Determination of the domain structure of the 7S and 11S globulins from soy proteins by XRD and FTIR

Enhancing structural and functional properties of commercially available pea protein isolate for plant-based meat analogues using combined pH-Shift, high-intensity ultrasound, and heat treatments

Diets based on pea protein have gained international recognition as a good substitute for meat or other main sources of protein. However, problems like gelling and emulsifying qualities make it difficult to use pea protein. To successfully overcome significant obstacles related to the use of pea protein in many industrial sectors, particularly meat, this study offers a combination of methods used to produce commercially accessible Pea Protein Isolate (PPI). High-intensity ultrasound (HIUS) at three magnitudes (2, 4, and 8 W/mL), heat at 60 °C, and pH at 10.0 were all integrated within the set. For artificial meat, PUHP2, PUHP4, and PUHP8 were the most promising of the nine treatments. After undergoing combined treatments (pH-shift, HIUS, and heat), favorable gelling was shown by treatments, emulsifying, and foaming properties while containing the ideal and desired protein size, as understood by the results in the gel electrophoresis. When treated PPIs were used to stabilize the sunflower oil-in-water emulsion, the emulsion capacity increased significantly for PUHP2, PUHP4, and PUHP8 (43.47 %, 46.57 %, and 40.90 % increase, respectively). Furthermore, solubility (for PUHP2, PUHP4, and PUHP8) had shown considerable (p < 0.05) improvement from 31.03 % ± 2.11 % (DPPI) to 53.33 % ± 2.3 %, 55.13 % ± 1.0 %, and 58.43 % ± 3.2 %, in SEM which accompanied by differences in the morphology of protein. This study's gelling properties (2.512 ± 0.1 N, 2.604 ± 0.1 N, and 2.168 ± 0.3 N, for PUHP2, PUHP4, and PUHP8) were crucial, primarily from the standpoint of plant-based meat analogs. The processes proposed by this study pea protein will be enabled that has undergone this series of chemical and physical processes to proceed in the direction of far better meat substitutes. Overall, this research contributes to the advancement of pea protein's use as an industrial protein and allows better usage of its hypoallergenic, non-GMO and high protein content.

Enhancing 3D food printing precision: Development and interaction behavior of soy protein isolate-konjac glucomannan-xanthan gum composite ink based on hot-melt extrusion

In the field of 3D printing, the physicochemical properties of composite inks are pivotal for constructing accurate printing networks. However, the precise fabrication of molded simulants using food 3D printing technology remains a challenging endeavor. The molecular structure and rheological properties of soybean protein isolate (SPI) make it prone to fracture under high shear stress, compromising printing accuracy and stability. This study aimed to address the deficiencies in precision and stability of existing soy protein-based inks for plant-based meats by developing a food composite ink system that incorporated SPI, konjac glucomannan (KGM), and xanthan gum (XG). The new ink system was designed to capitalize on the interactions between proteins and polysaccharides, as well as the synergistic effects of polysaccharides, to achieve high printing precision and the potential for simulant preparation. The addition of KGM and XG to the ink formulation enhanced the shear-thinning behavior, which was more amenable to the printing process, compared to the control group consisting of SPI alone. The SK1X1 composite ink demonstrated a significant improvement in printing precision by 40 % and in printing stability by 59 %, with final values reaching 99.11 % and 98.51 %, respectively. Additionally, hydrogen bonding was identified as a predominant factor in the gel network structure of SPI-KGM-XG composite inks. The self-assembling behavior of KGM-XG with SPI resulted in a robust spatial network structure, which in turn enhanced the thermal stability of the ink. In conclusion, the SPI-KGM-XG blends were determined to be suitable for use as thermo-extruded edible inks, and the synergistic effect of KGM-XG bolstered the gel properties of the hybrid inks, positioning them as ideal candidates for application in the 3D printing of meat simulants.

The mechanisms of inactivation of polyphenol oxidase in fresh-cut Agaricus bisporus by dual-frequency ultrasound combined with electrolytic water

Fresh-cut mushrooms are gaining popularity worldwide. However, their shelf life is limited because of enzymatic browning catalyzed by polyphenol oxidase (PPO), which leads to quality loss. The effects of different treatments (dual-frequency ultrasound (DFU), electrolytic water (EW), dual-frequency ultrasound combined with electrolytic water (DFU-EW)) on the molecular structure (Fourier infrared spectroscopy, X-ray diffraction, fluorescence spectroscopy, surface hydrophobicity, etc.), thermal properties, gene expression of PPO, and storage characteristics of mushrooms were investigated. The results showed that the DFU-EW decreased the relative contents of α-helix by 6.3 % and β-turns by 11.2 %, while increasing the contents of random coil and β-sheet by13.3 % and 4.7 %, respectively, compared to the control. The XRD analysis showed that the crystallinity of PPO was 7% higher than the control, while the fluorescence spectroscopy and surface hydrophobicity of PPO decreased from 921.7 (a.u) and 1154.5 to 393.5 (a.u) and 506.5, respectively. The DFU-EW treatment changed both the secondary and tertiary structures of PPO. The TGA analysis indicated that the thermal decomposition temperature decreased from the control 351.4 ℃ to 336.9 ℃. The gene expression level of AbPPO3 and AbPPO4 lowered. A 7-day storage period showed that DFU-EW inhibited the degree of browning, maintained the firmness of mushrooms, and stabilized the relative activity of PPO at 60% on average. Taken together, the DFU-EW treatment can effectively inactivate the PPO activity in fresh-cut mushrooms, thereby extending their shelf life, and this method provides a new insight to improve the quality of fresh-cut products.

