Thermosonication-induced structural changes and solution properties of mung bean protein

Mung bean protein isolate: Extraction, structure, physicochemical properties, modifications, and food applications

The intake of plant-based proteins is rapidly growing around the world due to their nutritional and functional properties, as well as growing demand for vegetarian and vegan diets. Mung bean seeds have been traditionally consumed in Asian countries due to their unique botanical and health-promoting characteristics. In recent years, mung bean protein isolate (MBPI) has attracted much attention due to its ideal techno-functional features, such as water and oil absorption capacity, solubility, emulsifying, foaming, and thermal properties. Therefore, it can be utilized in a native or modified form in different food sectors, such as biodegradable/edible films, colloidal systems, and plant-based alternative products. This study provides a comprehensive review on the extraction methods, amino acid profile, structure, physicochemical properties, modifications, and food applications of MBPI.

Ultrasonic-Assisted Extraction of Dictyophora rubrovolvata Volva Proteins: Process Optimization, Structural Characterization, Intermolecular Forces, and Functional Properties

Dictyophora rubrovolvata volva, an agricultural by-product, is often directly discarded resulting in environmental pollution and waste of the proteins' resources. In this study, D. rubrovolvata volva proteins (DRVPs) were recovered using the ultrasound-assisted extraction (UAE) method. Based on one-way tests, orthogonal tests were conducted to identify the effects of the material-liquid ratio, pH, extraction time, and ultrasonic power on the extraction rate of DRVPs. Moreover, the impact of UAE on the physicochemical properties, structure characteristics, intermolecular forces, and functional attributes of DRVPs were also examined. The maximum protein extraction rate was achieved at 43.34% under the best extraction conditions of UAE (1:20 g/mL, pH 11, 25 min, and 550 W). UAE significantly altered proteins' morphology and molecular size compared to the conventional alkaline method. Furthermore, while UAE did not affect the primary structure, it dramatically changed the secondary and tertiary structure of DRVPs. Approximately 13.42% of the compact secondary structures (α-helices and β-sheets) underwent a transition to looser structures (β-turns and random coils), resulting in the exposure of hydrophobic groups previously concealed within the molecule's core. In addition, the driving forces maintaining and stabilizing the sonicated protein aggregates mainly involved hydrophobic forces, disulfide bonding, and hydrogen bonding interactions. Under specific pH and temperature conditions, the water holding capacity, oil holding capacity, foaming capacity and stability, emulsion activity, and stability of UAE increased significantly from 2.01 g/g to 2.52 g/g, 3.90 g/g to 5.53 g/g, 92.56% to 111.90%, 58.97% to 89.36%, 13.85% to 15.37%, and 100.22% to 136.53%, respectively, compared to conventional alkali extraction. The findings contributed to a new approach for the high-value utilization of agricultural waste from D. rubrovolvata.

Enhancing the stability of mung bean-based milk: Insights from protein characteristics and raw material selection

Plant-based milk (PBM) alternatives are gaining popularity worldwide as the change of consumers' nutritional habits and health attitudes. Mung beans, recognized for their nutritional value, have gained attention as potential ingredients for PBM. Nevertheless, mung bean-based milk (MBM) faces instability issues common to other plant-based milks. This study investigated the factors influencing MBM stability focusing on raw materials. We selected 6 out of 20 varieties based on their MBM centrifugation sedimentation rates, representing both stable and unstable MBM. Stable MBM exhibited distinct advantages, including reduced separation rate, smaller particle size, lower viscosity, fewer protein aggregates, higher soluble protein content, and increased consumer acceptance. Major nutritional components such as protein, starch, and lipids were not significant different between stable and unstable MBM varieties. The pivotal distinction may lay in the protein properties and composition. Stable MBM varieties exhibited significantly improved protein solubility and emulsion stability, along with elevated concentrations of legume-like acidic subunits, basic 7S proteins, and 28 kDa and 26 kDa vicilin-like subunits. The increasement of these proteins likely contributed to the improvement in protein characteristics that affect MBM stability. These findings offer valuable insights for raw material selection and guidance for future mung bean breeding to enhance mung bean milk production.

Mung bean protein as an emerging source of plant protein: a review on production methods, functional properties, modifications and its potential applications

Plant protein is rapidly becoming more of a prime interest to consumers for its nutritional and functional properties, as well as the potential to replace animal protein. In the frame of alternative protein new sources, mung bean is becoming another legume crop that could provide high quality plant protein after soybean and pea. In particular, the 8S globulins in mung bean protein have high structural similarity and homology with soybean β-conglycinin (7S globulin), with 68% sequence identity. Currently, mung bean protein has gained popularity in food industry because of its high nutritional value and peculiar functional properties. In that regard, various modification technologies have been applied to further broaden its application. Here, we provide a review of the composition, nutritional value, production methods, functional properties and modification technologies of mung bean protein. Furthermore, its potential applications in the new plant-based products, meat products, noodles, edible packaging films and bioactive compound carriers are highlighted to facilitate its utilization as an alternative plant protein, thus meeting consumer demands for high quality plant protein resources. © 2023 Society of Chemical Industry.

Effects of nitrogen fertilizer on the physicochemical, structural, functional, thermal, and rheological properties of mung bean (Vigna radiata) protein

Nitrogen fertilizer can affect the seed quality of mung bean. However, the effects of nitrogen fertilizer on the properties of mung bean protein (MBP) remain unclear. We investigated the effects of four nitrogen fertilization levels on the physicochemical, structural, functional, thermal, and rheological properties of MBP. The results showed that the amino acid and protein contents of mung bean flour were maximized under 90 kg ha-1 of applied nitrogen treatment. Nitrogen fertilization can alter the secondary and tertiary structure of MBP. The main manifestations are an increase in the proportion of β-sheet, the exposure of more chromophores and hydrophobic groups, and the formation of loose porous aggregates. These changes improved the solubility, oil absorption capacity, emulsion activity, and foaming stability of MBP. Meanwhile, Thermodynamic and rheological analyses showed that the thermal stability, apparent viscosity, and gel elasticity of MBP were all increased under nitrogen fertilizer treatment. Correlation analysis showed that protein properties are closely related to changes in structure. In conclusion, nitrogen fertilization can improve the protein properties of MBP by modulating the structure of protein molecules. This study provides a theoretical basis for the optimization of mung bean cultivation and the further development of high-quality mung bean protein foods.

