Properties Of Soy Protein Isolate Research Articles

Effect of glycosylation modification on structure and properties of soy protein isolate: A review.

Soybean protein isolate (SPI) is a highly functional protein source used in various food applications, such as emulsion, gelatin, and food packaging. However, its commercial application may be limited due to its poor mechanical properties, barrier properties, and high water sensitivity. Studies have shown that modifying SPI through glycosylation can enhance its functional properties and biological activities, resulting in better application performance. This paper reviews the recent studies on glycosylation modification of SPI, including its quantification method, structural improvements, and enhancement of its functional properties, such as solubility, gelation, emulsifying, and foaming. The review also discusses how glycosylation affects the bioactivity of SPI, such as its antioxidant and antibacterial activity. This review aims to provide a reference for further research on glycosylation modification and lay a foundation for applying SPI in various fields.

Effect of transglutaminase crosslinking combined with lactic fermentation on the potential allergenicity and conformational structure of soy protein.

Food allergies are a growing concern worldwide, with soy proteins being important allergens that are widely used in various food products. This study investigated the potential of transglutaminase (TGase) and lactic acid bacteria (LAB) treatments to modify the allergenicity and structural properties of soy protein isolate (SPI), aiming to develop safer soy-based food products. Treatment with TGase, LAB or their combination significantly reduced the antibody reactivity of β-conglycinin and the immunoglobulin E (IgE) binding capacity of soy protein, indicating a decrease in allergenicity. TGase treatment led to the formation of high-molecular-weight aggregates, suggesting protein crosslinking, while LAB treatment resulted in partial protein hydrolysis. These structural changes were confirmed by Fourier transform infrared spectroscopy, which showed a decrease in β-sheet content and an increase in random coil and β-turn contents. In addition, changes in intrinsic fluorescence and ultraviolet spectroscopy were also observed. The alterations in protein interaction and the reduction in free sulfhydryl groups highlighted the extensive structural modifications induced by these treatments. The synergistic application of TGase and LAB treatments effectively reduced the allergenicity of SPI through significant structural modifications. This approach not only diminished antibody reactivity of β-conglycinin and IgE binding capacity of soy protein but also altered the protein's primary, secondary and tertiary structures, suggesting a comprehensive alteration of SPI's allergenic potential. These findings provide a promising strategy for mitigating food allergy concerns and lay the foundation for future research on food-processing techniques aimed at allergen reduction. © 2024 Society of Chemical Industry.

Chitosan mitigates the beany flavor and improves the functional properties of soy protein isolate via the electrostatic interaction

Soybean protein isolate, as the most representative plant-based protein, has severely limited the acceptance of consumers due to its beany flavor. Conventional physical or chemical methods to remove the beany flavor often impair the functional properties of SPI. The effect of different coacervation ratios and chitosan molecular weight with soy protein isolate (SPI) via coacervation on the functionalities and beany flavor were studied. Results showed that the low molecular weight CS (LC) was more effective in decreasing the beany-flavor and increasing the emulsifying stability and antioxidant capacity of SPI. Compared with the LC, high molecular weight CS significantly enhanced the emulsifying activity. Additionally, the complex ratio of 30:1 was more effective in improving functionalities and flavor attributes of SPI simultaneously. The results of hierarchical cluster analysis and principal component analysis indicated that the flavor compounds between SPI-CS coacervates and SPI could be well distinguished. Additionally, the representative beany-flavor compounds of SPI obviously alleviated after coacervated with the CS. The ζ-potential, particle size and FTIR result illustrated the complex coacervates of SPI-CS via electrostatic interaction and hydrogen bonds. The surface hydrophobicity result illustrated that the CS moderately modified the structure of SPI via coacervation. The secondary structure content showed that the α-helix and β-turn content of SPI-CS increased, and the β-sheet decreased remarkably. Additionally, LC was more easily coacervated with the SPI than that of medium/high molecular weight CS. This work may provide an effective methodological and theoretical basis for further improving the functionalities and flavor profile of plant-based protein.