Effect of magnetic induction electric field treatment of soybean protein isolate on their structural and interfacial properties

Induction electric field (IEF) technology is a new green treatment technology based on electric field, and its application has not been widely reported, especially in the direction of soybean protein isolate (SPI) modification. Therefore, IEF and several commonly used physical modification methods were used to investigate the effect on the structure and interfacial properties of SPI. The IEF treatment was found to be superior to the other groups in terms of emulsification performance, solubility and flexibility, which were enhanced by 44.61 %, 16.33 % and 30.55 %, as compared to untreated SPI. DSC shows more prominent thermal stabilisation of proteins after treatment. Secondary structure measurements revealed a decrease in α-helix content and an increase in random coil content, as well as an increase in surface hydrophobicity and free sulfhydryl groups, demonstrating a shift towards a loosely packed and disordered protein structure. At the same time, the IEF treatment particle size reaches a minimum and is uniformly distributed under the microscope, showing specific advantages in stabilising emulsions. In short, IEF provides a new way of thinking about protein modification, which is conducive to expanding the range of applications in the food industry.

Development and application of a polycationic soybean protein-based flocculant for enhanced flocculation and dewatering of dairy manure

In agricultural and waste management systems, dairy manure wastewater is often recycled for irrigation. However, a key challenge lies in handling suspended solids (SS) and effectively dewatering sludge. To address this, an innovative polycationic soybean protein-based flocculant (SPI+) was developed and applied to enhance flocculation and sludge dewatering efficiency. The polycationic protein chains of SPI+ were synthesized by grafting 2-(methacryloyloxy)ethyl trimethylammonium chloride (META) monomers onto soybean protein isolate (SPI) chains using an energy-efficient thiol-ene photografting method. This approach achieved a grafting ratio of 85%, endowing the SPI+ with a stable and strong positive zeta-potential (+30 mV) across a range of pH conditions. The SPI + exhibited exceptional flocculation performance, achieving a 96% flocculation efficiency, reducing sludge filtration resistance by 55%, and lowering filter cake moisture content by 10%. The SPI + flocculation and dewatering performance is comparable with synthetic-based commercial flocculant. This remarkable performance of SPI+ is attributed to its ability to effectively neutralize charges, form robust inter-particle bridges, and interact strongly with extracellular polymeric substances (EPS), particularly their protein components, within the sludge matrix. These properties significantly enhance both sludge aggregation and dewaterability. The underlying mechanisms of flocculation and dewatering were further elucidated using confocal imaging, surface morphology analysis of flocs, and quantification of EPS protein and polysaccharide content, providing valuable insights into its functional efficacy.

Unraveling distinct potential of pea (Pisum sativum L.) fractions (legumin, vicilin and albumin) by structural and functional characterization

Limited and unclear research exists on the individual capacity of major fractions of pea protein legumin (PL), vicilin (PV) and albumin (PA), which collectively contribute to the structural and functional properties of pea protein. Findings revealed that PV (72.26 ± 2.6 %) and PA (57.42 ± 4.1 %) displayed better solubility compared to PL. PL fraction possessed a complex three-dimensional structure, higher surface hydrophobicity (So), and superior oil-holding-capacity (OHC) contributing to its 4-fold strength (8.58 ± 0.5 N) and structured gel formation. The smaller particle size of PA was also accountable for the comparatively weaker gels and unstable emulsions compared to PL, while PV had the least emulsifying capacity, by non-uniform droplet distribution in CLSM served as proof. PL was found to be responsible for gelation, emulsification, and foaming in pea protein due to structural factors (relative abundance of α-helix and β-sheet). While, the flexible structure of PV, absence of cysteine residues, and disulfide bridges played a role in characteristics like foaming stability. Some protein in PV gel was found loose and did not appear to participate in gelation, hence forming a significantly weaker gel than PL. Despite relatively less So and complex structure, albumin (PA) had a smoother but weaker gel, more consistent and a smaller droplet size distribution in emulsions (compared to PV). Nonetheless, this study aims to fill a forgotten gap by providing baseline knowledge on the individual fractions of pea protein, defining their roles and paving the path for future research focusing on structural and functional properties of pea protein.

Pea-Protein-Stabilized Emulsion as a High-Performance Cryoprotectant in Frozen Dough: Effects on the Storage Stability and Baking Performance

The use of oil-in-water (O/W) emulsion has drawn increasing attention in the baking industry. Compared with some of the well-recognized functionalities, such as textural improvers and flavor carriers, its cryoprotective behavior in frozen dough has not been extensively investigated. Herein, this study reported a pea-protein (PP)-stabilized O/W emulsion with good freeze-thaw stability and evaluated its effectiveness as a high-performance dough cryoprotectant. Specifically, the emulsions were stabilized by 2, 3, and 4 wt% of PP (PP-2, -3, and -4, respectively) and incorporated into frozen doughs, whose cryoprotective effects were systematically evaluated in terms of dough storage stability and baking performance after 4 weeks of storage. Results showed that the frozen dough with PP-3 emulsion exhibited the most uniform water distribution and reduced content of freezable water as reflected by the results from differential scanning calorimetry and low-field nuclear magnetic resonance analyses. Moreover, the PP emulsion helped to maintain the integrity of the gluten network, thus enhancing the dough elasticity. Accordingly, the emulsion-added bread samples exhibited significantly improved loaf volume and textural properties (e.g., softness) and less baking loss. Our findings highlighted the potential of PP emulsion as a viable and high-performance dough cryoprotectant.