Physical Stability of Lotus Seed and Lily Bulb Beverage: The Effects of Homogenisation on Particle Size Distribution, Microstructure, Rheological Behaviour, and Sensory Properties

The lotus seed and lily bulb beverage (LLB) has a problem with solid particle sedimentation. To address this issue, LLB was homogenised twice at different pressures (0~100 MPa) using a homogeniser. This study aims to investigate the changes in the particle size distribution (PSD), microstructure, rheological behaviour, sedimentation index (IS), turbidity, physicochemical properties, and sensory quality of LLBs after homogenisation treatments. The results regarding PSD and microstructure showed that the suspended particles were decomposed at high pressure with increasing homogenisation pressure, forming small particles of cellular material, cell wall fragments, fibre fractions, and polymers. The LLB showed shear-thinning behaviour and weak gelation characteristics (G' > G″) and rheological properties. Among all homogenisation pressures, the 60 MPa sample showed the lowest sedimentation rate and the highest turbidity. When the pressure was increased from 0 to 100 MPa, the total soluble solid (TSS) content showed an upward trend, while the ascorbic acid content (AAC) gradually decreased. The highest sensory evaluation was observed in the 60 MPa sample in terms of overall acceptability.

Hexagonal plate ultrasound pretreatment on the correlation between soy protein isolate structure and cholesterol-lowering activity of peptides, and protein's enzymolysis kinetics, thermodynamics

In this study, a hexagonal plate ultrasound (HPU) pretreatment technology was employed to modify soy protein isolate (SPI) and enhance the hypocholesterolemic activity of enzymatic digests from SPI. Results demonstrated that under the condition of ultrasound power density of 40 W/L, the hypocholesterolemic activity of enzymatic digests from HPU-pretreated SPI (HPU-SPI) increased by 88.40 % compared to control group after gastrointestinal digestion. The sulfhydryl content of HPU-SPI increased by a maximum of 45.32 % compared to control group. Fourier transform infrared and scanning electron microscopy revealed that HPU pretreatment partially unfolded the SPI conformation, reduced the intermolecular interactions, and exposed the internal hydrophobic regions. Pearson correlation analysis showed that sulfhydryl groups (r = 0.860), disulfide bonds (r = -0.875) and random coil (r = 0.917) were strongly correlated with the cholesterol-lowering activity of soy protein hydrolysate (SPH), following a simulated gastrointestinal digestion. Finally, the effects of HPU pretreatment on enzymolysis kinetics and thermodynamics of the SPI enzymatic process showed that HPU pretreatment significantly reduced the Mie's constant, activation energy, activation enthalpy, activation entropy and Gibbs free energy. Overall, the study outcome suggested that HPU pretreatment could positively influence the hypocholesterolemic peptide activity, and thus, may be beneficial to the pharmaceutical/food industry.

Structural modification of oat protein by thermosonication combined with high pressure for O/W emulsion and model salad dressing production

Oat protein is becoming an important ingredient in beverages and formulated foods owing to its high nutritive value and bland flavor; yet, its functionality remains largely unexplored. This study sought to enhance the surface activity of oat protein isolate (OPI) through high-intensity ultrasound (HIU; at 20 or 60 °C) combined with high pressure homogenization (HP; 30 MPa) treatments. Sonication disturbed the protein conformation and significantly improved surface hydrophobicity (19.7%) and ζ-potential (15.7%), which were further augmented by subsequent HP (P < 0.05). Confocal microscopy revealed a uniform oil droplet distribution in emulsions prepared with HIU+HP combination treated OPI, and the oil droplet size decreased up to 35.6% when compared to that of non-treated OPI emulsion (d = 1718 nm). Emulsifying activity was greater for HIU+HP than for HIU, and the viscosity followed a similar trend. Moreover, while emulsions prepared with HIU or HP treated OPI were more stable than control, the 60 °C HIU+HP combination treatment yielded the maximum stability. In corroboration, a model salad dressing prepared from HIU+HP treated OPI displayed a homogenous oil droplet distribution and an improved viscosity. Therefore, thermosonication combined with high pressure homogenization may be suitable for salad dressings and other oil-imbedded food products.

Effect of ultrasonic assisted grafting on the structural and functional properties of mung bean protein isolate conjugated with maltodextrin through maillard reaction

Four different methods of maillard reaction including ultrasound (150 W, 10 min) assisted, classical wet heating (80 °C, 60min), moderate water bath heating (60°C, 12 to 30 h) and dry state method (60 °C, 79 % relative humidity and 48 h) were used to Mung bean protein isolate - Maltodexrtin conjugates (MPI-MD) preparation. The samples prepared under ultrasound and wet heating were chosen for further analysis according to degree of graft and UV-absorbance at 420 nm. Higher glycosylation at short time and lower browning were obtained under ultrasound treatment. Covalent attachment in conjugates confirmed by SDS-polyacrylamide gel electrophoresis. The structural analysis revealed prominent unfolding effect of ultrasound waves on the protein's molecules. The decrease of α-helix content was related to the exposure of buried amino group residues during reaction. Glycation of MPI under ultrasound caused changes in tertiary structure of protein and leads to decrease in the fluorescence intensity compared with native and wet heating treatments. FTIR spectra confirmed the conjugation of the MPI and MD and suggested that protein structure was changed and ultrasound promoted the graft reaction more than wet heating treatment. Conjugated MPI showed higher emulsification and solubility index than MPI, moreover the effect of ultrasonic waves on ameliorated functional properties was impressive than those for wet heating treatment. Overall, this study showed use of ultrasonication in maillard reaction was a suitable method for producing MPI- MD conjugates and improved the efficiency of graft reaction and functional properties of grafts.