Synergistic effect of gellan gum and guar gum on improving the foaming properties of soy protein isolate-based complexes: Interaction mechanism and interfacial behavior

Interactions among multi-component play a critical role in modulating the foaming properties of aerated foods. This study evaluated the mechanisms of synergistic improvement of gellan gum (GEG) and guar gum (GUG) on the foaming properties of soy protein isolate (SPI)-based complex. The results showed that the GEG/GUG ratio was closely related to the intermolecular interactions of SPI-based ternary complex and the dynamical changing of its foaming properties. The SPI/GEG/GUG ternary complex with a GEG/GUG ratio of 2/3 exhibited the highest foamability (195 %) and comparable foam stability (99.17 %), which were 32.95 % and 2.99 % higher than that of SPI/GEG binary complex. At this ratio, GUG promoted the interactions between SPI and GEG, and bound to complex's surface through hydrogen bonding, resulting in the increase of particle size and surface charge, and the decrease of surface hydrophobicity. Although this reduced the diffusion of complex onto the air/water interface, it increased permeation rate and molecular rearrangement behavior, which were the potential mechanisms to improve the foaming properties. Additionally, the synergistic effect of GEG and GUG also enhanced the elastic strength and solid characteristics of foam systems. This study provided a theoretical guidance for the targeted modulation of foaming properties of multi-component aerated foods.

Theanine improves the gelation of soy protein isolate by modifying protein conformation and enhancing molecular interaction

This study systematically investigated the dose-effect relationship and regulatory mechanism of theanine on the gelling properties of soy protein isolate (SPI). The results indicated that the strength and water holding capacity of 0.10% theanine-SPI gel increased by 238.80% and 1.13% compared with pure SPI gel, respectively. Hydrogen bonds and van der Waals forces mainly promoted the binding of theanine to β-conglycinin and glycinin. This binding could further change the protein aggregation state (reducing particle size and irregular aggregation), functional groups (exposing more hydrophilic amino acid residues and sulfhydryl groups), and molecular structure (α-helix and β-turn transforming into β-sheet). Furthermore, a more uniform and dense three-dimensional gel network was formed in the composite gels, offering the structural basis for improving the performance of the SPI gel. The results will provide theoretical basis and technical support for the precise regulation of gel properties of the functional amino acid-SPI complex as well as the efficient creation of new SPI-based foods.

Improving the textural and functional properties of soy protein isolate using dielectric barrier discharge (DBD) plasma-assisted pH-shifting

This study aimed to improve the textural and functional properties of soy protein isolate (SPI) through a plasma-assisted pH-shifting method to create an alternative to meat products. The SPI was treated with DBD plasma for 0, 5, 10, and 15 min and then subjected to pH-shifting of 10 and 12 for 48 h before being adjusted to a neutral pH. The changes in the secondary structure of protein were evaluated using FTIR spectroscopy, free sulfhydryl measurement, and scanning electron microscopy (SEM). Heating the pH-shifted suspensions resulted in the formation of SPI gels with a densely cross-linked polymer-like network. Rheological and textural properties indicated that the pH-shifting treatment of SPI led to the production of stiff gels, so that the gel hardness increased from ∼6.75 to ∼13.28 N after 15 min plasma treatment at pH 12-shifting. The DBD plasma pretreatment negatively affected the functional properties of the SPI and decreased the solubility about 12 and 8% after 10 min plasma treatment at pH-shifting 10 and 12, respectively. The plasma-assisted pH-shifting offered a new approach for preparing SPI gel with enhanced water holding capacity, potentially expanding the range of applications for SPI in food formulations that require gelling and texturizing functions.