Effect of camellia oil body-based oleogels on the film-forming properties of soy protein isolate

Soybean protein isolate (SPI) was frequently used to make edible films due to its highly degradability and excellent film forming ability. However, the limited barrier properties and low tensile strength of SPI films prevent their application in food packaging. In this study, the SPI film was modified by blending camellia oil body-based oleogel (COBO). COBO improved the mechanical properties of SPI film and increased its light-blocking, water insolubility and barrier properties. Micrograph, particle size distribution, protein conformation and crystalline structure analysis illustrated that camellia saponin in COBO formed hydrogen bonds with SPI, significantly reduced the particle size of the film-forming emulsion, and enhanced the order and uniformity of composite films structure, thus improved the overall performance of the SPI films. The SPI-COBO film packing delayed the weight loss, total soluble solids content increase, and the decrease in hardness of stored strawberries. This study puts forwards a new approach for SPI film modification by blending natural emulsified lipids, contributing to the development of sustainable packaging alternatives.

Mild extraction of faba bean (Vicia faba L.) proteins against conventional methods: Impact on physicochemical and thermal characteristics

Faba bean (high- and low-tannin) protein isolates were water extracted followed by dialysis or micellization in comparison to concentrates from conventional alkali extraction + acid precipitation, and salt-based extraction (1% NaCl) + dialysis. Protein fractions were characterised for secondary structure conformational changes, crystalline structure, particle size distribution in aqueous suspension and thermal properties. Mild water or salt extraction did not influence particle size distribution. Based on XRD, FTIR and CD, β-sheet structures were the most abundant secondary structures and water extraction + dialysis had minimal impact on their native conformation. DSC results showed an association between protein purity, glass transition temperature and endothermic enthalpy. High melting temperature above glass transition confirms the suitability of faba bean proteins for thermal/extrusion processing. Fractionation method was a more significant determinant of physicochemical characteristics compared to the cultivar. Further exploration of the techno-functional characteristics of faba bean proteins is essential for value-added food applications.

Fabrication and characterization of novel electrospun nanofibers based on grass pea (Lathyrus sativus L.) protein isolate loaded with sumac (Rhus coriaria L.) extract

In this study, sumac extract was utilized as an active ingredient and combined with grass pea protein isolate and polyvinyl alcohol to produce novel active nanofiber mats using an electrospinning technique. First, nanofiber mats were fabricated by different ratios (100:0, 90:10, 70:30, 50:50, 30:70, 10:90, 0:100) of grass pea protein isolate and polyvinyl alcohol. The characterization of nanofiber mats revealed that the nanofibers with a polymer ratio of 50:50 had appropriate mechanical properties and presented a fibrous and uniform morphology. Therefore, the 50:50 polymer solution ratio was selected to produce active nanofibers by adding different amounts (0%, 2%, and 4% (w/v)) of sumac extract. The average diameters of nanofibers decreased from 150 ± 31 to 122 ± 25, and 105 ± 19 nm, by increasing the concentration of sumac extract. Based on the SEM results, the electrospun nanofibers exhibited a bead-free and smooth surface. The FTIR and XRD analyses indicated the presence of intermolecular hydrogen bonds between the components. The antioxidant activity of the nanofibers was confirmed by DPPH analysis and ranged between 3.33% and 68.75%. Additionally, the antimicrobial test results indicated that the nanofibers with the highest sumac concentration (4%) displayed inhibitory activity against Staphylococcus aureus, resulting in an inhibition zone of 10 mm. The optimal treatment of this study was grass pea protein isolate: polyvinyl alcohol ratio of 50:50 containing 4% sumac extract which can be used as a natural antimicrobial and antioxidant agent.

Optimization of ultrasound-assisted extraction of faba bean protein isolate: Structural, functional, and thermal properties. Part 2/2

Environmental concerns linked to animal-based protein production have intensified interest in sustainable alternatives, with a focus on underutilized plant proteins. Faba beans, primarily used for animal feed, offer a high-quality protein source with promising bioactive compounds for food applications. This study explores the efficacy of ultrasound-assisted extraction under optimal conditions (123 W power, 1:15 g/mL solute/solvent ratio, 41 min sonication, 623 mL total volume) to isolate faba bean protein (U-FBPI). The ultrasound-assisted method achieved a protein extraction yield of 19.75 % and a protein content of 92.87 %, outperforming the control method's yield of 16.41 % and protein content of 89.88 %. Electrophoretic analysis confirmed no significant changes in the primary structure of U-FBPI compared to the control. However, Fourier-transform infrared spectroscopy revealed modifications in the secondary structure due to ultrasound treatment. The U-FBPI demonstrated superior water and oil holding capacities compared to the control protein isolate, although its foaming capacity was reduced by ultrasound. Thermal analysis indicated minimal impact on the protein's thermal properties under the applied ultrasound conditions. This research highlights the potential of ultrasound-assisted extraction for improving the functional properties of faba bean protein isolates, presenting a viable approach for advancing plant-based food production and contributing to sustainable protein consumption.

Euglena gracilis Protein: Effects of Different Acidic and Alkaline Environments on Structural Characteristics and Functional Properties

Due to the growing demand for human-edible protein sources, microalgae are recognized as an economically viable alternative source of proteins. The investigation into the structural characteristics and functional properties of microalgin is highly significant for its potential application in the food industry as an alternative source of protein. In this research, we extracted protein from Euglena gracilis by using alkaline extraction and acid precipitation and investigated its structural characteristics and functional properties in different acidic and alkaline environments. The molecular weight distribution of Euglena gracilis protein (EGP), as revealed by the size exclusion chromatography results, ranges from 152 to 5.7 kDa. EGP was found to be rich in hydrophobic amino acids and essential amino acids. Fourier infrared analysis revealed that EGP exhibited higher α-helix structure content and lower β-sheet structure content in alkaline environments compared with acidic ones. EGP exhibited higher foaming properties, emulsifying activity index, solubility, free sulfhydryl, and total sulfhydryl in pH environments far from its isoelectric point, and lower fluorescence intensity (2325 A.U.), lower surface hydrophobicity, larger average particle size (25.13 µm), higher emulsifying stability index, and water-holding capacity in pH environments near its isoelectric point. In addition, X-ray diffraction (XRD) patterns indicated that different acidic and alkaline environments lead to reductions in the crystal size and crystallinity of EGP. EGP exhibited high denaturation temperature (Td; 99.32 °C) and high enthalpy (ΔH; 146.33 J/g) at pH 11.0, as shown by the differential scanning calorimetry (DSC) results. The findings from our studies on EGP in different acidic and alkaline environments provide a data basis for its potential commercial utilization as a food ingredient in products such as emulsions, gels, and foams.

