Properties Of Soy Protein Isolate Research Articles

Revealing the interaction mechanism and emulsion properties of carboxymethyl cellulose on soy protein isolate at different pH

In this study, carboxymethyl cellulose (CMC) was introduced to reduce the instability and poor functional properties of soy protein isolate (SPI) in low pH environment. The SPI–CMC systems containing 0–0.5% CMC were prepared at pH 4.0 and 5.0. By exploring the interaction mechanism between them, the optimal formation conditions of the composite systems were revealed. The results showed that CMC was continuously adsorbed on the surface of SPI at pH 4.0, in which electrostatic behavior and hydrogen bonds played an important role. The emulsion properties were the best at 0.4% CMC, and the emulsion activity index (EAI) and emulsion stability index (ESI) were increased by 48.91 m2/g and 91.41 min compared with SPI emulsion. The optical microscope images showed that the emulsion interfacial proteins were formed and the droplets were evenly distributed at 0.4% CMC. At pH 5.0, the stability of the SPI–CMC systems was highly dependent on the steric hindrance and high viscosity of CMC. The EAI and ESI of the emulsion at 0.5% CMC were the highest, which increased by 49.08 m2/g and 83.79 min compared with SPI emulsion. The optical microscope images confirmed that the addition of 0.5% CMC significantly inhibited the leakage of oil droplets. In conclusion, this study provides an effective strategy for stabilizing SPI emulsion in low pH environments, which has important practical application value.

Characteristic of the interaction mechanism between soy protein isolate and functional polysaccharide with different charge characteristics and exploration of the foaming properties

The commercial production process will partially damage the foaming properties of soy protein isolate (SPI). Adding functional polysaccharides have a positive effect on the foaming properties of SPI, but the effects are affected by several factors. For this reason, three kinds of polysaccharides with different charges, including chitosan (CS, a cationic polysaccharide), guar gum (GUG, a neutral polysaccharide) and gellan gum (GEG, an anionic polysaccharide), were complexed with SPI at different mass ratios to discuss their interaction mechanism, and the foaming properties of these complexes were preliminarily explored. After complexation, the structure of SPI was further folded and interacted with three polysaccharides mainly through non-covalent bonding. Specifically, SPI and CS interacted through weak electrostatic interaction, volume exclusion effect and hydrogen bonding at a high CS concentration. SPI and GEG interacted through strong electrostatic interaction and hydrogen bonding. However, SPI and GUG interacted only through hydrogen bonding. In addition to SPI/CS10, the foamability of SPI/polysaccharide complexes was significantly lower than single SPI. By contrast, the foam stability of all the complexes was much higher than single SPI, and increased with the increase of the polysaccharide concentration, among which the SPI/GEG complexes showed the highest foam stability. These findings provided the interaction mechanism between SPI and polysaccharides with different charges, and the complexes with outstanding foam stability can be used for improving the stability and texture of aerated foods.

Characteristics of soy protein hydrolysate nanofibrils and their stabilization mechanism for Pickering emulsion: Interfacial properties, Rheology and stability

Enzymatic hydrolysis is an effective method to improve the physicochemical properties of soy protein isolate (SPI) nanofibrils and expand their application in stabilizing Pickering emulsion. In this work, the effects of enzymatic hydrolysis on the SPI fibrillation and the stabilization mechanisms of SPI hydrolysate nanofibrils for Pickering emulsion were investigated. According to sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) images and Thioflavin T (ThT) fluorescence data, a higher degree of hydrolysis (DH) contributed to releasing more small molecular weight peptides (mainly from α, α′, and β subunits) to improve apparent rate constant and surface hydrophobicity during fibrillation. When DH increased to 8%, SPI hydrolysate could form long and flexible nanofibrils and possessed the highest content of β-sheet (21.40%), when heated for 12 h. Enzymatic hydrolysis played various positive impacts on the interfacial properties of nanofibrils, including faster interfacial adsorption and near-neutral wettability (92.87°). SPI hydrolysate nanofibrils could impart enhanced gel-like structure and exceptional thermal stability to Pickering emulsions, resulting in a decrease in droplet size from 52.06 μm to 32.74 μm. This work will enhance the exploration of the formation mechanism of nanofibrils and broaden their application in the functional emulsion.

