Effect of pH-shifting treatment on the structural and functional properties of soybean protein isolate and its interactions with (–)-epigallocatechin-3-gallate

Effects of different binding strategies of D-galactose and glycinin on the thermal gelation behavior of the composite system

In this study, non-covalent and covalent interactions between D-galactose (DG) and glycinin (11S) were induced using a pH-shift method. This approach represents an innovative advancement in existing protein-monosaccharide binding strategies. Furthermore, the study investigated the resulting changes in gel behavior and the properties of the composite thermal gels. The solubility and Zeta-potential analysis showed that the non-covalent interaction (S-11S/DG) was more stable and less dispersed than the covalent interaction (S/DG-11S). Rheological results showed that S-11S/DG has higher viscosity and can form stable elastic gel after temperature program. FTIR and intermolecular force results indicated that both gels utilized disulfide bonds as the primary covalent force, with additional chemical bonds playing a secondary role in maintaining the stability of the gel network and surrounding water molecules. However, the S/DG-11S exhibits a looser structure, resulting in a less elastic and thinner network structure. In contrast, the S-11S/DG gel network demonstrated increased elasticity and support, enhancing its hardness, cohesion and water holding capacity. Thus, the pH-shifting-induced non-covalent gel system had more stable network structure and better properties than the pH-shifting-induced covalent gel system. This study offered new insights for constructing soybean protein gel systems and advancing the design of novel soybean protein products.

Effect of H2O2 and pH on properties of myofibrillar proteins from Yak muscle during thermal gelation process

This paper examined the thermal gelation of yak myofibrillar protein (MP) incubated in a Fenton oxidation system at different pH values for 24 h. The effect of protein oxidation on the gel properties at different pH levels was explored by studying the water-holding capacity (WHC), solubility, texture, and other characteristics, while the chemical force, rheological, and microstructural variation in these conditions were analyzed. The results showed that protein oxidation negatively impacted the yak meat MP gel characteristics (p < 0.05). Increasing the H2O2 interval at different pH levels significantly decreased (p < 0.05) the WHC, solubility, and texture of the protein gel, the average reduction was 7.5%, 27.5%, 12.5% respectively. The H2O2 concentration and pH level substantially affected ionic and hydrogen bond formation (p < 0.05). Oxidation had the most obvious impact on the gel characteristics at pH 5.0. The MP gel displayed a loose, disordered microstructure with the lowest WHC, textural strength, storage modulus (G'), and intermolecular protein force. Oxidation had the least impact on the gel properties at pH 6.0. The MP gel exhibited the highest textural strength, G', and intermolecular forces, characterized by a compact, orderly microstructure with small, uniformly distributed pores. The gel displayed the best WHC after oxidation at pH 8.0.

Effect of pH-shifting combined with heat or ultrasonication treatment on physicochemical properties of quinoa protein isolates (QPI) dispersions

Quinoa protein isolate (QPI) offers a balanced amino acid profile but exhibits poor solubility, foaming, and emulsifying properties, limiting its broader use in food applications. This study evaluated the synergistic effects of pH-shifting (pH 2, 7, 10, and 12) combined with heat (50 °C) or sonication (20 kHz, 12.5 W, 30 min) on the structural and functional properties of QPI. The combination of pH-shifting at pH 12 with sonication achieved the highest solubility (~90 %), foaming capacity (~170 %), foaming stability (~45 %), and emulsifying performance (EAI: ~80 m2/g, ESI: ~35 min), outperforming either treatment alone. These enhancements were associated with reduced particle size (to ~40 nm), increased random coil content, and greater surface hydrophobicity, factors that improved protein flexibility and interfacial adsorption. Structural unfolding from extreme pH-shifting further amplified the effects of sonication through cavitation-induced disaggregation. This study demonstrates that combining alkaline pH-shifting with sonication is an effective strategy to improve QPI's technofunctional properties. The findings provide valuable insights for developing QPI as a functional, clean-label ingredient in plant-based emulsions, foams, and beverages. Future work should focus on interfacial characterization, sensory evaluation, and processing optimization to support industrial application.

Effects of pH shift and D-galactose on network structure of glycinin gel and diffusion behavior of non-network proteins

To reduce the content of non-network proteins in protein-based gels, a synergistic approach involving pH shift and D-galactose (DG) was developed herein to obtain elastic gels with dense networks. The results revealed that the combined effect of pH shift and DG promoted the formation of additional disulfide bonds and chemical bonds between molecules, resulting in a denser, and highly elastic gel network, which immobilized more aggregates, leading to a significant reduction in non-network protein content, and enhancing the functional properties of the gel. Moreover, non-network proteins primarily consisted of subunit A4 (mostly Glu and Asp), while the subunit B was the primary polypeptide forming the gel network. Therefore, the removal of the non-network protein has no significant effect on the microstructure, water holding capacity, elasticity, and recovery of the gel. Comprehensively, the combination of pH shift and DG generated a positive synergistic effect of the glycinin hydrogel network structure.

Soluble nano-sized aggregates of Alaska pollock proteins engineered by the refolding process of pH-shifting

Alaska pollock proteins (PPs) are aquatic proteins with a compact structure, which leads to poor solubility and limited application in food industries. This study explored the structural assembly and gelation behavior of the PP-soluble aggregates prepared by the refolding processing of acidic (pH 1.5-7) or alkaline (pH 12-7) pH-shifting treatment. PPs refolded at alkali pHs produced more soluble aggregates than at acid pHs. Lots of myosin heavy lights (MHCs) could interact with actin to form soluble aggregates at high pH rather than low pH. When shifting back to pH 7, the solubility of alkaline-shifted PPs was boosted to over 60% with a more flexible structure, while acidic-shifted PPs showed reduced solubility (29%) with increased rigidity. Molecular characteristics results indicated that alkaline-shifted PPs comprising MHCs and actin exhibited higher surface hydrophobicity and sulfhydryl groups. These structural modifications induced by alkaline pH-shifting contributed to improving the gelling, emulsifying and foaming properties of PPs. Intriguingly, both acidic- and alkaline-shifted PPs showed a retarded digestive behavior. These novel insights may be adaptable to other animal proteins for modulating the protein structure-functionality, expanding their applications in food industries.

Recent advances in the plant protein-polyphenol interactions for the stabilization of emulsions

Proteins from plant sources including legumes, cereals and oilseeds are gaining attention due to their suitability for sustainable production, functionality, and positive consumer perception. On the other hand, polyphenols (PPs) are receiving considerable attention as natural ingredients in the human diet due to their potent antioxidant and anti-inflammatory properties. Recent studies indicate that the emulsifying properties of plant proteins (PLPs) can be improved after modification through covalent and/or non-covalent interactions with PPs due to the changes in the conformation and/or the surface chemistry of the proteins. Complexes formed between PLPs-PPs can serve as innovative ingredients for developing novel food products with modified textural properties. Also, Pickering emulsions, multiple emulsions, multilayer emulsions, nanoemulsions, and high internal phase emulsions can be stabilized by such systems to deliver bioactive compounds. This paper reviews the most recent research on the PLP-PP interactions and their role in the stabilization of various emulsion-based systems. A special emphasis is given to modifying the structure and functionality of PLPs and PPs. The challenges and opportunities of applying PLP-PP interactions in emulsion-based systems are also highlighted.