Effect of Soybean Oil on the Improvement of the Functionality of Edible Membrane-Type Food Packaging Films Based on Caseinate-Carboxymethyl Chitosan Compositions

Edible film biopolymers are gaining attention to tackle problems of plastic waste and food safety to alleviate environmental problems associated with plastic products in food packaging. In this study, caseinate-carboxymethyl chitosan (CA-CMCH) composite films were made with the incorporation of soybean oil (SO) using a casting technique. The influence of different soybean oil concentrations at 0, 0.5, and 1% (w/w) on physical, mechanical, barrier, and surface characteristics of films composed of caseinate-carboxymethyl chitosan (CA-CMCH) was evaluated. The brightest film (L* value of 95.95 ± 0.30) was obtained with the edible film made from the control group of samples with sodium caseinate (NaCA-100; 100% NaCA). The results also indicated that samples with 1% SO in NaCA-75 and CaCA-75 had lower water vapor permeability (WVP), while those with NaCA-50 and CaCA-50 showed higher values of WVP. For mechanical properties, this study found that incorporating soybean oil into the caseinate-carboxymethyl (CA-CMCH) composite films led to an enhancement of both tensile strength and elongation at break. The morphological structures, determined using SEM, of control and composite films showed compact and homogenous surfaces. Overall, the addition of soybean oil contributed to the improvement of the functional properties of the edible films, offering potential solutions to the environmental issues associated with plastic packaging and enhancing the safety and performance of food packaging.

Effect of oil extraction methods on walnut oil quality characteristics and the functional properties of walnut protein isolate

Walnut oils were obtained by supercritical carbon dioxide extraction (SCB), cold-pressing (CP), hexane extraction (HE), and subcritical butane extraction (SBE), and walnut protein isolates (WPI) from the walnut cakes were performed. The results indicate that SCB has the highest oil yield for walnut oil, which was 62.72%, and the total content of trace nutrients (total tocopherols, total phytosterols, and total phenolic compounds) in SCB-walnut oil was also the highest at 2186.75 mg/kg, approximately 1.05 times higher than CP-walnut oil and 1.21 times higher than SBE-walnut oil. Meanwhile, the treatment of WPI with SCB results in a decrease in β-Sheet and α-Helix structures and an increase in β-Turn and Random coil structures. Thereby increasing its oil-holding capacity (OHC) and solubility by approximately 1.16 times and 1.27 times compared to CP, respectively. Interestingly, SCB as a green oil production technology, also has good prospects for retaining WPI functionality characteristics.

Pyrite-assisted degradation of methoxychlor by laccase immobilized on Fe3S4/earthworm-like mesoporous SiO2

Laccase immobilized and cross-linked on Fe3S4/earthworm-like mesoporous SiO2 (Fe3S4/EW-mSiO2) was used to degrade methoxychlor (MXC) in aqueous environments. The effects of various parameters on the degradation of MXC were determined using free and immobilized laccase. Immobilization improved the thermal stability and reuse of laccase significantly. Under the conditions of pH 4.5, temperature 40 °C, and reaction time 8 h, the degradation rate of MXC by immobilized laccase reached a maximum value of 40.99% and remained at 1/3 of the original after six cycles. The excellent degradation performance of Fe3S4/EW-mSiO2 was attributable to the pyrite (FeS2) impurity in Fe3S4, which could act as an electron donor in reductive dehalogenation. Sulfide groups and Fe2+ reduced the activation energy of the system resulting in pyrite-assisted degradation of MXC. The degradation mechanism of MXC in aqueous environments by laccase immobilized on Fe3S4/EW-mSiO2 was determined via mass spectroscopy of the degradation products. This study is a new attempt to use pyrite to support immobilized laccase degradation.

Evaluation of sono-physico-chemical and processing effects in the mixed sarcoplasmic protein/soy protein isolate system

Since it may be employed to guide the production of high-quality plant protein as a partial substitute for animal protein using sono-physico-chemical effects, it is important to investigate the mixing of animal and plant protein in ultrasound (UID)-assisted processing systems. A study group of sono-physico-chemical processing with five distinct soy protein isolate (SPI)/ sarcoplasmic protein (SPN) ratios was developed in this work. The results showed that adding additional SPN to the mixed protein can increase its sono-physico-chemical impact, and this effect is greatest when the ratio of SPI to SPN is 1:3. The high SPN group's grafting rate rose from 39.13% to 55.26% in comparison to the high SPI content group. Quercetin (Que) may more readily modify SPN than SPI in the "dual protein" system used in this work, highlighting the critical function of plant protein in controlling the effects of UID-assisted processing in the "dual protein" system. Changes in apparent viscosity and microstructure are the primary parameters that affect the severity of sono-physico-chemical effects in SPI/SPN mixed protein systems, in addition to structural variables.