Influence of heat treatment before and/or after high-pressure homogenization on the structure and emulsification properties of soybean protein isolate

This study investigates the effects of heat treatment before high-pressure homogenization (HHPH) and heat treatment after high-pressure homogenization (HPHH) at different pressures (20, 60, and 100 MPa) on the structural and emulsification properties of soy protein isolate (SPI). The results indicate that HHPH treatment increases the surface hydrophobicity (H0) of the SPI, reduces β-fold and irregular curls, leading to the formation of soluble aggregates, increased adsorbed protein content, and subsequent improvements in emulsification activity index (EAI) and emulsion stability index (ESI). In contrast, the HPHH treatment promoted the exchange of SH/SS bonds between protein molecules and facilitated the interaction of basic peptides and β-subunits, leading to larger particle sizes of the soluble aggregates compared to the HHPH-treated samples. However, excessive aggregation in HPHH-treated aggregates leads to decreased H0 and adsorbed protein content, and increased interfacial tension, negatively affecting the emulsification properties. Compared to the HPHH treatment, HHPH treatment at homogenization pressures of 20 to 100 MPa increases EAI and ESI by 5.81–29.6 % and 5.31–25.9 %, respectively. These findings provide a fundamental basis for soybean protein manufacturers to employ appropriate processing procedures aimed at improving emulsification properties.

Investigating the functional properties of soy protein isolate conjugated with oxidized basil seed gum through Maillard reaction in food systems

Investigating the functional properties of soy protein isolate conjugated with oxidized basil seed gum through Maillard reaction in food systems

Tannic acid-loaded halloysite clay grafted with silver nanoparticles enhanced the mechanical and antimicrobial properties of soy protein isolate films for food-packaging applications

Poor mechanical and water barrier properties restrict the applicability of protein-based packaging in high-moisture food commodities. In this study, a nanocomposite (Nc) of tannic acid-loaded halloysite nanotubes grafted with silver nanoparticles was developed as a reinforcement agent to enhance the functional properties of soy protein isolate (SPI)-based films. The 5%- and 10%-Nc incorporation in SPI films significantly (p < 0.05) improved the tensile strength (by 1.94–3.14 fold) and thermal stability (by 5–7%) and reduced water vapor permeability (by 1.28–1.30 fold), oxygen permeability (by 2.72–3.84 fold), and water solubility (by 6.3–9.5 fold). The 5%- and 10% Nc/SPI films showed antioxidant properties (by scavenging 18%−28% of DPPH) and exhibited a 3–5 log10 reduction in multi-drug resistant S. aureus and S. Typhimurium contamination in chicken breast fillets. Although 10% Nc/SPI exhibited silver migration to chicken fillets beyond the acceptable limit contributing to color change, 5% Nc/SPI films enhanced the shelf-life of fillets for 4 days by facilitating a controlled pH, lipid oxidation, and microbial growth with acceptable levels of silver migration. In conclusion, the multifunctionality of Nc in SPI films enables its potential to be an alternative to non-biodegradable and non-eco-friendly polymers.