Soy protein-polyphenols conjugates interaction mechanism, characterization, techno-functional and biological properties: An updated review

Soy protein is a promising nutritional source with improved functionality and bioactivities due to conjugation with polyphenols (PP)-the conjugates between soy protein and PP held by covalent and noncovalent bonds. Different approaches, including thermodynamics, spectroscopy, and molecular docking simulations, can demonstrate the outcomes and mechanism of these conjugates. The soy protein, PP structure, matrix properties (temperature, pH), and interaction mechanism alter the ζ-potential, secondary structure, thermal stability, and surface hydrophobicity of proteins and also improve the techno-functional properties such as gelling ability, solubility, emulsifying, and foaming properties. Soy protein-PP conjugates also reveal enhanced in vitro digestibility, anti-allergic, antioxidant, anticancer, anti-inflammatory, and antimicrobial activities. Thus, these conjugates may be employed as edible film additives, antioxidant emulsifiers, hydrogels, and nanoparticles in the food industry. Future research is needed to specify the structure-function associations of soy protein-PP conjugates that may affect their functionality and application in the food industry.

Effect of partial substitution of NaCl by KCl on aggregation behavior and gel properties of beef myosin

Based on the three typical gels under KCl substitution groups, the effect of partial substitution of NaCl by KCl (groups: T 1:0.6 M NaCl; T 2: 0.3 M NaCl +0.3 M KCl; T 3: 0.2 M NaCl +0.4 M KCl; T 4:0.6 M KCl) on the aggregation behavior and gel characteristics of myosin was evaluated. The significant changes in hydrophobicity and sulfhydryl content (P < 0.05) indicate KCl substitution enhances myosin aggregation through hydrophobic interactions and disulfide bonds. According to Ca2+-ATP, scanning electron microscopes (SEM) and the rheological results, T2 had a smoother network structure at about 75 °C. Noticeably, T3 had high water holding capacity (WHC), but its gel had some visible cavities. T4 had a gel structure with several irregular aggregates due to a greater aggregation rate. Thus, appropriate partial substitution of NaCl by KCl could enhance beef myosin gel properties and heat-induced aggregation behavior.

Response surface optimization of protein extraction from cold-pressed terebinth (Pistacia terebinthus L.) oil byproducts: Physicochemical and functional characteristics

The current study focused on optimizing the extraction parameters of terebinth seed proteins from cold-pressed terebinth oil byproducts to maximize protein purity and protein yield. The isolated proteins were characterized to evaluate their properties; thus revealing the valorization potential of these byproducts. Response surface methodology was used to detect the effect of three extraction parameters (pH, temperature, and time). The protein isolates were studied for their physicochemical and functional characteristics. The results indicated that an extraction pH of 8, a temperature of 50°C, and an extraction period of 60 min are optimum conditions for obtaining protein isolates with the highest purity. On the other hand, it was demonstrated that an extraction pH of 12, a temperature of 46.4°C, and an extraction duration of 102.4 min were optimum conditions for the maximum protein yield. The proteins produced under these two sets of conditions, referred to as TRP (terebinth protein with maximum purity) and TRY (terebinth protein with maximum yield), respectively, exhibited comparable oil absorption capacity (OAC), foaming, emulsifying capabilities, and stability. Both proteins showed the highest solubility at pH 11, and their zeta potentials approached zero at pH 4, indicating proximity to their isoelectric points. However, FRAP and DPPH assays showed that TRP and TRY offered low antioxidative capacity. The high β-sheet content in TRP and TRY suggests enhanced thermal stability but reduced digestibility of these proteins. Therefore, in addition to protein enrichment, TRP and TRY protein isolates can be utilized in muffins and other food applications thanks to their favorable oil absorption, foaming and emulsifying capacities, and thermal stabilities.

Quercetin on the properties of rice bran oil body: Focused surface charge, oxidative stability and digestive properties

To further enhance the stability of rice bran oil body (RBOB) emulsions, this study examined the impact of various concentrations of quercetin (QU) on the microstructure, rheological properties, oxidative stability, and digestive properties of RBOB emulsions. The results indicated that by incorporating QU concentration, the particle size of RBOB emulsions could be significantly reduced to 300 nm; QU could improve the surface hydrophobicity, the emulsifying activity index and emulsification stability index of RBOB emulsions of 550, 0.078 m2/g and 50.78 min, respectively; the storage stability of RBOB emulsions was further improved; the higher concentration of QU could delay the oxidation of RBOB emulsions, among which, the 500 μmol/L concentration inhibited the strongest effect of oil oxidation. It also improved the thermal stability of RBOB emulsions. After gastrointestinal digestion, the free fatty acids release rate of RBOB emulsions with QU addition decreased to 14.68%, and RBOB emulsions were slowly hydrolyzed. Therefore, adding QU to RBOB helps to improve its stability and delay digestion.

Effects of the covalent conjugation between caffeic acid and peanut allergen protein Ara h1 on the antigenicity and structure of Ara h1

Ara h1 was the highest content of peanut allergen protein, identified as a biomarker of peanut allergen. In this study, Ara h1 was covalently complexed with caffeic acid (CA) to research the effects of covalent conjugation on the antigenicity and protein structural properties of Ara h1. After the covalent complexing of Ara h1 and CA, the IgG-binding capacity of Ara h1 was reduced compared with that of control Ara h1. Moreover, the structure of Ara h1 changed from ordered to disordered, the number of intermolecular hydrogen bonds decreased, and some hydrophobic groups were exposed or hydrophobic peptides were released. The carboxyl group in CA reacted with the amino group in Ara h1. The digestibility of Ara h1-CA was increased. The antigenicity of Ara h1-CA was undetectable after 30 min of digestion in vitro. These findings can serve as a reference for further research on hypoallergenic peanut products.

Structure, functional and physicochemical properties of lotus seed protein under different pH environments

BACKGROUND

The present study investigated the structure, functional and physicochemical properties of lotus seed protein (LSP) under different pH environments. The structures of LSP were characterized by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, Fourier transform infrared spectroscopy (FTIR), zeta potential, particle size distributions, free sulfhydryl and rheological properties. The functional and physicochemical properties of LSP were characterized by color, foaming property, emulsification property, solubility, oil holding capacity, water holding capacity, differential scanning calorimetry analysis and surface hydrophobicity.