Comparison between hydrodynamic and ultrasound cavitation on the inactivation of lipoxygenase and physicochemical properties of soy milk

The effects of hydrodynamic cavitation (HC) and ultrasound cavitation (UC) on the lipoxygenase activity and physicochemical properties of soy milk were evaluated. The results revealed that both ultrasound cavitation and hydrodynamic cavitation significantly inactivated the lipoxygenase activity. After the exposure to ultrasound cavitation at 522.5 W/L and 70 °C for 12 min, the lipoxygenase activity was inactivated by 96.47 %. Meanwhile, HC treatment with the cavitation number of 0.0133 for 240 min led to the loss of 79.31 % of lipoxygenase activity. An artificial neural network was used to model and visualize the effects of different parameters after ultrasound cavitation treatment on the inactivation efficiency of soy milk. Turbiscan test results showed that hydrodynamic and ultrasound cavitation decreased the instability index and particle size of soy milk. Moreover, the total free amino acid content was significantly increased after hydrodynamic and ultrasound cavitation treatment. Gas chromatography-mass spectrometry showed that the total content of beany flavor compounds decreased after acoustic cavitation and HC treatment. Acoustic cavitation and HC affected the tertiary and secondary structure of soy milk, which was related to the inactivation of lipoxygenase. We aim to explore a potential and effective way of the application in soy milk processing by comparing the ultrasound equipped with heat treatment and hydrodymic cavitation.

Effects of sound energy on proteins and their complexes

Mechanical energy in the form of ultrasound and protein complexes intuitively have been considered as two distinct unrelated topics. However, in the past few years, increasingly more attention has been paid to the ability of ultrasound to induce chemical modifications on protein molecules that further change protein-protein interaction and protein self-assembling behavior. Despite efforts to decipher the exact structure and the behavior-modifying effects of ultrasound on proteins, our current understanding of these aspects remains limited. The limitation arises from the complexity of both phenomena. Ultrasound produces multiple chemical, mechanical, and thermal effects in aqueous media. Proteins are dynamic molecules with diverse complexation mechanisms. This review provides an exhaustive analysis of the progress made in better understanding the role of ultrasound in protein complexation. It describes in detail how ultrasound affects an aqueous environment and the impact of each effect separately and when combined with the protein structure and fold, the protein-protein interaction, and finally the protein self-assembly. It specifically focuses on modifying role of ultrasound in amyloid self-assembly, where the latter is associated with multiple neurodegenerative disorders.

Effect of Na+ and Ca2+ on the texture, structure and microstructure of composite protein gel of mung bean protein and wheat gluten

To investigate the change of ionic strength on the gel characteristics during the processing of mung bean protein-based foods, the effects of NaCl and CaCl2 at different concentrations (0-0.005 g/mL) on the properties of mung bean protein (MBP) and wheat gluten (WG) composite protein gel were studied. The results showed that low concentration (0.001-0.002 g/mL) could significantly improve the water holding capacity (WHC), storage modulus (G') and texture properties of composite protein gel (MBP/WG), while the surface hydrophobicity (H0) and solubility were significantly decreased (P < 0.05). With the increase of ion concentration, the secondary structures of MBP/WG shifted from α-helix to β-sheet, and the fluorescence spectra also showed fluorescence quenching phenomenon. By analyzing the intermolecular forces of MBP/WG, it was found that with the addition of salt ions, the hydrogen bonds was weakened and the electrostatic interactions, hydrophobic interactions and disulfide bonds were enhanced, which in turn the aggregation behavior of MBP/WG composite protein gel was affected and larger aggregates between the proteins were formed. It could be also demonstrated that the gel network was denser due to the addition of these large aggregates, thus the gel properties of MBP/WG was improved. However, too many salt ions could disrupt the stable network structure of protein gel. This study can provide theoretical support to expand the development of new mung bean protein products.

Modification of the Structural and Functional Characteristics of Mung Bean Globin Polyphenol Complexes: Exploration under Heat Treatment Conditions

During the storage and processing of mung beans, proteins and polyphenols are highly susceptible to interactions with each other. Using globulin extracted from mung beans as the raw material, the study combined it with ferulic acid (FA; phenolic acid) and vitexin (flavonoid). Physical and chemical indicators were combined with spectroscopy and kinetic methods, relying on SPSS and peak fit data to statistically analyze the conformational and antioxidant activity changes of mung bean globulin and two polyphenol complexes before and after heat treatment and clarify the differences and the interaction mechanism between globulin and the two polyphenols. The results showed that, with the increase in polyphenol concentration, the antioxidant activity of the two compounds increased significantly. In addition, the antioxidant activity of the mung bean globulin-FA complex was stronger. However, after heat treatment, the antioxidant activity of the two compounds decreased significantly. The interaction mechanism of the mung bean globulin-FA/vitexin complex was static quenching, and heat treatment accelerated the occurrence of the quenching phenomenon. Mung bean globulin and two polyphenols were combined through a hydrophobic interaction. However, after heat treatment, the binding mode with vitexin changed to an electrostatic interaction. The infrared characteristic absorption peaks of the two compounds shifted to different degrees, and new peaks appeared in the areas of 827 cm^-1, 1332 cm^-1, and 812 cm^-1. Following the interaction between mung bean globulin and FA/vitexin, the particle size decreased, the absolute value of zeta potential increased, and the surface hydrophobicity decreased. After heat treatment, the particle size and zeta potential of the two composites decreased significantly, and the surface hydrophobicity and stability increased significantly. The antioxidation and thermal stability of the mung bean globulin-FA were better than those of the mung bean globulin-vitexin complex. This study aimed to provide a theoretical reference for the protein-polyphenol interaction mechanism and a theoretical basis for the research and development of mung bean functional foods.