Structural, mechanical, antioxidant and antibacterial properties of soy protein isolate (SPI)-based edible food packaging films as influenced by nanocellulose (NC) and green extracted phenolic compounds from date palm leaves

This study investigated the addition of cellulose nanoparticles (NC) and green extracted phenolic compounds from date palm leaves (DLE) as reinforcing and bioactive agent, respectively, into the soy protein isolate (SPI) edible films. Structural, physiochemical, optical, mechanical, barrier, thermal, and bioactive properties of the films were explored. The incorporation of NC improved the SPI film’s physiochemical, mechanical, and barrier properties but did not show effect on the antioxidant and antibacterial properties. Following the incorporation of DLE in liquid form (DLWE) the film’s antioxidant and antibacterial properties significantly increased but due to the presence of natural deep eutectic solvent (NADES) (plasticizer) all other properties were negatively affected. However, enriching the SPI-NC films with DLE in powder form (DLPE) improved the bioactive properties while maintaining the improved mechanical and barrier properties. These findings indicated that SPI-NC/DLPE films exhibited improvements in the whole performance and provided promising strategy for formulation of biodegradable packaging films. This approach is an effective strategy towards sustainable utilization of unexplored agricultural wastes (date palm leaves derived NC and phenolic compounds) for development of active and environmentally friendly food packaging material.

Characterization of structural and functional properties of soy protein isolate and sodium alginate interpenetrating polymer network hydrogels.

This study used enzymatic and Ca2+ cross-linking methods to prepare edible soy protein isolate (SPI) and sodium alginate (SA) interpenetrating polymer network hydrogels to overcome the disadvantages of traditional interpenetrating polymer network (IPN) hydrogels, such as poor performance, high toxicity, and inedibility. The influence of changes in SPI and SA mass ratio on the performance of SPI-SA IPN hydrogels was investigated. Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) were used to characterize the structure of the hydrogels. Texture profile analysis (TPA), rheological properties, swelling rate, and Cell Counting Kit-8 (CCK-8) were used to evaluate physical and chemical properties and safety. The results showed that, compared with SPI hydrogel, IPN hydrogels had better gel properties and structural stability. As the mass ratio of SPI-SA IPN changed from 1:0.2 to 1:1, the gel network structure of hydrogels also tended to be dense and uniform. The water retention and mechanical properties of these hydrogels, such as storage modulus (G'), loss modulus (G"), and gel hardness increased significantly and were greater than those of the SPI hydrogel. Cytotoxicity tests were also performed. The biocompatibility of these hydrogels was good. This study proposes a new method to prepare food-grade IPN hydrogels with mechanical properties of SPI and SA, which may have strong potential for the development of new foods. © 2023 Society of Chemical Industry.

Physiochemical characteristics and sensory properties of plant protein isolates-konjac glucomannan compound gels.

In this study, the effects of konjac glucomannan (KGM) at different concentrations on the physiochemical and sensory properties of soy protein isolate (SPI), pea protein isolate (PPI), or peanut protein isolate (PNPI) compound gels were investigated. The results revealed that when the ratio of PNPI to KGM was 90:10, the denaturation temperature of PNPI could be significantly enhanced to 119.32°C by KGM modification. Concerning the textural and microstructural features, the amount of KGM addition had positive correlation with the hardness and chewiness of each compound gel, however, too much KGM addition will cause the unstable internal structure of the PNPI/KGM compound gels (70:30 and 60:40). Furthermore, sensory results indicated that PNPI/KGM (80:20), PPI/KGM (80:20), SPI/KGM (80:20) had great potential to be considered as prototypes for novel plant-based products, which generated the highest acceptance scores of 5.04, 5.94, and 5.36 in each group, respectively.

Improving gel properties of soy protein isolate through alkaline pH-shifting, mild heat treatment, and TGase cross-linking

Improving the functional properties of soybean protein isolate (SPI) is essential for expanding its applications in food-related fields, given its poor solubility and gelation. This study investigated the effect of alkaline pH-shifting and mild heating on the structure of SPI, as well as the gel properties after TGase cross-linking. Solubility of SPI increased with increasing alkalinity from pH 7.0 to 12.0 at 25 °C, accompanied by decreased particle size and increased surface hydrophobicity. At pH 12.0 and 50 °C, SPI showed the highest solubility, smallest particle size, and best surface hydrophobicity. Intrinsic fluorescence spectra revealed that the protein structure unfolded after combined treatment, exposing more hydrophobic groups. TGase cross-linking modified SPI exhibited significantly increased gel hardness and water holding power. Therefore, alkaline pH transfer combined with mild heating treatment has great potential for generating functional modified SPI and provides a simple and easy method for preparing SPI with diverse gel and structural properties.