RESULTS

LSP was mainly composed of eight subunits (18, 25, 31, 47, 51, 56, 65 and 151 kDa), in which the richest band was 25 kDa. FTIR results showed that LSP had high total contents of α-helix and β-sheet (44.81-46.85%) in acidic environments. Meanwhile, there was more β-structure and random structure in neutral and alkaline environments (pH 7.0 and 9.0). At pH 5.0, LSP had large particle size (1576.98 nm), high emulsion stability index (91.43 min), foaming stability (75.69%) and water holding capacity (2.21 g g-1), but low solubility (35.98%), free sulfhydryl content (1.95 μmol g-1) and surface hydrophobicity (780). DSC analysis showed the denaturation temperatures (82.23 °C) of LSP at pH 5.0 was higher than those (80.10, 80.52 and 71.82 °C) at pH 3.0, 7.0 and 9.0. The analysis of rheological properties showed that LSP gel had high stability and great strength in an alkaline environment.

CONCLUSION

The findings of the present study are anticipated to serve as a valuable reference for the implementation of LSP in the food industry. © 2024 Society of Chemical Industry.

Cryoprotective effect of epigallocatechin gallate replacing sucrose on Hypophythalmichthys molitrix surimi during frozen storage

BACKGROUND

The present study aimed to investigate the cryoprotective effect of epigallocatechin gallate (EGCG) replacing sucrose on surimi during frozen storage. Substitution or partial substitution of 0.1% EGCG for sucrose (1.5%) was added to surimi, and the surimi samples without and with commercial cryoprotectants (4% sucrose and 4% sorbitol) were used as the control group.

RESULTS

The results obtained suggest that, with the increase in frozen storage time, the structural performance of surimi protein gradually weakened (e.g. the decrease in the surface hydrophobicity, the increase in the total sulfhydryl and solubility, and the protein myosin heavy chain bands became shallow) and surimi gel quality gradually deteriorated (e.g. the decrease in water-holding capacity, gel strength and all texture profile attributes). However, compared with the other three group surimi samples during the frozen period, the surimi proteins with partial replacement of sucrose by EGCG had a higher total sulfhydryl group content and solubility of proteins, as well as lower surface hydrophobicity of protein, suggesting that the addition of EGCG as a partial substitute for sucrose can enhance the antifreeze ability of surimi. Meanwhile, the surimi gel with the partial replacement of sucrose by EGCG had a higher water retention capacity, gel strength and texture attributes (e.g. hardness, springiness, cohesiveness, chewiness, and resilience), indicating that the addition of EGCG as a partial substitute for sucrose can inhibit the deterioration of surimi gel quality.

CONCLUSION

Overall, EGCG partially replacing sucrose can play an alternative cryoprotectant with a lower sweetness to prevent the quality of surimi from deteriorating. © 2024 Society of Chemical Industry.

Enhancing the functionality of pea proteins by conjugation with propylene glycol alginate via transacylation reaction assisted with ultrasonication

Pea proteins lack the desirable functional characteristics for food and beverage applications. In this study, transacylation reaction assisted with ultrasonication was used to glycate pea proteins with propylene glycol alginate to enhance their functional properties. The reaction was carried out at pH 11.0 for different pea protein isolate: propylene glycol alginate mass ratios and time durations in a sonic bath at 40 °C. Glycation was confirmed in gel electrophoresis, and ultrasonication enhanced the glycation, with optimal degrees of glycation observed at 45 min reaction time and mass ratios of 2:1 (37.73%) and 1:1 (35.96%). The transacylation reaction increased random coil content of pea proteins by 28% and enhanced their solubility by 2.02 times at pH 7.0, water holding capacity by >50% at pH 7.0, foaming properties, emulsifying properties, and heat stability. This study offers a novel approach that can enhance functionality and applicability of pea proteins.

Modification of hordein by gallic acid in ethanol-free environments: Impact of covalent and non-covalent interactions on structure, physicochemical properties and self-assembly

The objectives of this study were to modify hordein with gallic acid (GA) in alcohol-free media and to compare the impact of covalent and non-covalent binding on the properties of hordein. Covalent hordein-GA complexes (H-GA) and non-covalent hordein/GA complexes (H/GA) were distinguished by molecular weight, free sulfhydryl groups and free amino groups. Isothermal titration calorimetry (ITC) demonstrated that physical mixing induced non-covalent binding of GA to hordein via hydrogen bonding and hydrophobic interactions, with a lower binding efficiency than covalent ones. Both complexation types led to a structural shift of hordein toward disorder, while grafting of oligomeric GA and alkaline treatment resulted in lower surface hydrophobicity and higher antioxidant activity of H-GA compared to H/GA. The nanoparticles assembled from H-GA had smaller particle sizes and higher physical stability than those formed from H/GA. The results of this study may provide new insights into the modification of hordein by polyphenols.

A comprehensive review on the recent trends in extractions, pretreatments and modifications of plant-based proteins

Plant-based proteins offer sustainable and nutritious alternatives to animal proteins with their techno-functional attributes influencing product quality and designer food development. Due to the inherent complexities of plant proteins, proper extraction and modifications are vital for their effective utilization. This review highlights the emerging sources of plant-based proteins, and the recent statistics of the techniques employed for pretreatment, extraction, and modifications. The pretreatment, extraction and modification approach to modify plant proteins have been classified, addressed, and the recent applications of such methodologies are duly indicated. Furthermore, this study furnishes novel perspectives regarding the potential impacts of emerging technologies on the intricate dynamics of plant proteins. A thorough review of 100 articles (2018-2024) shows the researchers' keen interest in investigating novel plant proteins and how they can be used; seeds being the main source for protein extraction, followed by legumes. Use of by-products as a protein source is increasing rapidly, which is noteworthy. Protein studies still lack knowledge on protein fraction, antinutrients, and pretreatments. The use of physical methods and their combination with other techniques are increasing for effective and environmentally friendly extraction and modification of plant proteins. Several studies explore the effect of protein changes on their function and nutrition, especially with a goal of replacing ingredients with plant proteins that have improved or enhanced qualities. However, the next step is to investigate the sophisticated modification methods for deeper insights into food safety and toxicity.