Effect of hydrocavitation treatment on physicochemical and functional properties of soy protein isolate

A hydrocavitation reactor was employed to treat diluted samples of soy protein isolate (SPI) at room temperature for 0, 60, and 90-minute intervals, revealing significant improvements in vitro enzymatic digestion, trypsin inhibition, water holding, oil holding, emulsification, and solubility properties. The secondary protein structure underwent significant modifications, with an increase in surface area, etching phenomena, and structural aggregation. The extent of amino acid digestion for hydrocavitation-treated proteins exhibited an augmentation from 180.9 % ± 1.429 μg/mL to 189.5 % ± 0.556 μg/mL. Additionally, the water holding capacity of the treated proteins increased from 3.51 % ± 0.131 to 3.78 % ± 0.097, while there was a corresponding decrease in oil holding capacity. Solubility showed a noteworthy rise from 24.70 % ± 0.042 to 38.23 % ± 0.031 following the hydrocavitation treatment. These findings underscore the potential of hydrocavitation technology as an appealing avenue for non-thermal, chemical-free food processing, enhancing product quality and digestibility through minimal processing techniques.

Development of soy protein isolate-based orally disintegrating film: Improvement of disintegration speed, mechanical properties, and thermal stability by β-Cyclodextrin

The effect of β-Cyclodextrin (β-CD) at different concentrations (0–20% w/w) on the function and properties of soy protein isolate (SPI)-based orally disintegrating films (ODF) was studied. The results of moisture content and contact angle indicate that the inclusion of β-CD enhances the moisture content and surface hydrophilicity of ODF. The thickness ODF samples is between 0.031 and 0.041 mm. Due to the addition of β-CD, ODF disintegration rates increased by 47.86%–64.62%. Scanning electron microscope, and mechanical analysis show that ODF with a β-CD concentration of 10% w/w has the best performance, presenting the smoothest surface, maximum tensile strength (TS) and elongation at break (EB). FTIR spectrum results show that there are physical entanglements and hydrogen bonding interactions between SPI and β-CD, and appropriate concentrations of β-CD (5% w/w and 10% w/w) can transform random coils into β-sheets. Once the concentration exceeding 10% w/w, β-CD will crystallize and precipitate on the ODF surface, which weakens the mechanical properties of the ODF and the strength of the SPI network structure. Thermogravimetric test results show that β-CD improves ODF thermal stability. This research offers a significant theoretical foundation for the advancement of ODF that are protein-based and not hydrolyzed.

Soy protein isolate-catechin complexes conjugated by pre-heating treatment for enhancing emulsifying properties: Molecular structures and binding mechanisms

This study aimed to investigate the impact of different pre-heating temperatures (ranging from 40 °C to 80 °C) on the interactions between soy protein isolate (SPI) and catechin to effectively control catechin encapsulation efficiency and optimize the emulsifying properties of soy protein isolate. Results showed that optimal heat treatment at 70 °C improved catechin encapsulation efficiency up to 93.71 ± 0.14 %, along with the highest solubility, enhanced emulsification activity index and improved thermal stability of the protein. Multiple spectroscopic techniques revealed that increasing pretreatment temperature (from 40 °C to 70 °C) altered the secondary structures of SPI, resulting in a more stable unfolded structure for the composite system with a significant increase in α-helical structures and a decrease in random coil and β-sheet structures. Moreover, optimal heat treatment also leads to an augmentation of free sulfhydryl groups within complex as well as exposure of more internal chromophore amino acids on molecular surface. Size-exclusion high-performance liquid chromatography and SDS-PAGE analysis indicated that the band intensity of newly formed high-molecular-weight soluble macromolecules (>180 kDa) increased as the pre-heating temperature rose. Furthermore, fluorescence spectroscopy and molecular docking analysis suggest that hydrophobic and covalent interactions were involved in complex formation, which intensified with increasing temperature.

Development of Novel Nanocarriers by Ultrasound and Ethanol-Assisted Soy Protein Isolate: Enhancing the Resistance of Lutein to Environmental Stress.