Binding effects of piceatannol and oxyresveratrol on the structural and functional properties of soy protein isolate

Piceatannol (PIC), oxyresveratrol (OXY), and soy protein isolate (SPI) are essential dietary molecules. This study evaluated the interaction between PIC/OXY and SPI using multiple spectroscopic techniques and molecular docking simulations. The static quenching mechanism was confirmed by steady-state fluorescence, Förster resonance energy transfer (FRET), and time-resolved fluorescence (TRF) spectroscopy. The binding affinity of PIC to SPI was stronger than that of OXY, and the interactions were spontaneous and exothermic. The subtle change in the secondary structure of SPI after the addition of PIC or OXY can be ascertained by analyzing the surface hydrophobicity, sulfhydryl group content, particle size, zeta potential, and α-helical content. The emulsifying and foaming properties of SPI were enhanced after complexing with PIC/OXY. The thermodynamic parameters and molecular docking results demonstrated that PIC and OXY bound to SPI at the same sites, and that van der Waals forces (vdW forces) and hydrogen bonding (H-bonding) were the main interaction forces. In addition, the results also showed that the encapsulation of SPI can enhance the antioxidant activity of PIC and OXY. The in vitro gastrointestinal digestion of PIC and OXY in the absence or presence of SPI was evaluated. This study can be used as a reference for further research on the digestion and absorption of SPI−PIC/OXY complexes and as a guide for healthy diets.

Influence of silylated nano cellulose reinforcement on the mechanical, water resistance, thermal, morphological and antibacterial properties of soy protein isolate (SPI)-based composite films

The aim of this research work is to improve the mechanical and water-resistance properties of soy protein isolate (SPI) biofilm. In this work, 3-aminopropyltriethoxysilane (APTES) coupling-agent modified nanocellulose was introduced into the SPI matrix in the presence of citric acid cross-linker. The presence of amino groups in APTES facilitated the formation of - cross-linked structures with soy protein. The incorporation of a citric acid cross-linker made the cross-linking process more productive, and the surface smoothness of the film was confirmed by a Scanning Electron Microscope (FE-SEM). From the study of the mechanical and thermal properties and water resistance of the film, it was confirmed that the results were highly satisfactory for the modified nanocellulose-incorporated film compared to the non-modified one. Additionally, coating of citral essential oil onto SPI nanocomposite film displayed antimicrobial properties due to the presence of various phenolic groups in the citral oil. The Tensile Strength and Young's Modulus of silane-modified nanocellulose containing film were enhanced by ∼119 % and ∼ 112 %, respectively on incorporation of 1 % APTES-modified nanocellulose. Consequently, this work is expected to offer an effective way for silylated nano-cellulose reinforcing soy protein isolate (SPI)-based bio nanocomposite films for packaging applications. As an example, we have demonstrated one of the applications as wrapping films for packing black grapes.

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 I850/830 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.

Effect of atmospheric pressure non-thermal pin to plate cold plasma on structural and functional properties of soy protein isolate