Effect of Freezing on Soybean Protein Solution

To investigate the impact of frozen storage conditions on the physicochemical properties of soybean protein and explore the underlying mechanisms, this study focused on soybean isolate (SPI), ß-soybean companion globulin (7S), and soybean globulin (11S). The protein solutions were prepared at a concentration of 2% and subjected to freezing for 1 and 5 days. Subsequently, the protein content, physicochemical properties, secondary structure, sulfhydryl content, and chemical interaction forces were assessed and analyzed using UV spectrophotometry, Zeta potential measurements, SDS-PAGE, Fourier infrared spectroscopy, and endogenous fluorescence photoemission spectroscopy. The obtained results revealed that the solubility and total sulfhydryl content of SPI, 7S, and 11S exhibited a decreasing trend with prolonged freezing time. Among them, 11S demonstrated the largest decrease in solubility and total sulfhydryl content, followed by SPI, and 7S the least. During freezing, the aromatic amino acids of SPI, 7S, and 11S molecules were exposed, leading to increased hydrophobicity, protein aggregation, and particle size enlargement, and the structure of the protein changed from disordered structure to ordered structure. After freezing, the polarity of the microenvironment of SPI, 7S, and 11S increased, and their maximum fluorescence emission wavelengths were red-shifted. Notably, the largest red shift of SPI was from 332 nm to 335 nm. As freezing time increased, the contribution of hydrogen bonding increased, while the contribution of hydrophobic interactions decreased. This indicates that freezing affects the hydrophobic interactions, hydrogen bonding, and other chemical forces of the protein. The growth of ice crystals leads to the unfolding of protein molecular chains, exposure of internal hydrophobic groups, enhancement of hydrophobicity, and alters the secondary structure of the protein.

Lipid oxidation in foods and its implications on proteins

Lipids in foods are sensitive to various environmental conditions. Under light or high temperatures, free radicals could be formed due to lipid oxidation, leading to the formation of unstable food system. Proteins are sensitive to free radicals, which could cause protein oxidation and aggregation. Protein aggregation significantly affects protein physicochemical characteristics and biological functions, such as digestibility, foaming characteristics, and bioavailability, further reducing the edible and storage quality of food. This review provided an overview of lipid oxidation in foods; its implications on protein oxidation; and the assessment methods of lipid oxidation, protein oxidation, and protein aggregation. Protein functions before and after aggregation in foods were compared, and a discussion for future research on lipid or protein oxidation in foods was presented.

Preparation of egg white powder using electrohydrodynamic drying method and its effect on quality characteristics and functional properties

This research investigated the effects of spray drying (SD, set at 180 °C), freeze-drying (FD, set at -35 °C), and electrohydrodynamic drying (EHD) with and without the foam-mat method on egg white. The configuration used in EHD was a wire-to-plate type at room temperature. The results showed no significant difference in gel hardness and WHC% (P ≥ 0.05). Also, the foam-mat EHD powders resembled the FD powders in microstructure, appearance, flowability, and absorption intensity of the Amide I and II bands. Furthermore, the foam-mat EHD (DC-) powder had the highest protein content (66.1%), enthalpy (-183.06 J/g), and foaming capacity (725%) (P < 0.05). This finding was proved by FTIR, Raman, and SDS-PAGE tests, which revealed the minor structural changes in proteins (peptide chain structure, Amide I, Amide II, α-helix, and β-sheet). FD powder demonstrated good protein stability in zeta potential and foam stability tests.

Preparation and Characterization of Soybean Protein Adhesives Modified with an Environmental-Friendly Tannin-Based Resin

Soybean protein-based adhesives are limited in their application due to their poor wet bonding strength and poor water resistance. Herein, we prepared a novel, environmentally friendly soybean protein-based adhesive by adding tannin-based resin (TR) to improve the performance of water resistance and wet bonding strength. The active sites of TR reacted with the soybean protein and its functional groups and formed strong cross-linked network structures, which improved the cross-link density of the adhesives and then improved the water resistance. The residual rate increased to 81.06% when 20 wt%TR was added, and the water resistance bonding strength reached 1.07 MPa, which fully met the Chinese national requirements for plywood (Class II, ≥0.7 MPa). SEM observations were performed on the fracture surfaces of all modified SPI adhesives after curing. The modified adhesive has a denser and smooth cross-section. Based on the TG and DTG plots, the thermal stability performance of the TR-modified SPI adhesive was improved when TR was added. The total weight loss of the adhesive decreased from 65.13% to 58.87%. This study provides a method for preparing low-cost and high-performance, environmentally friendly adhesives.

Interaction and phase behavior of whey protein and propylene glycol alginate complex condensates

Whey protein (WP) is ubiquitously applied in food products, but its sensitivity to food processing conditions has limited its application. Herein, we chose propylene glycol alginate (PGA) to combine with WP to enhance its stability. The ideal ratio of WP/PGA for coacervation was 3:1, and the soluble complex and insoluble complex were formed at pH 5.2 (pHc) and pH 4.4 (pHφ1) at this ratio, respectively. The UV absorption spectra, fluorescence spectra, and XRD results revealed that the interaction between PGA and WP changed the tertiary conformation of WP. The FTIR and molecular docking results suggested electrostatic interactions, hydrogen bonding and hydrophobic interactions were all involved in the formation of WP-PGA complexes, and the thermal stability of WP was improved based on the DSC results. These findings supported PGA to keep dairy products stable and transparent at the isoelectric point and WP-PGA complexes could be applied in encapsulating bioactive substances.