A mini-review about direct steam heating and its application in dairy and plant protein processing

The world's requirement for plant protein consumption is increasing. However, their application in different foods is limited due to their low techno-functionality. Heating is the most widely used method to improve the functionality of proteins. Compared to indirect tubular or plate heating methods, direct steam injection heating (DSIH) can heat the sample much faster, thus modifying the structure and functionality of protein differently. It is used in the sterilization of milk to minimize the heat-induced denaturation of whey proteins and the loss of volatiles. By contrast, its application in producing plant protein ingredients is seldom. This review summarizes recent research using DSIH to process dairy- and plant-based proteins and proposes future research perspectives. DSIH is a promising technique for producing functional protein ingredients. It is of particular interest to overcome the techno-functional hurdles of plant protein blends using DSIH to improve their behavior in different food matrices.

Possible role of polypeptide-chlorogenic acid interaction in the physicochemical and sensory characteristics of quinoa-modified coffee beverage

The effect of quinoa protein hydrolysate (QPH) beverage on the physicochemical and sensory characteristics of coffee was investigated. The scores of sensory properties of coffee-quinoa beverage revealed that the unpleasant sensory characteristics, such as extreme bitterness and astringency, were covered up by the addition of quinoa beverage; while smooth mouthfeel and sweetness were enhanced. On the other hand, the introduction of coffee into quinoa beverage significantly retarded oxidation characterized by TBARS. When treated with chlorogenic acid (CGA), significant structural changes and improved functionalities of QPH were detected. CGA induced the unfolding structure of QPH and decreased surface hydrophobicity. The interaction between QPH and CGA was shown by the changes of sulfydryl content and the pattern of SDS-PAGE. Besides, neutral protease treatment increased the equilibrium oil-water interfacial pressure value of QPH, revealing improved stability of emulsions. Synergistic antioxidant effect between QPH and CGA was revealed by increased ABTS^+· scavenging rate.

Effects of dual succinylation and ultrasonication modification on the structural and functional properties of ovalbumin

In this study, the functional properties of ovalbumin (OVA) were improved through dual modification with succinylation (succinylation degrees of 32.1 % [S1], 74.2 % [S2], and 95.2 % [S3]) and ultrasonication (ultrasonication durations of 5 min [U1], 15 min [U2], and 25 min [U3]), and the changes in protein structures were explored. Results showed that as the succinylation degree was increased, the particle size and surface hydrophobicity of S-OVA decreased by the maximum values of 2.2 and 2.4 times, respectively, causing emulsibility and emulsifying stability to increase by 2.7 and 7.3 times, respectively. After ultrasonic treatment, the particle size of succinylated-ultrasonicated OVA (SU-OVA) had decreased by 3.0-5.1 times relative to that of S-OVA. Moreover, the net negative charge of S3U3-OVA had increased to the maximum value of - 35.6 mV. These changes contributed to the further enhancement in functional indicators. The unfolding of the protein structure and the conformational flexibility of SU-OVA were illustrated and compared with those of S-OVA via protein electrophoresis, circular dichroism spectroscopy, intrinsic fluorescence spectroscopy, and scanning electron microscopy. The dually modified OVA emulsion (S3U3-E) presented small droplets (243.33 nm), reduced viscosity, and weakened gelation behavior that were indicative of even distribution, which was visually proven by confocal laser scanning microscopy images. Furthermore, S3U3-E exhibited favorable stability, a particle size that was almost unchanged, and a low polydispersity index (<0.1) over 21 days of storage at 4 °C. The above results demonstrated that succinylation combined with ultrasonic treatment could be an effective dual modification method for enhancing the functional performance of OVA.

Effect of maltodextrin on the oxidative stability of ultrasonically induced soybean oil bodies microcapsules

Introduction

Encapsulation of soybean oil bodies (OBs) using maltodextrin (MD) can improve their stability in different environmental stresses and enhance the transport and storage performance of OBs.

Methods

In this study, the effects of different MD addition ratios [OBs: MD = 1:0, 1:0.5, 1:1, 1:1.5, and 1:2 (v/v)] on the physicochemical properties and oxidative stability of freeze-dried soybean OBs microcapsules were investigated. The effect of ultrasonic power (150–250 W) on the encapsulation effect and structural properties of oil body-maltodextrin (OB-MD) microcapsules were studied.

Results

The addition of MD to OBs decreased the surface oil content and improved the encapsulation efficiency and oxidative stability of OBs. Scanning electron microscopy images revealed that the sonication promoted the adsorption of MD on the surface of OBs, forming a rugged spherical structure. The oil-body-maltodextrin (OB-MD) microcapsules showed a narrower particle size distribution and a lower-potential absolute value at an MD addition ratio of 1:1.5 and ultrasonic power of 250 W (32.1 mV). At this time, MD-encapsulated OBs particles had the highest encapsulation efficiency of 85.3%. Ultrasonic treatment improved encapsulation efficiency of OBs and increased wettability and emulsifying properties of MD. The encapsulation of OBs by MD was improved, and its oxidative stability was enhanced by ultrasound treatment, showing a lower hydrogen peroxide value (3.35 meq peroxide/kg) and thiobarbituric acid value (1.65 μmol/kg).

Discussion

This study showed that the encapsulation of soybean OBs by MD improved the stability of OBs microcapsules and decreased the degree of lipid oxidation during storage. Ultrasonic pretreatment further improved the encapsulation efficiency of MD on soybean OBs, and significantly enhanced its physicochemical properties and oxidative stability.

Effect of Ionic Strength on Heat-Induced Gelation Behavior of Soy Protein Isolates with Ultrasound Treatment

This study investigated the effect of ultrasound on gel properties of soy protein isolates (SPIs) at different salt concentrations. The results showed that ultrasound could significantly improve the gel hardness and the water holding capacity (WHC) of the salt-containing gel (p < 0.05). The gel presents a uniform and compact three-dimensional network structure. The combination of 200 mM NaCl with 20 min of ultrasound could significantly increase the gel hardness (four times) and the WHC (p < 0.05) compared with the SPI gel without treatment. With the increase in NaCl concentration, the ζ potential and surface hydrophobicity increased, and the solubility decreased. Ultrasound could improve the protein solubility, compensate for the loss of solubility caused by the addition of NaCl, and further increase the surface hydrophobicity. Ultrasound combined with NaCl allowed proteins to form aggregates of different sizes. In addition, the combined treatment increased the hydrophobic interactions and disulfide bond interactions in the gel. Overall, ultrasound could improve the thermal gel properties of SPI gels with salt addition.