The atmospheric cold plasma (ACP) effect on food macromolecules is a current area of interest in the non-thermal processing of food science researchers. The present study investigates the effect of atmospheric pressure non-thermal pin-to-plate ACP processing on the structural and functional properties of Soy Protein Isolate (SPI). The hydrated SPI liquid samples were treated at different input voltages, 170V, 200V, and 230 V, at different time intervals of 05, 10 and 15 min at room temperature. The primary and secondary structures of the protein were estimated by SDS-PAGE and FTIR. The protein morphological changes were observed by scanning electron microscope. The Differential Scanning Calorimetry system was used to determine the thermal property of treated proteins. Rheological pasting, in vitro enzymatic digestion, trypsin inhibition, water holding and solubility properties were observed on 09 samples of ACP-treated SPI. The primary structure was found unaffected. The treatment could alter β -turns and β -sheet's secondary protein structure by altering double bond region intensity. The enhancement of the surface area, etching phenomenon and aggregation were observed in electron micrographs. ACP reduced Protein denaturation temperature from 215.05 ± 0.30 °C to 209.05 ± 0.66 °C. The initial viscosity (40 °C) of water-based untreated SPI suspension samples 16.17 ± 1.7 cP increased significantly to 42.82 ± 0.5 cP in higher-level ACP-treated SPI suspension samples. ACP processed protein post-digestion amino acid quantity enhanced from 3.33 ± 0.46 μg/mL to 14.90 ± 0.52 μg/ml, which could be due to the reduction of trypsin inhibition activity up to 59.00 ± 0.004%. Treated protein water holding capacity and solubility increased to 62.74 ± 0.08% from 58.18 ± 0.14%. Hence, ACP technology can be a promising solution for minimally processed, chemical-free food process technic to modify the protein techno-functional properties for enhanced product quality and digestibility.

Functional, structural properties and interaction mechanism of soy protein isolate nanoparticles modified by high-performance protein-glutaminase

Investigating the changes in the structural and functional properties of soy protein isolate (SPI) modified by high-performance protein-glutaminase (PG) and understanding their interactions are crucial for the application of SPI nanoparticles. Herein, the thermal stability and activity of PG were evolved by computer-assisted rational design strategy, generating the best variant Z15 (N16M/N20L/Q21H/K48R/S81E/T113E) with a 4.65-fold improved activity (75.57 U/mg) and increased thermal stability (ΔTm = 4.6 °C), one of the best performing PG. SPI treated with Z15 showed better solubility, foaming, and emulsifying properties than the wild type PG-deamidation, which were increased by 1.25-fold, 45.45%, and 38.95%, respectively. Furthermore, SPI treated with Z15 exhibited lower hardness and higher cohesiveness. By systematically analyzing the structural characteristics, SPI nanoparticles possessed a coarse, loose, and porous microstructure. Molecular dynamics simulations suggested that the Glu81 and Glu113 residues of Z15 contributed the most to the stabilization interaction in β-conglycinin-Z15 complexes. These results could provide theoretical guidance for the potential application of SPI nanoparticles in sustainable green plant-based foods industries.

Particle characteristics and tribo-rheological properties of soy protein isolate (SPI) dispersions: Effect of heating and incorporation of flaxseed gum

To understand the heat treatment and flaxseed gum (FG) on the properties of commercial spray dried soy protein isolate (SPI), SPI dispersions were prepared with mass ratio of 6 %, 9 %, and 12 % in water and the corresponding protein concentrations of 2.2 %, 3.61 % and 5.23 % were reached after centrifugation. The solutions were treated at different temperatures (25, 75 and 100 °C) and the particle characteristics and physical properties of the resulted samples were determined. The influence of different concentrations (0.05 % to 0.3 %) of FG addition was evaluated in the SPI solution at 5 % protein concentration. The results showed that heating caused decrease of particle size of the SPI proteins and 100 °C heat treatment caused decrease of hydrophobicity and viscosity of the protein dispersions, and increase of their physical stability, and the effect was more marked at high protein concentration; while heat treatment at 75 °C caused substantial increase in protein hydrophobicity and viscosity, and decrease of stability. Addition of FG resulted in increase of particle size, absolute value of zeta potential and hydrophobicity of the protein solutions. The viscosity of the solution was decreased with addition of FG, but higher FG concentration could lead to higher viscosity. The physical stability of the mixed system was improved at low FG concentrations, but decreased at concentration higher than 0.2 %, which was more significant after 100 °C heat treatment. FG incorporation could improve the boundary lubrication of the protein solutions.