Effect of sodium trimetaphosphate on the physicochemical properties of modified soy protein isolates and its lutein-loaded emulsion

Due to people's pursuit of healthy and green life, soy protein isolate (SPI) is occupying a larger and larger market share. However, the low solubility of SPI affects its development in the field of food and medicine. This paper aimed to investigate the effects of sodium trimetaphosphate (STMP) on the functional properties and structures of phosphorylated SPI and its lutein-loaded emulsion. After modification by STMP, the phosphorus content of phosphorylated SPI reached 1.2-3.61 mg/g. Infrared spectrum and X-ray photoelectron spectrum analysis confirmed that PO₄ ^3- had phosphorylation with -OH in serine of SPI molecule. X-ray diffraction analysis showed that phosphorylation destroyed the crystal structure of protein molecules. Zeta potential value of phosphorylated SPI decreased significantly. When STMP addition was 100 g/kg, particle size of protein solution decreased to 203 nm, and solubility increased to 73.5%. Furthermore, emulsifying activity and emulsifying stability increased by 0.51 times and 8 times, respectively. At the same protein concentration (1%-3% [w/w]), lutein-loaded emulsion prepared by phosphorylated SPI had higher absolute potential and smaller particle size. The phosphorylated protein emulsion at 2% concentration had the best emulsion stability after storage for 17 days. PRACTICAL APPLICATION: Phosphorylation significantly improved the emulsifying properties and solubility of SPI. Phosphorylated SPI significantly improved the stability of lutein-loaded emulsion. It provides theoretical basis for the application of phosphorylated SPI as emulsifier in delivery system and broadens the development of lutein in food and medicine field.

Providing New Insights on the Molecular Properties and Thermal Stability of Ovotransferrin and Lactoferrin

Ovotransferrin (OVT) is a multi-functional protein showing over 50% homology with Bovine lactoferrin (BLF) and human lactoferrin (HLF), which have the potential to be a substitute for lactoferrin (LF) due to the limited production of LF. To explore the substitutability of OVT, the molecular properties and thermal stability of OVT, BLF and HLF were characterized because these properties will affect the processing quality and biological activities of protein products when exposed to different processing conditions (e.g., temperature, pH, ion strength). The results showed that although obviously different isoelectric point (5.31, 9.12 and 8.75 for OVT, BLF and HLF, respectively), particle size distribution and hydrophobicity were found, they exhibited good dispersity because of high potential value. They showed an endothermic peak at 80.64 °C, 65.71 °C and 90.01 °C, respectively, and the denaturation temperature varied at different pH and ionic strength. OVT and BLF were more susceptible to heating at pH 5.0 as reflected by the decline of denaturation temperature (21.78 °C shift for OVT and 5.81 °C shift for BLF), while HLF could remain stable. Compared with BLF, OVT showed higher secondary structure stability at pH 7.0 and 9.0 with heating. For example, the α-helix content of OVT changed from 20.35% to 15.4% at pH 7.0 after heating, while that of BLF changed from 20.05% to 6.65%. The increase on fluorescence intensity and redshifts on the maximum wavelength after heating indicated the changes of tertiary structure of them. The turbidity measurements showed that the thermal aggregation degree of OVT was lower than BLF and HLF at pH 7.0 (30.98%, 59.53% and 35.66%, respectively) and pH 9.0 (4.83%, 12.80% and 39.87%, respectively). This work demonstrated the similar molecular properties and comparable thermal stability of OVT to BLF and HLF, which can offer a useful reference for the substitute of LF by OVT.

Formation, Structure and stability of high internal phase Pickering emulsions stabilized by BSPI-C3G covalent complexes

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The HIIPPE was stabilized by BSPI-C3G covalent particles.

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HIPPEs stabilized with 74% (v/v) oil phase fraction have a stable gel-like state.

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HIPPEs stability was the best with the 3 % (w/v) BSPI-C3G particle concentration.

Food-grade high internal phase Pickering emulsions (HIPPEs) are stabilized by protein-based particles, which have attracted extensive attention due to their good gel-like structure. The black soybean isolate protein/cyanidin-3-O-glucoside (BSPI-C3G) covalent particles were used as a particulate emulsifier to form stable HIPPEs with oil phase fractions (74 % v/v) and low particle concentrations (0.5 %–3 % w/v) The particle size distribution and microstructure demonstrated that the BSPI-C3G covalent particles acted as an interfacial layer and surrounded the oil droplets. As the concentration of BSPI-C3G particles increased from 0.5 % to 3 %, the droplet size, elasticity, antioxidant capacity of the heated or stored HIPPEs more stable. So, the HIPPEs had the best stability with the BSPI-C3G particle at 3 % (w/v) concentration. These findings may extend the application of BSPI and C3G in foods and provide the guidelines for the rational design of food-grade HIPPEs stabilized by protein/anthocyanin complexes.

Effect of Steam Explosion on Structural Characteristics of β-Conglycinin and Morphology, Chemical Compositions of Soybean Meal

In this study, steam explosion was applied as a means to degrade β-conglycinin. We investigated changes in morphology, the chemical composition of soybean meal, and the structural characteristics of β-conglycinin. The results showed that steam explosion at 0.7 MPa for 8 min could effectively decrease the β-conglycinin content of soybean meal while the histamine content was not increased. The structural characteristics of soybean meal proteins were analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), Fourier transform infrared spectroscopy (FTIR), circular dichroism (CD), and X-ray diffraction (XRD). Steam explosion caused the degradation of high weight proteins and reduced the band density of α', α, and β subunits in β-conglycinin. The micro-surface of soybean meal seemed to be in the cracked or puffed stage and the color became brown or dark after steam explosion. Steam explosion facilitated the dissolution of water-extractable arabinoxylans, which are 4.81 fold higher than that of native soybean meal. Phytic acid was exposed to the hydrothermal environment of the steam explosion process and consequently degraded by 12.95-24.69%. The 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activity of soybean meal extract was gradually increased from 20.70 to 33.71% with the rising of treated pressure from 0.3 to 0.7 MPa, which was 1.11-1.81 fold of native extract. The steam explosion may be a new modification technology that could decrease antigenicity, and steam-exploded soybean meal (0.7 MPa, 8 min) with lower β-conglycinin and phytic acid content that could be widely used in food products.