Relationship between flexibility and interfacial functional properties of soy protein isolate: succinylation modification

BACKGROUND

In this paper, the effects of different succinic anhydride (SA) additions on the flexibility of soy protein isolate (SPI) were investigated, and changes in protein conformation and interfacial functional properties were measured. The structure-effect relationship between conformation, flexibility, and interfacial functional properties was established.

RESULTS

SPI was bound to SA through disulfide bonds, and the zeta potential was reduced. The β-sheet content decreased, the disordered structure increased, and there were changes in tertiary structure and microstructure. The surface hydrophobicity, disulfide bond content, and solution turbidity were reduced to 5063, 1.0967 μmol g-1 , and 0.0036 μmol g-1 respectively. The best flexibility of SPI (0.3977) and interfacial functional properties were obtained when the mass ratio of SA/SPI was 15%. Correlation analysis showed a highly significant positive correlation (P < 0.01) between flexibility and emulsification and foaming properties, with correlation coefficients of 0.960 and 0.942 for flexibility with emulsifying activity and emulsion stability respectively, and 0.972 and 0.929 for flexibility with foaming capacity and foaming stability respectively.

CONCLUSION

The results suggest that succinylation-induced conformational changes of SPI improved its interfacial functional properties by changing its flexibility. These results provide theoretical guidelines for the development and application of highly emulsifiable and stable soy protein products utilizing succinylation. © 2022 Society of Chemical Industry.

Recent advances on the impact of novel non-thermal technologies on structure and functionality of plant proteins: A comprehensive review

The recent trend in consumption of plant-based protein over animal protein opens up a new avenue for sustainable agriculture practice, less environmental impact and greenhouse gas emission. The modification of plant-based proteins by novel non-thermal technologies includes the structural transformation followed by the modulation of their functional properties that are exploited to develop a protein ingredient system for application in food formulation. This review explores the impact of non-thermal process technologies on structural modification of plant proteins followed by improvement in protein's function in food formulation. Novel concepts articulating the impact of non-thermal technologies on structural and functional modification of plant proteins affecting it's digestibility and bioavailability are addressed. Limitations and prospects of applying non-thermal technologies in developing an alternative plant-based protein food system are also summarized. Non-thermal processes are considered as the emerging technologies that results in conformational changes in secondary, tertiary and quaternary structure of plant proteins which helps in modification of functional properties without jeopardizing the organoleptic properties and bioactivity of the protein. However, extensive future study is needed to optimize the non-thermal process parameters along with the finding of new protein sources to achieve healthy and sustainable plant-based food system.

Curcumin-loaded complex coacervate made of mung bean protein isolate and succinylated chitosan as a novel medium for curcumin encapsulation

A novel complex coacervate based on mung bean protein (MBP) and succinylated chitosan (SC) was developed in order to encapsulate curcumin to enhance its antioxidant and release properties. The optimum pH and MBP/SC ratio for fabrication of the complex coacervate were determined as 5.5 and 3:1, respectively. The MBP/SC complexes exhibited high affinity toward curcumin with encapsulation efficiency of 89.65%. The curcumin-loaded MBP with succinyl chitosan (c-MBP/SC) exhibited antioxidant properties investigated by DPPH and reducing power assays. c-MBP/SC also showed significant photo stability and acceptable controlled release behavior in simulated gastrointestinal conditions. Fluorescence results indicated that curcumin interacted with the hydrophobic areas available in c-MBP/SC. FTIR results showed the successful encapsulation of curcumin in the hydrophobic core of the complex, followed by minor changes in MBP conformation. Analysis of zeta potential revealed that MBP/SC particles were synthesized successfully at the pH value of 5.5 due to conformational changes of MBP. The conformational changes in protein structure were confirmed by Nile Red fluorescence anisotropy. As a result, c-MBP/SC could be considered as a promising carrier for curcumin encapsulation in food formulations with enhanced dispersity characteristic.

Effects of ultrasonic treatment on ovomucin: Structure, functional properties and bioactivity

The effects of ultrasonic treatment on the structure, functional properties and bioactivity of Ovomucin (OVM) were investigated in this study. Ultrasonic treatment could significantly enhance OVM solubility without destroying protein molecules. The secondary structure changes, including β-sheet reduction and random coil increase, indicate more disorder in OVM structure. After ultrasonic treatment, the OVM molecule was unfolded partially, resulting in the exposure of hydrophobic regions. The changes in OVM molecules led to an increase in intrinsic fluorescence and surface hydrophobicity. By detecting the particle size of protein solution, it was confirmed that ultrasonic treatment disassembled the OVM aggregations causing a smaller particle size. Field emission scanning electron microscopy (FE-SEM) images showed that ultrasonic cavitation significantly reduced the tendency of OVM to form stacked lamellar structure. Those changes in structure resulted in the improvement of foaming, emulsification and antioxidant capacity of OVM. Meanwhile, the detection results of ELISA showed that ultrasonic treatment did not change the biological activity of OVM. These results suggested that the relatively gentle ultrasound treatment could be utilized as a potential approach to modify OVM for property improvement.