Experimental investigation into the implications of low-intensity magnetic field treatment on the structural and functional properties of rapeseed meal during biofermentation

The functionality of rapeseed meal is limited, to acquire more utilization, the functional attributes were improved by altering its structural features using magnetic field-assisted solid fermentation. The magnetic treatment was performed every 24 h (specifically at 24, and 48 h), each treatment having a duration of 4 h. The magnetic intensity was set at 120 Gs, and the fermentation temperature 37 °C. Magnetic field-assisted solid fermentation resulted in higher surface hydrophobicity, fluorescence intensity, UV absorption, and sulfhydryl groups of rapeseed meal. Magnetic field treatment considerably enhanced solubility, antioxidant activity, emulsifying activity, and stability by 8.8, 19.5, 20.7, and 12.3 %, respectively. Magnetic field-assisted solid fermentation also altered rapeseed meal structure, as shown by scanning electron microscopy, atomic force microscopy, and Raman spectroscopy outcomes. Correlation analysis displayed positive interrelationships between functional characteristics, and surface hydrophobicity, β-sheets, and polydispersity index.

Unveiling the critical pH values triggering the unfolding of soy 7S and 11S globulins and enhancing their encapsulation efficiency

The pH-shifting process is an effective encapsulation method, and it is typically performed at extreme alkaline pH, which severely limits the application. In this study, we found that there were critical pH for the unfolding proteins during pH-shifting from 7 to 12, and upon the critical pH, physiochemical characteristics of protein greatly changed, leading to a sharp increase of encapsulation of hydrophobic actives. Firstly, the critical pH for β-conglycinin (7S) or Glycinin (11S) unfolding was determined by multispectral technology. The critical pH for 7S and 11S were 10.5 and 10.3, respectively. The encapsulation efficiency (EE) obtained by β-conglycinin-curcumin nanocomposite (7S-Cur) (88.80 %) and Glycinin-curcumin nanocomposite (11S-Cur) (88.38 %) at critical pH was significantly higher than that obtained by pH 7 (7S-Cur = 16.66 % and 11S-Cur = 15.78 %), and both values were close to EE obtained by at 12 (7S-Cur = 95.16 % and 11S-Cur = 94.63 %). The large-scale application of hydrophobic functional compounds will be enhanced by the experimental results.

pH-regulated Tannic acid and soybean protein isolate adhesive for enhanced performance in plant-based meat analogues

A food adhesive comprising tannic acid (TA) and soybean protein isolate (SPI) was developed to establish a cohesive bond between soy protein gel and simulated fat. The impact of varying TA concentrations and pH levels on the adhesive's rheology, thermal stability, chemical structure, and tensile strength were investigated. Rheological results revealed a gradual decrease in adhesive viscosity with increasing TA content. Differential scanning calorimetry (DSC) and thermal gravimetric (TG) results indicated that the stability of the adhesive improved with higher TA concentrations, reaching its peak at 0.50% TA addition. The incorporation of TA resulted in the cross-linking of amino group in unfolded SPI molecules, forming a mesh structure. However, under alkaline conditions (pH 9), adhesive viscosity and stability increased compared to the original pH. This shift was due to the disruption of the SPI colloidal charge structure, an increase in the stretching of functional groups, further unfolding of the structure, and an enhanced binding of SPI to TA. Under the initial pH conditions, SPI reacted with TA's active site to form covalent crosslinked networks and hydrogen bonds. In alkaline condition, beyond hydrogen and ionic bonding, the catechol structure was oxidized, forming an ortho-quinone that crosslinked SPI and created a denser structure. Tensile strength measurements and freeze-thaw experiments revealed that the adhesive exhibited maximum tensile strength and optimal adhesion with 0.75% TA at pH 9, providing the best overall performance. This study provides a new formulation and approach for developing plant-based meat analogues adhesives.

Self-assembly and aggregation behavior of temperature-controlled modified glycinin and d-galactose colloidal particles

The molecular structure and morphologies of complex colloidal particles with modified glycine (S-11S) and d-galactose were studied by multispectral, microscopic imaging and chromatographic techniques at different temperatures, and the self-assembly and aggregation mechanisms were determined. Overall, high-temperature-treated S-11S and d-galactose associate at cysteine and phenylalanine sites and self-assemble into colloidal particles of greater stability than glycinin and S-11S via ionic and disulfide bonds. The structure and subunit content of composite colloidal particles were changed. Assessing the sub-microstructure reveals that temperature can regulate the directional aggregation of complex colloidal particles. The elasticity of the complex colloidal particles is maximum enhanced at 95 ℃ as confirmed by the rheological. Thus, the heat-treated aggregation of the soy protein and its complex was evaluated to provide a new theoretical basis for the application of soy protein in gels and other areas and contribute to the design of new soy protein products.

Multi-spectroscopic and molecular docking studies for the pH-dependent interaction of β-lactoglobulin with (-)-epicatechin gallate and/or piceatannol: Influence on antioxidant activity and stability

(-)-Epicatechin gallate (ECG) and piceatannol (PIC) are commonly polyphenols with excellent biological activities. β-Lactoglobulin (BLG) is a food-grade globule protein and its morphologies are sensitive to pH. This study used experimental and computational methods to determine the interaction of single or combined ECG and PIC with BLG at different pHs. The static quenching process was determined through fluorescence and ultraviolet-visible spectroscopy. Compared with ECG, PIC could significantly bind to BLG with higher affinity. Their binding affinity for BLG with different morphologies followed the tendency of monomer > dimer > tetramer. The negative contribution of van der Waals forces, electrostatic interactions, and hydrogen bonds to ΔHo exceeded the positive contribution of hydrophobic interactions in the spontaneous and exothermic process. The reduced binding affinity in the ternary systems demonstrated the competitive binding between ECG and PIC on BLG, and the hinder effect of ECG or PIC was enhanced with increasing pH. Molecular docking studies revealed the same binding sites of ECG and PIC on various conformations of BLG and identical driven forces as thermodynamic results. Tryptophan and tyrosine were the main participators in the BLG + ECG and BLG + PIC systems, respectively. The conformational changes in the binary and ternary systems could be ascertained through synchronous fluorescence, circular dichroism, and dynamic light scattering. Furthermore, the effects of pH and BLG encapsulation on the antioxidant capacity and stability of ECG or PIC were also implemented. ECG or PIC was the most stable in the (BLG + PIC) + ECG system at pH 6.0. This study could clarify the interaction mechanism between ECG/PIC and BLG and elucidate the pH effect on their binding information. The results will provide basic support for their usage in food processing and applications.

Effect of epigallocatechin-3-gallate modification on the structure and emulsion stability of rice bran protein in the presence of soybean protein isolate

For improving the emulsion stability of rice bran protein (RBP), RBP was modified by different concentrations of epigallocatechin-3-gallate (EGCG) in the presence of soybean protein isolate (SPI), and RBP-EGCG-SPI conjugate was prepared by alkaline pH-shifting. The results showed that the addition of EGCG led to an increase in the bound phenol content and the flexibility of the secondary structure, a decrease in the free sulfhydryl and disulfide bond content of the RBP-EGCG-SPI conjugate. EGCG covalently bound to RBP and SPI through non-disulfide bonds. When the concentration of EGCG was 10 % (w/v), the emulsifying activity index and emulsion stability index of conjugate reached the maximum value (36.61 m2/g and 255.61 min, respectively), and the conjugate had the best emulsion stability. However, an EGCG concentration above 10 % (w/v) negatively affected the emulsion stability, with increasing particle size due to protein aggregation. Summarily, the modification of EGCG improved the emulsion stability of conjugate by regulating the spatial structure of RBP-EGCG-SPI conjugate. The work provided an important guide to further improve the emulsion stability of RBP.