The aim of this work was to investigate the effects of the processing sequence of ultrasound and ethanol on the physicochemical properties of soy protein isolate (SPI), which were further evaluated for the morphology and stability of SPI-lutein coassembled nanoparticles. The results showed that the sequence of ultrasound followed by ethanol treatment was the optimal one. The samples were subjected to ultrasonication followed by subunit disassembly and reassembly induced by 40% (v/v) ethanol, with the resulting molecular unfolding and subsequent aggregation being attributed to intramolecular hydrogen bonds. The recombined nanoparticles had smaller particle size (142.43 ± 2.91 nm) and turbidity (0.16 ± 0.01), and the exposure of more hydrophobic groups (H0 = 6221.00 ± 130.20) induced a shift of SPI structure toward a more ordered direction. The homogeneous and stable particle provided excellent stability for the loading of lutein. The bioaccessibility (from 25.48 ± 2.35 to 65.85 ± 1.78%) and release rate of lutein were modulated in gastrointestinal digestion experiments. Our discoveries provide a new perspective for the development of combined physicochemical modification of proteins as nanocarriers in functional foods.

Effects of high hydrostatic pressure on the functional properties of soy protein isolate

AbstractIn this study, functional properties of high hydrostatic pressure (HHP)‐treated soy protein isolate (SPI) samples including protein solubility, emulsification activity (EA), and water holding capacity (WHC) were studied. Fourier transform infrared spectroscopy (FTIR), viscosity, and nuclear magnetic resonance (NMR) relaxometry experiments were performed. Three pressure (300, 400, and 500 MPa), two pH (5.0 and 7.0), and two temperature levels (25 and 40°C) were used to prepare SPI samples. Solubility of SPI was more pH‐dependent than HHP‐dependent, whereas WHC was more sensitive to pressure. Samples processed at 300 MPa, pH 5.0, and 40°C demonstrated higher EA (p < .05) than the untreated samples. Pressure application significantly reduced the viscosity of SPI dispersions (p < .05). Samples processed at 300 MPa, pH 5.0, and 40°C and at 400 MPa, pH 5.0, and 40°C attained the longest transverse relaxation time (T2) values reflecting their low solubility profiles. Thus, results indicated that HHP was able to modify the functional properties of SPI at different temperature and pH conditions.Practical ApplicationsHigh hydrostatic pressure (HHP) is an emerging technology with its diverse range of applications in food industry. Modification of functional properties of food ingredients is one of the latest applications of HHP treatment. This study demonstrated that HHP treatment was able to modify some functional properties of soy protein isolate (SPI) samples including water holding capacity, solubility, and emulsification activity. Pressure level, pH, and temperature affected the functional properties of SPI samples. The parameter type/range and results of this study could be used in model HHP studies to improve some functional properties of SPI for different purposes.

Physicochemical and antimicrobial properties of soy protein isolate films incorporating high internal phase emulsion loaded with thymol

Oil-in-water (O/W) high internal phase (HIP) emulsion was prepared to investigate its effects on the physicochemical properties and antimicrobial properties of soy protein isolate (SPI)-based films. The particle size and migration degree of oil droplets in the SPI film-forming solution with HIP emulsion and the films were lower than those with conventional O/W emulsion or oil. The SPI-based emulsion films with HIP emulsion containing 30 % oil had the lowest water vapor permeability (1.15 × 10−10 g·m−1·s−1·Pa−1), glass transition temperature (40.93 °C) and tensile strength (4.47 MPa), and the highest transparency value (12.87) and elongation at break (160.83 %). The antimicrobial test of the SPI-based emulsion films loaded with thymol showed that the thymol encapsulation efficiency, sustained release effect, and growth inhibition effect on microbes were higher for the films with HIP emulsion than those for the films with O/W emulsion or oil.

Oil-water interfacial behavior of soy protein nanoparticles in high internal phase Pickering emulsion