Hydrothermal-induced changes in the gel properties of Mung bean proteins and their effect on the cooking quality of developed compound noodles

Mung bean proteins (MBPs) are highly nutritious food ingredients, but their lack of gluten limits their use in staple foods such as noodles. In this study, MBPs were modified by hydrothermal treatment, and their gel properties and the major structural changes were analyzed at different heating temperatures (25, 65, 75, 85, 95, and 105°C), moisture contents (0, 15, 20, 25, 30, and 35%), and hydrothermal treatment times (0, 15, 30, 45, 60, and 75 min). Thereafter, the modified MBPs (MMBPs) were added to wheat noodles at substitution levels of 3, 6, and 9% to evaluate their effect on the quality of the noodles. The results showed that the hydrothermal treatment significantly improved the gel properties and water absorption capacity of the MBPs and slightly increased their disulfide bond content. When MBPs with a 25% moisture content were heated at 85°C for 60 min, their gel properties notably improved, and their structural changes were maximal. The structural changes revealed that the MBP molecule formed a macromolecular polymer because a significant protein band appeared at about 66.2 kDa. Secondary structure and microstructure analyses revealed that the MBP structure was significantly damaged and that the β-sheet structure increased because of changes in the degree of aggregation between the protein molecules. Compared to the untreated MBPs, the MMBPs significantly improved the cooking quality and texture properties of the noodles, and the addition amount reached more than 6%, whereas that of the untreated MBPs was less than 3%. At this time, the cooking loss and the broken rate of the untreated MBPs group were about 2 times higher than that of the 6% MMBP-treated group. An analysis of changes in the water distribution, rheological properties, and microstructure revealed that intermolecular cross-linking occurred between the MMBPs and wheat dough, which improved the quality of the MMBP-treated noodles. The findings demonstrated that the MMBPs obtained by hydrothermal treatment had a positive effect on the wheat dough properties and noodle quality. These results provide a technical foundation for incorporating novel protein supplements into staple foods.

The Effectiveness of Clove Extract on Oxidization-Induced Changes of Structure and Gelation in Porcine Myofibrillar Protein

This study aimed to investigate the structural characteristics and gelation behavior of myofibrillar proteins (MPs) with or without clove extract (CE) at different oxidation times (0, 1, 3, and 5 h). Circular dichroism spectra and Fourier transform infrared spectra showed that samples with CE addition had significantly higher α-helix content after oxidation than those without CE addition. However, prolonged oxidation (5 h) would make the effect of CE addition less pronounced. Similarly, the ultraviolet-visible (UV) spectra analysis revealed that CE controlled the oxidative stretching of the protein tertiary structure and reduced the exposure of aromatic amino acids. In addition, the particle size and turbidity values of the CE group significantly decreased after oxidation compared to the non-CE group. CE increased the gel strength by 10.05% after 5 h of oxidation, which could be observed by scanning electron microscopy (SEM) as a more homogeneous, dense, less porous, network-like gel structure. Therefore, these results showed that oxidation induced significant changes in the structure and gel properties of MPs, but the addition of CE effectively inhibited these destructive changes.

Digestion characteristics of quinoa, barley and mungbean proteins and the effects of their simulated gastrointestinal digests on CCK secretion in enteroendocrine STC-1 cells

The demand for plant-based proteins has been rapidly increasing due to sustainability, ethical and health reasons. The present study aimed to investigate the digestion characteristics of three plant proteins (quinoa, barley and mungbean) based on an in vitro digestion model and the effect of their simulated gastrointestinal digests on satiety hormone cholecystokinin (CCK) secretion in enteroendocrine STC-1 cells. The nitrogen distribution in the digestion process, the relative molecular weight (MW) of peptides and the amino acid composition in simulated gastrointestinal digests were characterized. Quinoa protein had the highest proportion of soluble nitrogen after gastrointestinal digestion (85.79%), followed by barley protein (74.98%) and mungbean protein (64.14%), suggesting that quinoa protein was more easily digested than barley and mungbean proteins. The peptides but not free amino acids were the main components in the gastrointestinal digests of quinoa, barley, and mungbean proteins. The gastrointestinal digest of quinoa protein had a well balanced amino acid pattern, whereas that of barley protein was lacking Lys, and that of the mungbean protein was short of sulfur amino acids (Phe + Tyr) but rich in Lys. In terms of the ability to stimulate CCK secretion, the gastrointestinal digest of barley protein had a strong stimulatory effect on CCK secretion, while that of quinoa and mungbean proteins had only a weak stimulatory effect. After pretreatment with a specific calcium-sensing receptor (CaSR) antagonist NPS 2143, CCK secretion induced by the barley protein digest was greatly suppressed, indicating that CaSR was involved in barley protein digest-induced CCK secretion. These results show that quinoa protein has good nutritional quality, while barley protein is an excellent plant protein source to stimulate CCK secretion and has a potential application as a dietary supplement for obesity management.

Comparative structural and emulsifying properties of ultrasound-treated pea (Pisum sativum L.) protein isolate and the legumin and vicilin fractions

The structural properties, interfacial behavior, and emulsifying ability of ultrasound-treated pea protein isolate (PPI) and the legumin (11S) and vicilin (7S) globulin fractions prepared with a salt-solubilization procedure were investigated. Of the three protein groups, PPI was strongly responsive to ultrasound perturbation (20 kHz, 57-60 W·cm-2) showing the greatest solubility increase, particle size reduction, structure destabilization, and conformational change. Similar but less remarkable effects were observed on 11S globulins; 7S proteins, already highly soluble (>99%), were generally less sensitive to ultrasound. The ultrasound treatment significantly improved emulsifying activity, which resulted in greater emulsifying capacity and stronger interfacial adsorption for all protein samples. PPI exhibited the higher activity increase (70.8%) compared to approximately 30% for 11S and 7S. For both control and ultrasound treated proteins, the emulsifying capacity was in the order of 7S > 11S > PPI, inversely related to the trend of protein loading at the interface, indicating efficiency differences. The latter was attributed to emulsion clusters formed through protein-protein interaction in PPI and 11S emulsions which were visibly absent in 7S emulsions.