Artificial oil bodies: A review on composition, properties, biotechnological applications, and improvement methods

In order to simulate the structure of natural oil body, artificial oil bodies (AOBs) are fabricated by the integration of oleosins, triacylglycerols (TAGs) and phospholipids (PLs) in vitro. Recently, AOBs have gained great research interest both in the food and biological fields due to its ability to act as a novel delivery system for bioactive compounds and as a carrier for target proteins. This review aims to summarize the composition and the preparation methods of AOBs, examine the factors influencing their stability. Moreover, this contribution focusses on exploring the application of AOBs to encapsulate functional ingredients that are prone to oxidation as well as improve efficiency involved in protein purification, renaturation and immobilization by reducing the complex steps. In addition, the improvement measures to further enhance the stability and efficacy of AOBs are also discussed. The application of AOBs is expected to be a big step towards replacing existing bioreactors and delivery systems.

EGCG-based nanoparticles: synthesis, properties, and applications

(-)-Epigallocatechin-3-gallate (EGCG) is a natural phenolic substance found in foods and beverages (especially tea) that exhibits a broad spectrum of biological activities, including antioxidant, antimicrobial, anti-obesity, anti-inflammatory, and anti-cancer properties. Its potential in cardiovascular and brain health has garnered significant attention. However, its clinical application remains limited due to its poor physicochemical stability and low oral bioavailability. Nanotechnology can be used to improve the stability, efficacy, and pharmacokinetic profile of EGCG by encapsulating it within nanoparticles. This article reviews the interactions of EGCG with various compounds, the synthesis of EGCG-based nanoparticles, the functional attributes of these nanoparticles, and their prospective applications in drug delivery, diagnosis, and therapy. The potential application of nanoencapsulated EGCG in functional foods and beverages is also emphasized. Top-down and bottom-up approaches can be used to construct EGCG-based nanoparticles. EGCG-based nanoparticles exhibit enhanced stability and bioavailability compared to free EGCG, making them promising candidates for biomedical and food applications. Notably, the non-covalent and covalent interactions of EGCG with other substances significantly contribute to the improved properties of these nanoparticles. EGCG-based nanoparticles appear to have a wide range of applications in different industries, but further research is required to enhance their efficacy and ensure their safety.

Effect of pectin concentration on emulsifying properties of black soldier fly (Hermetia illucens) larvae albumin modified by pH-shifting and ultrasonication

The effect of pectin concentration on the structural and emulsifying properties of black soldier fly larvae albumin (BSFLA) modified by pH-shifting (pH12) and ultrasound (US) was studied. The results (intrinsic fluorescence, surface hydrophobicity, Fourier transform infrared spectrum, and disulfide bonds) showed that modified BSFLA samples, especially pH12-US, were more likely to bind to pectin through hydrogen bonding, electrostatic interactions, and hydrophobic interactions due to the unfolding of BSFLA, the collapse of disulfide bonds and exposure of hydrophobic groups. Thus, a BSFLA-pectin complex with smaller particle size, more negative charges, and a relatively loose structure was formed. The emulsifying activity (EAI) and stability index (ESI) of pH12-US modified BSFLA were significantly enhanced by the addition of pectin, reaching the highest values (associated with 174.41 % and 643.22 % increase, respectively) at pectin concentration of 1.0 %. Furthermore, the interface modulus of the emulsion prepared by the modified BSFLA was mainly viscous, and had higher apparent viscosity, smaller particle size and droplet size, contributing to higher EAI and ESI. The study findings suggest the addition of pectin to pH12-US treated BSFLA could be used in industry to prepare BSFLA-pectin emulsion with exceptional/desirable properties.

Plant protein solubility: A challenge or insurmountable obstacle

Currently, there is an increasing focus on comprehending the solubility of plant-based proteins, driven by the rising demand for animal-free food formulations. The solubility of proteins plays a crucial role in impacting other functional properties of proteins and food processing. Consequently, understanding protein solubility in a deeper sense may allow a better usage of plant proteins. Herein, we discussed the definition of protein solubility from both thermodynamic and colloidal perspectives. A range of factors affecting solubility of plant proteins are generalized, including intrinsic factors (amino acids composition, hydrophobicity), and extrinsic factors (pH, ionic strength, extraction and drying methods). Current methods to enhance solubility are outlined, including microwave, high intensity ultrasound, hydrostatic pressure, glycation, pH-shifting, enzymatic hydrolysis, enzymatic cross-linking, complexation and modulation of amino acids. We base the discussion on diverse modified methods of nitrogen solubility index available to determine and analyze protein solubility followed by addressing how other indigenous components affect the solubility of plant proteins. Some nonproteinaceous constituents in proteins such as carbohydrates and polyphenols may exert positive or negative impact on protein solubility. Appropriate protein extraction and modification methods that meet consumer and manufacturers requirements concerning nutritious and eco-friendly foods with lower cost should be investigated and further explored.

Structure and functionality of whey protein, pea protein, and mixed whey and pea proteins treated by pH shift or high-intensity ultrasound

Three modifications (pH shift, ultrasound, combined pH shift and ultrasound) induced alterations in pure whey protein isolate (WPI), pea protein isolate (PPI), and mixed whey and pea protein (WPI-PPI) were investigated. The processing effect was related to the protein type and technique used. Solubility of WPI remained unchanged by various treatments. Particle size was enlarged by pH shift while reduced by ultrasound and combined approach. All methods exposed more surface hydrophobic groups on WPI, while pH shift and joint processing was detrimental to its emulsifying activity. The PPI and mixture exhibited similar responses toward the modifications. Solubility of PPI and the blend enhanced in the sequence of pH shift and ultrasound > ultrasound > pH shift. Individual approach expanded while co-handling diminished the particle diameter. Treatments also caused more disclosure of hydrophobic regions in PPI and WPI-PPI and emulsifying activity was ameliorated in the order of pH shift and ultrasound > ultrasound > pH shift.