We investigated the interfacial properties of soy protein isolate (SPI) heat aggregation nanoparticles (SPN) at the oil-water (O/W) interface, as well as the preparation and rheological properties of high internal phase Pickering emulsions (HIPPEs). Increasing the concentration of SPN led to a reduction in the dynamic interfacial tension (γ) and facilitated the diffusion and permeation processes. The interface became adsorbed by a multilayer protein film, reaching almost saturation, which hindered further rearrangement processes between SPNs. SPN formed a viscoelastic film at the O/W interface, with the interfacial viscoelastic modulus (E) proportional to the SPN concentration, resulting in thicker and stronger interface films. For SPN films with concentrations of 0.2–1.5 wt%, strain hardening was observed during compression and strain softening during extension under relatively large amplitudes (>20%). Conversely, films with concentrations of 2.0–3.0 wt% exhibited a linearly elastic response. Optical microscopy of SPN-stabilized HIPPEs and droplet surface cryo-scanning electron microscopy (cryo-SEM) indicated that increasing SPN concentration improved interface properties. Furthermore, rheological results on HIPPEs revealed that higher SPN concentrations enhanced viscoelasticity and emulsion recovery. These findings deepen our understanding of soy protein particle adsorption at the O/W interface and the rheological implications for HIPPEs applications.

Effect of combined enzyme and ultrasound treatment on the structure and gel properties of soy protein isolate: A comparative study of alkaline protease and pepsin

This study aimed to research the effects of enzyme and ultrasound combined modification on the structure and gel properties of soy protein isolate (SPI). Different modified protein samples were obtained by hydrolyzing soy isolate with alkaline protease and pepsin at 0%, 0.1%, 0.5%, and 1.0% of hydrolysis by ultrasound treatment (400 W, 20 min). The results showed that the SPI particle size, which modified by combined enzyme and ultrasound treatment (co-modified), was significantly lower (P < 0.05) and the particle size was more evenly distributed compared with those of the single modified samples. The best improvement in solubility and turbidity was observed for the co-modified SPI. The Fourier transform–infrared spectroscopy showed the most significant changes in the secondary structure content of the co-modified SPI. The protein structure was unfolded, and the contents of free sulfhydryl and H0 were improved. Additionally, the co-modified SPI gel had a uniform and compact gel network and higher water-holding capacity (WHC) and gel strength. After frozen storage, the combined enzyme and ultrasound treatment showed better frozen storage stability than single treatment: the WHC of the gel decreased slightly, the gel strength increased slowly, and the gel network was less damaged. In conclusion, combined enzyme and ultrasound treatment could be effective in improving the SPI structure and gel properties.

Effect of soluble dietary fiber on soy protein isolate emulsion gel properties, stability and delivery of vitamin D3

Emulsion gels with denser network microstructure and stronger mechanical properties have attracted increasing attentions for delivering lipophilic compounds. In this study, the effect of three distinct soluble dietary fiber (inulin (IN), resistant dextrin (RD) and stachyose (ST)) on the rheological, mechanical and microstructural properties of soy protein isolate (SPI) emulsion gel were firstly investigated. Compared with RD and IN, ST significantly accelerated water holding capacity and thermal stability, which exhibited more compact microstructure and more uniform emulsified oil droplets. Subsequently, the stability and bioavailability of vitamin D3 (VD3) in different delivery systems (medium chain triglycerides (MCT) embedding, SPI-ST emulsion embedding, SPI emulsion gel embedding and SPI-ST emulsion gel embedding) were continue evaluated. In vitro simulated digestion experiment demonstrated that the bioaccessibility of encapsulated VD3 in SPI-ST emulsion gel (69.95 %) was much higher than that of free embedding (48.99 %). In vivo pharmacokinetic experiment revealed that the bioavailability of VD3 was significantly enhanced in SPI-ST gel (p < 0.05), with the AUC0-24h value of 25-OH VD3 (the main circulating form of VD3) were 1.34-fold, 1.23-fold higher than that of free embedding, MCT embedding, respectively. These findings provide a possible approach for the development of high protein/fiber functional foods containing enhanced hydrophobic bioactives.