Green Synthesis of Soy Protein Nanocomposites: Effects of Cross-Linking and Clay Nanoparticles on the Mechanical Performance

A green synthesis scheme was adopted for preparation of soy-protein-based clay nanocomposites, in which soy protein isolates (SPIs) were utilized as the biodegradable resin and clay nanoparticles (CNPs) were used as the nanoreinforcing phase. Cross-linking of the SPIs was realized through an aqueous reaction scheme with oxidized sugars (e.g., glucose and sucrose as the typical constituents of soy flours) as the cross-linkers. Toughening effects of the cross-linkers, process parameters, and CNPs on the mechanical properties (e.g., tensile strength, stiffness, strain at break, and toughness) of the resulting SPI-based clay nanocomposites were examined by micromechanical tensile testing. The cross-linking and toughening mechanisms of the SPI-based nanocomposites were evaluated by Fourier transform infrared spectroscopy, sol-gel and color characterization, scanning differential calorimetry, and transmission electron microscopy. Thermal stability of the cross-linked SPIs was evaluated by thermogravimetric analysis. Experimental results show that cross-linking can noticeably improve both the tensile strength and tensile modulus of the resulting SPI films, and a small quantity of CNPs can obviously alter the mechanical properties of the resulting clay nanocomposite films. The present study indicates that defatted soy flours can be directly utilized for developing low-cost, SPI-based nanocomposites without the need for external plasticizers, and the entire synthesis is completely green without involvement of any petroleum-based organic solvents, polymers, and metallic catalysts. Such biodegradable SPI-based green nanocomposites have the potential to substitute fossil-based plastics and polymer composites for use in various industrial products and house utilities.

Functional and structural properties of soy 11S globulin: Influence of reverse micelle extraction

The effect of the reverse micelle extraction method (RMEM) on the physicochemical properties of soy 11S globulin was studied and compared with that of the traditional alkali solution-acid precipitation method (ASAPM). The results showed that the β-sheet structure content of soy 11S globulin obtained by RMEM was lower, while the β-turn structure content was higher compared with that obtained by ASAPM. Furthermore, the protein unfolding degree and surface hydrophobicity were lower than those observed using ASAPM. Therefore, RMEM better maintained the natural molecular structure of soy 11S globulin. The thermodynamic and rheological properties of soy 11S globulin obtained by these two methods were further compared, showing that the highest denaturation temperature and transition heat of soy 11S globulin extracted using ASAPM were different from those obtained using RMEM. Furthermore, soy 11S globulin extracted by RMEM showed stronger heat resistance and a higher denaturation temperature than that extracted by ASAPM. The final storage modulus and frequency sweep results showed that the gel formed by soy 11S globulin obtained using RMEM had high storage modulus and loss modulus. PRACTICAL APPLICATION: In this study, the effects of two different extraction methods on structural and functional properties of soy 11S globulin, such as thermodynamics and rheology, were investigated. We can know the 11S globulin extracted using the reverse micelle environment was more heat-resistant and heat-induced gel quality of 11S globulin was improved by the reverse micelle environment. These results will provide theoretical basis that would help determine the potential applications of soy 11S globulin in the food system.

Electrokinetic Enhancement of Water Flux and Ion Rejection through Graphene Oxide/Carbon Nanotube Membrane

Graphene oxide (GO) is promising for constructing next-generation high-performance membranes for water treatment and desalination. However, GO-based membranes are still subjected to low ion rejection or limited water flux. Herein, the electrokinetic effect is employed as a new strategy for the coenhancement of water flux and ion rejection through an ethylenediamine-polystyrenesulfonate intercalated graphene oxide/carbon nanotube (GO&EDA-PSS/CNT) asymmetric membrane. Benefiting from the external voltage applied across the GO&EDA-PSS layer, the electrokinetically driven water transport velocity is significantly increased from 0 to 23.7 μm s^-1 with increasing the voltage from 0 to 3.0 V. As a result, the water flux is improved from 9.1 to 17.4 L m^-2 h^-1 under a transmembrane pressure of 1 bar. Simultaneously, the rejection rate for NaCl is increased from 52.4% to 78.3%. Numerical analysis reveals that the increased rejection rate is attributed to the electrokinetic enhancements of water transport through the membrane and ion partitioning between the membrane and bulk solution. These results indicate that the assistance of the electrokinetic effect is an effective means to improve membrane filtration performance, which provides a new perspective on the design of advanced membranes for achieving high water flux and rejection efficiency.

Multicopper oxidase laccases with distinguished spectral properties: A new outlook

Multicopper oxidases (MCOs) has a unique feature of having the presence of four Cu atoms arranged into three (Type I, II and III) spectral classification. MCOs laccase due to its broad range of substrate specificity has numerous biotechnological applications. The two types of laccases include the typical blue and the atypical white, yellow laccases which have been isolated from diverse geographical locations globally. In the present study laccases were identified using Liquid Chromatograph Mass Spectrometer Studies (LCMS) study where blue laccase exhibited homology with Trametes villosa Q99044 and Q99046 and white, yellow laccase exhibited homology with Myrothecium verrucaria OX = 1859699; Q12737 and Trametes versicolor Q12717 respectively. The spectral comparison between laccases were determined via spectroscopic analysis where UV-spectra of blue laccase from Trametes versicolor had a peak at 605 nm (Type I Cu atom) whereas in case of white and yellow laccases the peak was absent and in addition had an absorption peak at 400nm. It was followed by X-Ray Diffraction (XRD) analysis of proteins where α-helix (10°) and β-sheet (22°) structure were observed in case of all the three laccases. However, the intensity of α-helix in white and yellow laccase was stronger as compared to the blue laccase whereas the intensity of β-sheet was stronger in case of blue laccase as compared to other two laccases. Further, Fourier-transform infrared spectroscopy (FTIR) analysis was performed which enabled the analysis of proteins where α-helix (1650–1658 cm⁻¹), β-sheets (1620–1640 cm⁻¹), amide I (1700−1600 cm⁻¹) amide II (bands at under 1400 cm⁻¹) and amide A, B (bands above 3000 cm⁻¹).