Improvement of the encapsulation capacity and emulsifying properties of soy protein isolate through controlled enzymatic hydrolysis

Self-assembling nanoparticle made from soy protein hydrolysates has proved to be a promising delivery system due to its excellent biocompatibility and synthetic feasibility. In this study, the critical parameters that control the SPI hydrolysate structure and its encapsulation capacity have been assessed. Three different enzymes, including Flavorzyme, Neutrase and Alcalase, were selected to hydrolyze soy protein isolate (SPI), and a solvent evaporation method was used to fabricate β-carotene loaded nanoparticles. Microstructure observation, SDS-PAGE, surface hydrophobicity, and endogenous fluorescence analysis were carried out to examine the key structural factors influencing encapsulation efficiency of SPI hydrolysates nanoparticles (SPIHs). It was found moderate exposure of hydrophobic amino acids inside the 7 S globulin via Flavorzyme controlled hydrolysis can increase the surface hydrophobicity of SPIH, therefore improving its emulsifying properties, while excessive hydrolysis of 7 S by Alcalase would cause weak hydrophobic interactions between the hydrophobic amino acids, which restricted the binding site with β-carotene. Above results provide a foundation for fabricating nanoparticles encapsulating lipophilic compounds with high encapsulation rate from SPI hydrolysates (SPIH).

Effects of catechin types found in tea polyphenols on the structural and functional properties of soybean protein isolate–catechin covalent complexes

Soy protein isolate (SPI) has useful functional properties, such as gelation, emulsification, and foaming. However, SPI is usually dense and has a unique spherical structure, which hinders its practical application. In this study, the effects of three typical catechins (epigallocatechin gallate (EGCG), epigallocatechin (EGC), and epicatechin (EC)) on the structure and functional properties of soy protein isolate (SPI) under alkali conditions were investigated. Compared with the native SPI, the fluorescence intensity of SPI–EC, SPI–EGC, and SPI–EGCG complexes decreased, while their fluorescence quenching rate and binding sites increased, indicating the formation of covalent complexes. The SPI–EGCG complex has a higher fluorescence quenching rate and more binding sites than those of SPI–EC and SPI–EGCG complexes. The emulsifying activity and stability of the SPI–EGCG complex were 1.16 m2/g and 147 min, respectively, higher than those of latter two complexes. Hence, the functional property of SPI and the stability of catechins could be improved by the covalent interaction between the two. This study provides new insights into the relationship between the type of polyphenol and the structure of SPI.

Effect of d-galactose on physicochemical and functional properties of soy protein isolate during Maillard reaction

Maillard reaction (MR) of soy protein isolate (SPI) and d-galactose with the mass ratio (4:1, 2:1, and 1:1) was conducted. The conformation of SPI was changed from ordered to disordered and the SPI molecule was unfolded and stretched after MR. The amino acids covalently bonded to the carbonyl group of d-galactose are mainly lysine and arginine of SPI. In addition, sodium dodecyl sulfate-polyacrylamide gel electrophoresis indicated the formation of constituents with high-molecular-weight during MR. The more the d-galactose content in MR, the higher the degree of glycation and surface hydrophobicity of SPI-d-galactose conjugates. The solubility at different pH, emulsifying and foaming properties of SPI were enhanced after MR, and these properties increased with the increasing of d-galactose content in MR. d-galactose enhanced the viscosity of SPI, and changed its viscoelasticity. Meanwhile, the hydrophilic d-galactose group improved the physiological and biological properties of amphiphilic SPI, the more d-galactose content in MR, the more significant the enhancement of the properties including the fat binding capacity, bile acid binding capacity, hypoglycemic effect, antioxidant and antibacterial activity. Our work showed that d-galactose had a great influence on the structure of SPI, and further affected its functionalities.

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.