Effects of Ultrasound Combined with Preheating Treatment to Improve the Thermal Stability of Coconut Milk by Modifying the Physicochemical Properties of Coconut Protein

In the food industry, coconut milk has a unique flavor and rich nutritional value. However, the poor emulsifying properties of coconut proteins restrict its development. In this study, the effect of ultrasound combined with preheating on coconut globulin and coconut milk was evaluated by physicochemical properties and structural characteristics. The results showed that ultrasound and 90 °C preheating gave coconut protein better emulsifying and thermal properties, demonstrated by higher solubility (45.2% to 53.5%), fewer free sulfhydryl groups (33.24 to 28.05 μmol/g) and higher surface hydrophobicity (7658.6 to 10,815.1). Additionally, Fourier transform infrared spectroscopy and scanning electron microscopy showed obvious changes in the secondary structure. Furthermore, the change in the physicochemical properties of the protein brought a higher zeta potential (−11 to −23 mV), decreased the thermal aggregation rate (148.5% to 13.4%) and increased the viscosity (126.9 to 1103.0 m·Pa·s) of the coconut milk, which indicates that ultrasound combined with preheating treatment provided coconut milk with better thermal stability. In conclusion, ultrasound combined with preheating will have a better influence on modifying coconut globulin and increasing the thermal stability of coconut milk. This study provides evidence that ultrasound and other modification technologies can be combined to solve the problems encountered in the processing of coconut protein products.

Functional modification of grain proteins by dual approaches: Current progress, challenges, and future perspectives

Protein modification is a practical strategy to enhance the functional characteristics of proteins and broaden their commercial applications. Various chemical (e.g., pH-shifting, deamidation, succinylation), physical (e.g., sonication, high-speed shearing), or biological (e.g., microbial transglutaminase cross-linking, enzymatic hydrolysis) modification methods have frequently been employed to improve the functionality of native grain proteins. However, progress in intensification has led to the emergence of advanced methodologies, which involve the combination of modification techniques, generally known as "Dual Modification". This paper aims to comprehensively review the most recent researches focusing on the effects of dual modification on the functionality of grain proteins. Particular emphasis is given to elucidate the impact of this technique on physicochemical and structural properties. Furthermore, existing challenges and limitations associated with the utilization of this approach are highlighted, and prospects are proposed.

Study on the mechanism of enhanced gel strength of heat-induced egg white by shikimic acid braising

This study evaluated the effects and mechanism of shikimic acid braising on the gelling characteristics of heat-induced egg white gel (HEWG). The results indicated that, during braising, soluble protein and hardness showed an overall increasing trend. The absolute Zeta potential value showed a decreasing trend; however, T₂ and free sulfhydryl group showed an increasing trend first and decreasing trend later, and surface hydrophobicity showed a decreasing trend. Microstructure analysis showed that protein gel aggregation increased and that holes and cracks formed first, and then the cracks decreased. Fourier transform infrared spectrometry showed that shikimic acid could strengthen the polarity of HEWG, and a mutual transformation occurred between intramolecular β-sheets, intermolecular β-sheets, and intermolecular antiparallel β-sheets, as well as a slight blue-shift, in the α-helices. In general, the addition of shikimic acid could alter the HEWG structure and improve its gel strength, polarity, and aggregation. Moreover, the higher the concentration of shikimic acid, the greater the influence on HEWG. Therefore, shikimic acid could be used as a new type of gel enhancer for the modification of egg white gel.

Mechanism of ultrasound and tea polyphenol assisted ultrasound modification of egg white protein gel

In order to improve the characteristics of egg white protein gel and the stability of egg white protein gel products. In this work, the changes of the texture, physicochemical properties, secondary structure and microstructure of ultrasound modified egg white protein gel (UEP) and tea polyphenols (TP) assisted ultrasound modification of egg white protein gel (TUEP) with different ultrasonic power (0-360 W) were studied. With the increase of ultrasonic power, soluble protein, surface hydrophobicity and disulfide bonds of TUEP and UEP showed an increasing trend. In particular, with the increase of ultrasonic power, the content of intramolecular β-sheets and α-helices of TUEP showed an increasing trend, and significantly improved the relaxation time and microstructure, thus enhancing TUEP gel stability. In addition, the hardness and water holding capacity (WHC) of TUEP and UEP can be increased by ultrasonic treatment, and when the ultrasonic power reached 120 W, the hardness and WHC reached the maximum. The hardness and WHC of TUEP were significantly better than that of UEP. SDS-PAGE results showed that the peptide chain of protein without being broken under ultrasonic treatment. Ultrasonic treatment can improve the gel strength of egg white protein by promoting the cross-linking of proteins to form a dense gel structure, and egg white protein gel form more disulfide bonds and a more stable gel conformation under TP assisted ultrasound. In conclusion, ultrasound and TP assisted ultrasound modification of egg white protein gel is a reliable technique, which can improve the value of egg white protein in food processing.

Modifying the plant proteins techno-functionalities by novel physical processing technologies: a review

Plant proteins have recently gained market demand and momentum due to their environmentally friendly origins and health advantages over their animal-derived counterparts. However, their lower techno-functionalities, digestibility, bioactivities, and anti-nutritional compounds have limited their application in foods. Increased demand for physically modified proteins with better techno-functionalities resulted in the application of different thermal and non-thermal treatments to modify plant proteins. Novel physical processing technologies (NPPT) considered 'emerging high-potential treatments for tomorrow' are required to alter protein functionality, enhance bioactive peptide formations, reduce anti-nutritional, reduce loss of nutrients, prevention of damage to heat liable proteins and clean label. NPPT can be promising substitutes for the lower energy-efficient and aggressive thermal treatments in plant protein modification. These facts captivated the interest of the scientific community in designing novel functional food systems. However, these improvements are not verifiable for all the plant proteins and depend immensely on the protein type and concentration, other environmental parameters (pH, ionic strength, temperature, and co-solutes), and NPPT conditions. This review addresses the most promising approaches of NPPT for the modification of techno-functionalities of plant proteins. New insights elaborating the effect of NPPTs on proteins' structural and functional behavior in relation to other food components are discussed. The combined application of NPPTs in the field of plant-based bioactive functionalities is also explored.

