSION
In the past few years, intensive research has been conducted on the modification of legume-based proteins to improve their technofunctional and interfacial properties in different colloidal systems.
Generally, physical, chemical, enzymatic, and combined (dual or multiple) treatment can modify the functionality of legume proteins in various ways.The mechanism of protein modifications lies on the disrupting and breaking the intermolecular hydrogen and hydrophobic interactions, partially unfolding the structure, exposing the buried hydrophobic and sulfhydryl groups, and forming more flexible conformation so that it can be used as a designer's protein to fabricate products with desired properties.A careful selection of each of these methods or their combinations could bring a favorable interfacial functionality, which can be successfully applied in functional and engineered colloids in the food and pharmaceutical formulations as a sustainable technique for the production of emerging colloidal systems.
HP treatment is one of the most successful nonthermal techniques applied to food in the pressure range of 300 MPa to 600 MPa for a F I G U R E 1 Different mechanisms of ultrasound treatment for modification of protein-based colloidal systems (Su & Cavaco-Paulo, 2021) T A B L E 1 Effects of sonication on the functional and interfacial properties of legume protein-based colloidal systems

("
et al.(2021)  reported that HPH can influence the structural and emulsifying properties of the kidney bean protein isolate (KBPI) in two ways: (1) by forming disulfide bonds between molecules and increasing particle size at low pressures (30 to 60 MPa) and (2) by breaking disulfide bonds and damaging protein aggregates at high pressures (90 to 120 MPa).Saricaoglu (2020) investigated the ability of HPH (25 to 150 MPa) to modify the functional, structural, and rheological properties of lentil protein isolate (LPI) suspensions (4% protein concentration; 4.76 g LPI/100 ml of water).The emulsifying activity index (EAI) of LPI suspensions was not significantly affected by the HPH treatment up to 25 MPa; however, LPI suspensions showed the highest EAI values when pressure ranged between 50 and 100 MPa.A further increase in pressure to 150 MPa caused a significant decrease in EAI.Similar behavior was reported for the emulsion stability index (ESI) of HPH-treated LPI suspensions.The increased emulsifying properties of LPI suspensions with HPH could be attributed to the partial dissociation and unfolding of protein structure, which results in a higher hydrophobic and hydrophilic interaction of proteins.Tabilo-Munizaga et al. (2019) reported the formation of lentil protein-based stable nanoemulsions using HPH (50-300 MPa) in a selected number of passes (1-3) and emulsifier to oil ratios (1:1, 1:2, and 2:1).The particle size distribution (PSD) of 1:1 lentil nanoemulsion changed from multimodal to bimodal at a pressure higher than 100 MPa, regardless of homogenization passes.Two homogenization passes and ratios of 1:1 and 2:1 improved the reduction of droplet size (587-149 nm) and polidispersity index (PdI) (0.821-0.168), with T A B L E 2 (Continued) 15 min " Gelling ability, elastic modulus (G 0 ), hardness, and water-holding capacity (Zhao et al., 2020) PPI 50, 70, 80, 90, and 100 C for 15 min, at pH 3, 5, and 7 " Emulsion-forming ability and oil droplet size (at pH 5) # Oil droplet size (at pH 7) and foaming ability -Higher aggregation at 80-100 C -The highest denaturation level at pH 3 Surface charge, carbonyl groups and disulfide bonds contents, oxidation efficiency, and ordered secondary structure # Interfacial tension (Mehr & Koocheki, 2020) Voltage of 9.4 and 18.6 kV, frequency of 20 kHz, and duration of 300 and 600 s " Surface hydrophobicity # Particle size, ordered structure, ζpotential, free SH groups, and solubility $ Cytotoxicity content in human cells (Mehr & Koocheki, 2021) PPC Voltage of 0-30 kV, frequency of 3,500 Hz, and duration of 10 min " Surface hydrophobicity and gel strength # Fluorescence intensity, ζ-potential, free SH groups, and solubility $ NH 2 content

( 2023 )
examined the possible application of a cold plasma synergistic tartaric acid treatment to induce the deamidation of PPI-based foam stabilizers.It was observed that the CPP treatment prolonged the PPI deamidation (20.02%) by improving protein foamability, foam stability, and surface hydrophobicity.A combination of TGase and ionic (CaCl 2 ) cross-linking treatments on PPI-sodium alginate (SA) double-network hydrogels resulted in an improvement in rheological and textural 600 MPa/15 min) and enzymatic hydrolysis [alcalase (0.5% and 1%, w/w)]