Functional and conformational properties of proteolytic enzyme-modified potato protein isolate

BACKGROUND

Potato protein hydrolysates (PPHs) were preparedwith Alcalase on intact potato protein isolates (PPI), with differenthydrolysis times (0.5-4 h), and functional and conformational properties of resultant hydrolysates were investigated.

RESULTS

The degree of hydrolysis changed during incubation. Peptide bond cleavage increased and hydrolysis progressed rapidly. Gel electrophoresis showed that, by increasing the hydrolysis time, peptides with an apparent molecular weight below 20 kDa increased. It also revealed that, among potato protein components, patatin was more sensitive to Alcalase® hydrolysis than protease inhibitors. Enzymatic hydrolysis significantly enhanced the solubility and foam capacity of PPHs, but impaired foam stability (P < 0.05). Limited enzymatic hydrolysates (0.5PPH) at the interface improved the emulsion activity and stability index. These emulsions also had the smallest z-average and polydispersity index and showed the highest zeta potential. Fourier-transform infrared spectrometry (FTIR) analysis indicated extensive disruption of hydrogen bonds in PPHs, besides augmentation of α-helices and β-turns, and a decline in the β-sheets in the secondary structure of the PPHs was shown.

CONCLUSION

Potato protein isolate, especially 0.5PPH, has good functional and conformational properties. Overall, our results provide new insights into the use of potato protein hydrolysates as a functional food component in the food industry. © 2019 Society of Chemical Industry.

Construction of Polymer Electrolyte Based on Soybean Protein Isolate and Hydroxyethyl Cellulose for a Flexible Solid-State Supercapacitor

Supercapacitors are a very active research topic. However, liquid electrolytes present several drawbacks on security and packaging. Herein, a gel polymer electrolyte was prepared based on crosslinked renewable and environmentally friendly soybean protein isolate (SPI) and hydroxyethyl cellulose (HEC) with 1.0 mol L⁻¹ Li₂SO₄. Highly hydrophilic SPI and HEC guaranteed a high ionic conductivity of 8.40 × 10⁻³ S cm⁻¹. The fabricated solid-state supercapacitor with prepared gel polymer electrolyte exhibited a good electrochemical performance, that is, a high single electrode gravimetric capacitance of 91.79 F g⁻¹ and an energy density of 7.17 W h kg⁻¹ at a current density of 5.0 A g⁻¹. The fabricated supercapacitor exhibited a flexible performance under bending condition superior to liquid supercapacitor and similar electrochemical performance at various bending angles. In addition, it was proved by an almost 100% cycling retention and a coulombic efficiency over 5000 charge–discharge cycles. For comparison, supercapacitors assembled with commercial aqueous PP/PE separator, pure SPI membrane, and crosslinked SPI membrane were also characterized. The obtained gel polymer electrolyte based on crosslinked SPI and HEC may be useful for the design of advanced polymer electrolytes for energy devices.

Self-assembly of plant protein fibrils interacting with superparamagnetic iron oxide nanoparticles

In situ fibrillation of plant proteins in presence of the superparamagnetic iron oxide nanoparticles (NP) promoted formation of a hybrid nanocomposite. The morphology of NP-fibril composite was revealed using ex-situ atomic force microscopy (AFM) in air. The NP-fibrils were associated into extended multi-fibril structures, indicating that the addition of NPs promoted protein association via β-sheet assembly. Real-time movement of NPs attached to fibrils under an external magnetic field was visualized using in-situ AFM in liquid, revealing that composite structures were stable at low pH, and displaying dipolar property of the NPs in the composite at high pH. Changes in magnetic properties of NPs when interacting with protein fibrils were quantitatively mapped using magnetic force microscopy (MFM). The magnetic moment of the NPs in composite was increased by co-existing with protein at low pH, while their dipolar nature was maintained at high pH. Self-assembly of the protein into fibrils is accelerated with increasing NP concentration within an optimal range, which is attributed to a fibrillation-competent conformation of the peptides. The latter was explained by the formation of favorable hydrogen bonds, electrostatic interactions, and efficient surface energy transfer between NPs and proteins.

A Crosslinked Soybean Protein Isolate Gel Polymer Electrolyte Based on Neutral Aqueous Electrolyte for a High-Energy-Density Supercapacitor

A crosslinked membrane based on renewable, degradable and environmentally friendly soybean protein isolate was formed by solution casting method. A series of gel polymer electrolytes were prepared with the crosslinked membranes saturated with 1 mol·L⁻¹ Li₂SO₄. The solid-state electric double-layer capacitors were fabricated with the prepared gel polymer electrolytes and activated carbon electrodes. The optimized solid-state supercapacitor delivered a single electrode specific capacitance of 115.17 F·g⁻¹ at a current density of 1.0 A·g⁻¹, which was higher than the supercapacitor assembled with the commercial separator in 1 mol·L⁻¹ Li₂SO₄. The solid-state supercapacitor exhibited an outstanding cycling stability, indicating that the gel polymer electrolyte based on the crosslinked soybean protein isolate membrane could be a promising separator for a solid-state supercapacitor.