Effect of pH-shifting on the water holding capacity and gelation properties of mung bean protein isolate

In this study, alkaline pH-shifting modified the globular structure of mung bean protein isolate (MBPI) to form flexible and stretched structures. In contrast, acidic pH-shifting increased the rigidity of MBPI. The increased flexibility (at the level of the secondary structure) and newly exposed intermolecular amino acid groups induced by alkaline pH-shifting improved the water holding capacity and gelation properties of proteins. Specifically, MBPI treated at pH 12 (MP12) showed the most flexible structure and highest water holding capacity and gel formation properties (least gelation concentration). The water-holding capacity of native MBPI increased from 1.56 g/g to 4.81 g/g, and its least gelation concentration decreased from 22 % to 15 % by pH-shifting at pH 12. Furthermore, MP12 formed stronger and more elastic heat-induced gels than native MBPI. We identified significant differences in the structural properties and water holding capacity, and gelation properties of acidic and alkaline pH-shifted MBPI and investigated the gelation properties of MP12 including rheological and morphological analyses. Our findings can facilitate the use of mung beans as a protein source in a wide range of food applications, including plant-based and processed meats.

Techno-functional attributes of oilseed proteins: influence of extraction and modification techniques

Plant-based protein isolates and concentrates are nowadays becoming popular due to their nutritional, functional as well as religious concerns. Among plant proteins, oilseeds, a vital source of valuable proteins, are continuously being explored for producing protein isolates/concentrates. This article delineates the overview of conventional as well as novel methods for the extraction of protein and their potential impact on its hydration, surface properties, and rheological characteristics. Moreover, proteins undergo several modifications using physical, chemical, and biological techniques to enhance their functionality by altering their microstructure and physical performance. The modified proteins hold a pronounced scope in novel food formulations. An overview of these protein modification approaches and their effects on the functional properties of proteins have also been presented in this review.

Redesign of air/oil-water interface via physical fields coupled with pH shifting to improve the emulsification, foaming, and digestion properties of plant proteins

The application of plant proteins in food systems is largely hindered by their poor foaming or emulsifying properties and low digestibility compared with animal proteins, especially due to the aggregate state with tightly folded structure, slowly adsorbing at the interfaces, generating films with lower mechanical properties, and exposing less cutting sites. Physical fields and pH shifting have certain synergistic effects to efficiently tune the structure and redesign the interfacial layer of plant proteins, further enhancing their foaming or emulsifying properties. The improvement mechanisms mainly include: i) Aggregated plant proteins are depolymerized to form small protein particles and flexible structure is more easily exposed by combination treatment; ii) Particles with appropriate surface properties are quickly adsorbed to the interfacial layer, and then unfolded and rearranged to generate a tightly packed stiff interfacial layer to enhance bubble and emulsion stability; and iii) The unfolding and rearrangement of protein structure at the interface may result in the exposure of more cutting sites of digestive enzymes. This review summarizes the latest research progress on the structural changes, interfacial behaviors, and digestion properties of plant proteins under combined treatment, and elucidates the future development of these modification technologies for plant proteins in the food industry.

Determination of the critical pH for unfolding water-soluble cod protein and its effect on encapsulation capacities

Hydrophobic polyphenols, with a variety of physiological activities, are often practically limited due to their low water solubility and chemical instability, among which curcumin (Cur) is a representative hydrophobic polyphenol. To improve Cur, the cod protein (CP)-Cur composite particles (CP-Cur) were successfully prepared using the pH-shift method, but this pH-shift method (7-12-7) required a higher pH, which limited application and increased cost. The critical pH of CP structure unfolding during pH-shift and its encapsulation effect on Cur were investigated in this paper. During the pH-shift process, the critical pH of the structural unfolding of CP was pH 10, and the degree of protein structure unfolding was higher, which was attributed to the increasing electrostatic repulsion, and the weakened hydrogen bond and hydrophobic interaction. The encapsulation efficiency of CP-Cur formed after pH 10-shift was higher than that formed after pH 9.8-shift, which increased by 22.17 %. At pH 9.8, the binding sites in CP reached saturation at the molar ratio of 10, while at pH 10 and 10.2, the binding sites in CP both reached saturation at the molar ratio of 14, also indicating that the protein treated with critical pH could bind more Cur. The binding between Cur and CP was mostly hydrophobic interaction, accompanied by hydrogen bonding and electrostatic interactions. The above results verified the necessity of critical pH in the experiment, indicating that critical pH could indeed improve the encapsulation effect and obtain a higher encapsulation efficiency. This work will help improve the large-scale application of hydrophobic functional substances in production.

Plant-Based Meat Proteins: Processing, Nutrition Composition, and Future Prospects

The growing need for plant-based meat alternatives promotes the rapid progress of the food industry. Processing methods employed in plant-based meat production are critical to preserving and enhancing their nutritional content and health benefits, directly impacting consumer acceptance. Unlike animal-based food processing, the efficiency of protein extraction and processing methods plays a crucial role in preserving and enriching the nutritional content and properties. To better understand the factors and mechanisms affecting nutrient composition during plant-based meat processing and identify key processing steps and control points, this work describes methods for extracting proteins from plants and processing techniques for plant-based products. We investigate the role of nutrients and changes in the nutrients during plant protein product processing. This article discusses current challenges and prospects.

Plant-Based Protein-Phenolic Interactions: Effect on different matrices and in vitro gastrointestinal digestion

This review summarizes the literature on the interaction between plant-based proteins and phenolics. The structure of the phenolic compound, the plant source of proteins, matrix properties (pH, temperature), and interaction mechanism (covalent and non-covalent) change the secondary structure, ζ-potential, surface hydrophobicity, and thermal stability of proteins as well as their functional properties including solubility, foaming, and emulsifying properties. Studies indicated that the foaming and emulsifying properties may be affected either positively or negatively according to the type and concentration of the phenolic compound. Protein digestibility, on the other hand, differs depending on (1) the phenolic concentration, (2) whether the food matrix is ​​solid or liquid, and (3) the state of the food-whether it is heat-treated or prepared as a mixture without heat treatment in the presence of phenolics. This review comprehensively covers the effects of protein-phenolic interactions on the structure and properties of proteins, including functional properties and digestibility both in model systems and real food matrix.

Soy protein interactions with polyphenols: Structural and functional changes in natural and cationized forms

Herein, cationic soy protein (NSPI) was synthesized by grafting Ethylenediamine (EDA) onto soy protein isolate (SPI), and protein-gallic acid (GA) complexes were formed by mixing NSPI with GA in various ratios. We assessed the structure, particle size, thermal stability, emulsifying ability, and antioxidant capacity of NSPI and complexes. Results show that grafting with EDA introduced a positive charge to SPI and resulted in a uniform particle size, and enhanced thermal stability, emulsifying ability, and antioxidant capacity. In addition, NSPI presented more amino groups and stronger interactions with GA compared to SPI. EDA and GA synergistically increased the flexibility of SPI, reducing the α-helix content and increasing the random coil content. Moreover, the interactions between SPI, NSPI, and GA were static, and hydrophobic and electrostatic between GA and SPI and NSPI, respectively. Grafting SPI with EDA improved functionality and interactions with GA, implying that NSPI-GA complexes may function as emulsifiers and antioxidants.