Improved physicochemical properties and in vitro digestion of walnut oil microcapsules with soy protein isolate and highly oxidized konjac glucomannan as wall materials

This study investigated the effect of the oxidation degrees of oxidized konjac glucomannan (OKGM) on the encapsulation efficiency (EE), physicochemical and in vitro digestive properties of soy protein isolate (SPI)-based microcapsules walnut oil using experimental and computational approaches. Microcapsules had the highest EE when the ratio of OKGM and SPI to oil was 2.5:1. With increasing the oxidation degree of OKGM, the EE of microcapsules was increased and the hygroscopicity was decreased. Molecular dynamics simulation results showed that SPI/oil/highly OKGM had relatively low binding energy (−4.03 × 106 kJ/mol) and strong electrostatic interactions, which may contribute to a higher EE and lower hygroscopicity of microcapsules, respectively. The oxidative stability of the oil was markedly improved by SPI and OKGM, and microcapsules prepared with SPI and highly OKGM had the highest in vitro digestion. This study provided theoretical support for broadening the application of microcapsules prepared with SPI and OKGM.

Enhancing the properties of soy protein isolate and dialdehyde starch films for food packaging applications through tannic acid crosslinking

The utilization of naturally derived biodegradable polymers, including proteins, polysaccharides, and polyphenols, holds significant promise in addressing environmental concerns and reducing reliance on nonrenewable resources. This study aimed to develop films with enhanced UV resistance and antibacterial capabilities by covalently cross-linking soy protein isolate (SPI) with dialdehyde starch (DAS) through the incorporation of tannic acid (TA). The covalent crosslinking of TA with DAS and SPI was shown to establish a stable chemical cross-linking network. The tensile strength of the resulting SPI/DAS/15TA film exhibited a remarkable increase of 208.27 % compared to SPI alone and 52.99 % compared to SPI/DAS film. Notably, the UV absorption range of SPI/DAS/10TA films extended from 200 nm to 389 nm. This augmentation can be attributed to the oxidation of TA's phenolic hydroxyl groups to quinone under alkaline conditions, which then facilitated cross-linking with the SPI chain via Michael addition and Schiff base reactions. Furthermore, the film demonstrated robust antibacterial properties due to the incorporation of TA. Collectively, the observed properties highlight the significant potential of the SPI/DAS/10TA film for applications in food packaging, where its enhanced mechanical strength, UV resistance, and antibacterial characteristics can contribute to improved product preservation and safety.

Investigation into the physiochemical properties of soy protein isolate and concentrate powders from different manufacturers

SummaryThe physiochemical properties of five commercially available soy protein isolates (SPI) from different manufacturers and one soy protein concentrate were analysed. Despite their identical botanical origin and an almost interchangeable molecular weight profile, remarkable differences were revealed in their solubility, protein dispersibility index (PDI), water holding capacity (WHC), zeta potential (measured at different pHs) and particle size distribution. Protein solubility and PDI values, which can be considered as a simple and reliable measure of soy protein powder's suitability for industrial formulations such as extrusion premixes, revealed to be strongly intercorrelated, with SPI A, B and E showing higher values at pH 7.0 and 9.0 as compared to their counterparts (sample C and D). WHC appeared to be less influenced by solubility, but greatly by particle size distribution. SPI A, B and E showed largest increase in diameter upon hydration (‘swelling’) and gave the highest WHC.

High moisture extrusion of soybean protein isolate: Effect of β-glucan on physicochemical properties of extrudates

This study is focused on exploring the effect of twin-screw high-moisture extrusion technology on the physico-chemical properties of β-glucan-soybean protein isolate (SPI-BG) extrudates. Different proportions (0 %, 1 %, 2 %, 3 %, 4 %, 5 %) of oat β-glucan (BG) were added with soybean protein isolate (SPI) to prepare SPI-BG extrudates. Results showed that the addition of a high quantity of β-glucan (BG) decreased the elastic properties of soy protein isolate (SPI) extrudates and then increased. The strengthening of S1-S2-S3 interactions (hydrogen bonds, hydrophobic interactions, and disulfide bonds) was primarily responsible for this trend. Fourier transform infrared (FTIR) spectral analysis was conducted which revealed that BG did not significant affect random coil content of SPI. However, it was observed that α-helix content was increased significantly and the β-sheet content was decreased. An observation was noted in the value of enthalpy (ΔH) change that increased from 115.80 J/g to 159.68 J/g.

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.