Effect of Different Temperature-Controlled Ultrasound on the Physical and Functional Properties of Micellar Casein Concentrate

Micellar casein concentrate (MCC) is a novel dairy ingredient with high protein content. However, its poor functional properties impair its potential for further application, highlighting the importance of using innovative processing methods to produce modified MCC, such as ultrasound (US). This work investigated the impact of US on the physical and functional properties of MCC under temperature-controlled and -uncontrolled conditions for different time intervals. Under temperature-controlled ultrasound (TC-US) treatment, a reduction was found in the supernatant particle size of casein micelles. Soluble calcium content and hydrophobicity increased following ultrasound treatment at 20 °C, resulting in a remarkable improvement in emulsification. However, long-time ultrasonication led to an unstable state, causing the MCC solutions to show shear thinning behavior (pseudoplastic fluid). Compared with 50 °C temperature-controlled ultrasonication, ultrasonication at 20 °C had a greater influence on particle size, viscosity and hydrophobicity. These findings indicate that 20 °C TC-US could be a promising technology for the modification of MCC.

Effect mechanism of ultrasound pretreatment on fibrillation Kinetics, physicochemical properties and structure characteristics of soy protein isolate nanofibrils

Self-assembly of soy proteins into nanofibrils is gradually considered as an effective method to improve their technical and functional properties. Ultrasound is a non-thermal, non-toxic and environmentally friendly technology that can modulate the formation of protein nanofibrils through controlled structural modification. In this research, the effect of ultrasound pretreatment on soy protein isolate nanofibrils (SPIN) was evaluated by fibrillation kinetics, physicochemical properties and structure characteristics. The results showed that the optimum ultrasound condition (20% amplitude, 15 min, 5 s on-time and 5 s off-time) could increase the formation rate of SPIN by 38.66%. Ultrasound reduced the average particle size of SPIN from 191.90 ± 5.40 nm to 151.83 ± 3.27 nm. Ultrasound could increase the surface hydrophobicity to 1547.67 in the initial stage of nanofibrils formation, and extend the duration of surface hydrophobicity increased, indicating ultrasound could expose more binding sites, creating more beneficial conditions for nanofibrils formation. Ultrasound could change the secondary and tertiary structure of SPIN. The reduction of α-helix content of ultrasound-pretreated soy protein isolate nanofibrils (USPIN) was 12.1% (versus 5.3% for SPIN) and the increase of β-sheet content was 5.9% (versus 3.5% for SPIN) during fibrillation. Ultrasound could accelerate the formation of SPIN by promoting the unfolding of SPI, exposure of hydrophobic groups and formation of β-sheets. Microscopic images revealed that USPIN generated a curlier and looser shape. And ultrasound reduced the zeta potential, free sulfhydryl groups content and viscosity of SPIN. SDS-PAGE results showed that ultrasound could promote the conversion of SPI into low molecular weight peptides, providing building blocks for the nanofibrils formation. The results indicated that ultrasound pretreatment could be a promising technology to accelerate SPIN formation and promote its application in food industry, but further research is needed for the improvement of the functional properties of SPIN.

Ultrasound-modified interfacial properties and crystallization behavior of aerated emulsions fabricated with pH-shifting treated pea protein

The interfacial properties of pea protein isolate (NPP) were modified by pH12-shifting (BPP) and ultrasound treatment as a substitute for skimmed milk powder (SMP) in ice cream. The physicochemical properties and fat crystallization in emulsions before and after whipping were analyzed. Compared with SMP, the BPP emulsion displayed superior stability with small particle size and high viscosity. Fat clusters were observed in both SMP and BPP emulsions, which may promote the puncture and protrusion of fat crystals within droplets and lead to partial coalescence to allow air bubble entrapment. Aeration activity of BPP in cream was 1.5-fold that of NPP. Although the overrun value was smaller than SMP cream, the BPP cream retained the stable shape and had a slow melting rate due to its interactive dimensional network of fat. Ultrasound treatment was found to promote fat crystallization of emulsions, leading to the improved stability of final products.

Effects of ultrasound-assisted sodium bisulfite pretreatment on the preparation of cholesterol-lowering peptide precursors from soybean protein

In order to take full advantage of the gastrointestinal digestive function, the effects of S-type ultrasound-assisted sodium bisulfite (UASB) pretreatment on the preparation of cholesterol-lowering peptide precursors derived from soybean protein were investigated and the structural characterizations of pretreated proteins were explored. UASB pretreatment with the operational mode of mono-frequency ultrasound at 28 kHz, ultrasonic power density of 200 W/L and ultrasonic time of 50 min exhibited the highest cholesterol-lowering activity (56.90%) of soybean protein hydrolysates (SPH) after simulated gastrointestinal digestion, which increased by 87.17% compared to the control. Under these conditions, the peptide content of SPH after simulated gastrointestinal digestion was not significantly different (p > 0.05) compared to the control. Further FTIR analysis showed that UASB pretreatment increased β-turn and β-sheet content and decreased α-helix and random coil content. The changes in the surface hydrophobicity and microstructures of soybean protein indicated that UASB pretreatment loosened soybean protein structure and exposed more hydrophobic groups. SDS-PAGE indicated that the restriction sites changed after UASB pretreatment. In conclusion, UASB pretreatment is an efficient method for the preparation of cholesterol-lowering peptide precursors.

Interfacial dilatational and emulsifying properties of ultrasound-treated pea protein

In this study, the structural, interfacial, and emulsifying properties of high-intensity ultrasound (HUS)-treated pea protein isolate (PPI_US) were investigated. HUS at 50% amplitude and 57-60 W·cm^-2 for 5 min markedly improved protein solubility (by 132%), surface hydrophobicity (by 173%), and reduced particle size (by 52%). These physicochemical changes in PPI_US led to more rapid protein adsorption at the oil-water interface, improved emulsifying activity (by 18-27%) and capacity (by 11%), and enhanced emulsion physical stability. The multilayer nature, albeit less elastic, of the interfacial membrane formed by PPI_US when compared to control protein (PPI_C), based on dilatational testing, contributed to the above results. Moreover, PPI_US-stabilized emulsions exhibited a tendency of being less susceptible to lipid oxidation during storage. Thus, structure-modifying HUS may be a valuable processing technology for the manufacture of pea protein-based emulsion foods.