Comparison of proanthocyanidins A2 and B2 on IgE-reactivity and epitopes in Gly m 6 using multispectral, LC/MS-MS and molecular docking

This study comparatively analyzed the changes in IgE-reactivity and epitopes in proanthocyanidins A2- (PA-Gly m 6) and B2-Gly m 6 (PB-Gly m 6) conjugates prepared by alkali treatment at 80 °C for 20 min. Similar to the western blot, ELISA also showed a higher reduced IgE-reactivity in PA-Gly m 6 (70.12 %) than PB-Gly m 6 (63.17 %). SDS-PAGE demonstrated that proanthocyanidins A2 caused more formation of >180 kDa polymers than proanthocyanidins B2. Multispectral analyses revealed that PA-Gly m 6 exhibited more structural alteration (e.g., a decrease of α-helical content and ANS fluorescence intensity) to unfold protein structure than proanthocyanidins B2, improving the accessibility to modify Gly m 6 for shielding or destroying conformational epitopes. LC/MS-MS revealed that PA-Gly m 6 conjugates had a lower abundance of allergens, peptides and linear epitopes than PB-Gly m 6 conjugates. Molecular docking showed that proanthocyanidins A2 and B2 reacted with Gln-317 and Asn-94 of epitopes, respectively. Overall, proanthocyanidins A2 is more effective than proanthocyanidins B2 to decrease the IgE-reactivity of Gly m 6 due to more shielding or destruction of conformational epitopes and lower content allergens and linear epitopes, which was attributed to more protein-crosslinks formation and structural changes in PA-Gly m 6 conjugates.

Pulsed electric field improves the EGCG binding ability of pea protein isolate unraveled by multi-spectroscopy and computer simulation

Understanding molecular mechanisms during protein modification is critical for expanding the application of plant proteins. This study investigated the conformational change and molecular mechanism of pea protein isolate (PPI) under pulsed electric field (PEF)-assisted (-)-Epigallocatechin-Gallate (EGCG) modification. The flexibility of PPI was significantly enhanced after PEF treatment (10 kV/cm) with decrease (23.25 %) in α-helix and increase (117.25 %) in random coil. The binding constant and sites of PEF-treated PPI with EGCG were increased by 2.35 times and 10.00 % (308 K), respectively. Molecular docking verified that PEF-treated PPI had more binding sites with EGCG (from 4 to 10). The number of amino acid residues involved in hydrophobic interactions in PEF-treated PPI-EGCG increased from 5 to 13. PEF-treated PPI-EGCG showed a significantly increased antioxidant activity compared to non-PEF-treated group. This work revealed the molecular level of PEF-assisted EGCG modification of PPI, which will be significant for the application of PPI in food industry.

Impacts of Industrial Modification on the Structure and Gel Features of Soy Protein Isolate and its Composite Gel with Myofibrillar Protein

Native soy protein isolate (N-SPI) has a low denaturation point and low solubility, limiting its industrial application. The influence of different industrial modification methods (heat (H), alkaline (A), glycosylation (G), and oxidation (O)) on the structure of SPI, the properties of the gel, and the gel properties of soy protein isolate (SPI) in myofibril protein (MP) was evaluated. The study found that four industrial modifications did not influence the subunit composition of SPI. However, the four industrial modifications altered SPI's secondary structure and disulfide bond conformation content. A-SPI exhibits the highest surface hydrophobicity and I_850/830 ratio but the lowest thermal stability. G-SPI exhibits the highest disulfide bond content and the best gel properties. Compared with MP gel, the addition of H-SPI, A-SPI, G-SPI, and O-SPI components significantly improved the properties of the gel. Additionally, MP-ASPI gel exhibits the best properties and microstructure. Overall, the four industrial modification effects may impact SPI's structure and gel properties in different ways. A-SPI could be a potential functionality-enhanced soy protein ingredient in comminuted meat products. The present study results will provide a theoretical basis for the industrialized production of SPI.

The alteration of composition, conformation, IgE-reactivity and functional attributes in proanthocyanidins-soy protein 7S conjugates formed by alkali-heating treatment: Multi-spectroscopic and proteomic analyses

This study assessed the alteration of IgE-reactivity and functional attribute in soy protein 7S-proanthocyanidins conjugates (7S-80PC) formed by alkali-heating treatment (pH 9.0, 80 °C, 20 min). SDS-PAGE demonstrated that 7S-80PC exhibited the formation of >180 kDa polymers, although the heated 7S (7S-80) had no changes. Multispectral experiments revealed more protein unfolding in 7S-80PC than in 7S-80. Heatmap analysis showed that 7S-80PC showed more alteration of protein, peptide and epitope profiles than 7S-80. LC/MS-MS demonstrated that the content of total dominant linear epitopes was increased by 11.4 % in 7S-80, but decreased by 47.4 % in 7S-80PC. As a result, Western-blot and ELISA showed that 7S-80PC exhibited lower IgE-reactivity than 7S-80, probably because 7S-80PC exhibited more protein-unfolding to increase the accessibility of proanthocyanidins to mask and destroy the exposed conformational epitopes and dominant linear epitopes induced by heating treatment. Furthermore, the successful attachment of PC to soy 7S protein significantly increased antioxidant activity in 7S-80PC. 7S-80PC also showed higher emulsion activity than 7S-80 owing to its high protein flexibility and protein unfolding. However, 7S-80PC exhibited lower foaming properties than 7S-80. Therefore, the addition of proanthocyanidins could decrease IgE-reactivity and alter the functional attribute of the heated soy 7S protein.

Study on the Structure, Function, and Interface Characteristics of Soybean Protein Isolate by Industrial Phosphorylation

The impacts of industrial phosphorylation on the structural changes, microstructure, functional, and rheological features of soybean protein isolate (SPI) were spotlighted. The findings implied that the spatial structure and functional features of the SPI changed significantly after treatment with the two phosphates. Sodium hexametaphosphate (SHMP) promoted aggregation of SPI with a larger particle size; sodium tripolyphosphate (STP) modified SPI with smaller particle size. SDS-polyacrylamide gel electrophoresis (SDS-PAGE) results showed insignificant alterations in the structure of SPI subunits. Fourier transform infrared (FTIR) and endogenous fluorescence noted a decline in α-helix quantity, an amplification in β-fold quantity, and an increase in protein stretching and disorder, indicating that phosphorylation treatment fluctuated the spatial structure of the SPI. Functional characterization studies showed that the solubility and emulsion properties of the SPI increased to varying degrees after phosphorylation, with a maximum solubility of 94.64% for SHMP-SPI and 97.09% for STP-SPI. Emulsifying activity index (EAI) and emulsifying steadiness index (ESI) results for STP-SPI were better than those for SHMP-SPI. Rheological results showed that the modulus of G' and G″ increased and the emulsion exhibited significant elastic behavior. This affords a theoretical core for expanding the industrial production applications of soybean isolates in the food and various industries.

Multi-spectral and proteomic insights into the impact of proanthocyanidins on IgE binding capacity and functionality in soy 11S protein during alkali-heating treatment

This study evaluated the impact of proanthocyanidins on immunoglobulin E (IgE) binding capacity, antioxidant, foaming and emulsifying properties in soy 11S protein following alkali treatment at 80 °C for 20 min. The formation of >180 kDa polymer was observed in the combined heating and proanthocyanidins-conjugation treatment sample (11S-80PC) rather than in the heating treated sample (11S-80) using sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). The structural analyzes demonstrated that 11S-80PC exhibited more protein unfolding than 11S-80. Heatmap analysis revealed that 11S-80PC had more alteration of peptide and epitope profiles in 11S than in 11S-80. Molecular docking showed that PC could well react with soy protein 11S. Liquid chromatography tandem MS analysis (LC/MS-MS) demonstrated that there was a 35.6 % increase in 11S-80, but a 14.5 % decrease in 11S-80PC for the abundance of total linear epitopes. As a result, 11S-80PC exhibited more reduction in IgE binding capacities than 11S-80 owing to more obscuring and disruption of linear and conformational epitopes induced by structural changes. Moreover, 11S-80PC exhibited higher antioxidant capacities, foaming properties and emulsifying activity than 11S-80. Therefore, the addition of proanthocyanidins could decrease allergenic activity and enhance the functional properties of the heated soy 11S protein.

Investigation of the differences in the effect of (-)-epigallocatechin gallate and proanthocyanidins on the functionality and allergenicity of soybean protein isolate

In this study, the differences in effects of (-)-epigallocatechin gallate (EGCG) and proanthocyanidins (PC) on the functionality and allergenicity of soybean protein isolate (SPI) were studied. SDS-PAGE demonstrated that SPI-PC conjugates exhibited more high-molecular-weight polymers (>180 kDa) than SPI-EGCG conjugates. Structural analysis showed that SPI-PC conjugates exhibited more disordered structures and protein-unfolding, improving the accessibility of PC to modify SPI, compared to SPI-EGCG conjugates. LC/MS-MS demonstrated that PC caused more modification of SPI and major soybean allergens than EGCG, resulting in a lower abundance of epitopes. The successful attachment of EGCG and PC to SPI significantly increased antioxidant capacity in conjugates. Furthermore, SPI-PC conjugates exhibited greater emulsifying activity and lower immunoglobulin E (IgE) binding capacity than SPI-EGCG conjugates, which was attributed to more disordered structure and protein-unfolding in SPI-PC conjugates. It is implied that proanthocyanidins may be promising compounds to interact with soybean proteins to produce functional and hypoallergenic foods.

Molecular structural modification of β-conglycinin using pH-shifting with ultrasound to improve emulsifying properties and stability

This present work underlines the effect of pH-shifting at pH 2 and pH 12 individually or combined with ultrasound treatment to modify the molecular structure of β-conglycinin (7S) on its emulsifying properties and stability. Fourier transform infrared (FTIR) spectroscopy and intrinsic fluorescence spectroscopy showed that pH-shifting improves the molecular structure of 7S, while ultrasound further promotes structural changes. In particular, the pH-shifting at pH 12 combined with ultrasound treatment (U-7S-12) resulted in more significant changes than the pH-shifting at pH 2 combined with ultrasound (U-7S-2). U-7S-12 showed a significant reduction in protein particle size from 152 to 34.77 nm and a relatively smooth protein surface compared to 7S. The protein had the highest surface hydrophobicity and flexibility at 81,560.0 and 0.45, respectively, and the free sulfhydryl content from 1.57 to 2.02 μmol/g. In addition, we characterized the emulsions prepared after 7S treatment. The single or combined treatment increased the interfacial protein adsorption of the samples, which showed lower viscosity and shear stress compared to 7S. The U-7S-12 emulsion exhibited the highest emulsifying properties and was more stable than other emulsions under creaming, heating, and freeze-thaw conditions. In summary, the concerted action of pH-shifting and ultrasound can modify the structure, and combined alkaline pH-shifting and ultrasound treatment can further improve the emulsifying properties and stability of 7S.

Changes in IgE binding capacity, structure, physicochemical properties of peanuts through fermentation with Bacillus natto and Lactobacillus plantarum along with autoclave pretreatment

This study investigated the immunoglobulin E (IgE) binding capacity, structure, and physicochemical properties of raw crushed peanut (RCP) after fermentation with Lactobacillus plantarum and Bacillus natto along with autoclaved pretreatment. SDS-PAGE showed the disappearance of partial protein (>45 kDa) in autoclaved peanuts (ACP) and fermented autoclaved peanuts with L. plantarum (LP), and of majority protein (>14.4 kDa) in fermented autoclaved peanuts with B. natto (BN) or a mixture of L. plantarum and B. natto (LPBN). Structural analysis revealed protein-aggregation and protein-unfolding in autoclaved and fermented peanuts, respectively. Indirect ELISA demonstrated that the IgE binding capacities in ACP, LP, BN and LPBN were reduced by 11.3%, 20.6%, 78.7% and 90.2%, respectively, compared to RCP. LPBN showed the lowest IgE binding capacity due to the highest masking and destruction of epitopes and exhibited the desirable physicochemical properties simultaneously. Mixed strain fermentation has the potential to produce hypoallergenic peanut products.

Explore the Interaction between Ellagic Acid and Zein Using Multi-Spectroscopy Analysis and Molecular Docking

With the increasing interest in value-added maize products, the interaction of zein with bioactive molecules to become more nutritional and beneficial to human health has gained a lot of attention. To broaden the application of ellagic acid (EA) in maize flour products, we investigated the interaction between zein and EA. The fluorescence quenching type of zein interacting with EA was mainly static quenching through hydrophobic interaction, as demonstrated by quenching behavior modeling, and ultraviolet-visible spectroscopy confirmed the formation of zein–EA complexes. Synchronous fluorescence spectroscopy showed that EA reduced the polarity of zein around tyrosine residues, which were exposed to a more hydrophobic microenvironment. Meanwhile, circular dichroism suggested that EA noticeably changed the secondary structure of zein, which was mainly reflected in the increase of α-helix and β-sheet content and the decrease of random coil content. Finally, the molecular docking simulation found that zein could have five active sites binding to EA and there was hydrogen bond interaction besides hydrophobic interaction. The findings of this study provided a basis for a theory for the interaction mechanism between zein and EA, which could be essential for developing value-added plant-derived protein products using EA as a functional component.