Protein Isolate Research Articles

Effect of ultrasonic treatment on the structure and emulsification properties of soybean isolate protein-hyaluronic acid complexes and the stability of their loaded astaxanthin emulsions

The purpose of this work was to prepare an astaxanthin emulsion stabilized by a soybean isolate protein (SPI)-hyaluronic acid (HA) complex and to investigate its protective effect on astaxanthin. In order to examine the impact of various ultrasonic energies (0 W–300 W) on the structural characteristics of the complex and the stability of the emulsion, the SPI-HA complex was created via ultrasonography. The findings demonstrated that ultrasonication may had an impact on the hydrophobic, electrostatic, and hydrogen bonding interactions between SPI and HA, which caused the protein structure to unfold and reveal the interior hydrophobic amino acid residues. Moreover, ultrasonication enhanced the emulsification qualities of SPI-HA complexes by lowering their average particle size. The rheological findings demonstrated that the emulsion's viscosity and energy storage modulus (G′) were considerably decreased by the ultrasonic treatment. The appearance of the emulsions and optical microscopy results further indicated that the emulsions prepared from SPI-HA had superior storage stability, pH stability, and light stability compared to pure SPI. SPI-HA exhibited superior emulsion stability and lower particle size at 150 W ultrasonic power. The AST incorporated in the emulsion was also well protected. The emulsion effectively slows down the degradation of AST. The findings of this study may help create more robust and natural emulsion delivery systems that guarantee the continuous or regulated release of lipophilic bioactive compounds.

Improve the fiber structure and texture properties of plant-based meat analogues by adjusting the ratio of soy protein isolate (SPI) to wheat gluten (WG)

The effects of the ratio change of SPI and WG (11: 1, 10: 2, 9: 3, 8: 4, 7: 5, 6: 6 and 5: 7) on the product characteristics of plant-based meat analogues (PBMAs) were investigated. The results show that the addition of WG significantly reduces the hardness and chewiness of PBMAs, but significantly improves the springiness and brightness of PBMAs. When the ratio of SPI to WG is 9: 3, PBMAs has the best fiber structure, storage modulus and apparent viscosity. Fourier transform infrared spectroscopy (FT-IR) results showed that the transition from α-helix to β-fold was an important reason for PBMAs fibers reinforcement. The intermolecular interaction of protein shows that the enhancement of fiber structure of PBMAs is related to the increase of disulfide bonds. In this study, low cost and high simulation degree PBMAs are provided as a reference for developing PBMAs.

Structure and functionality of Pleurotus geesteranus protein isolate as a function of pH.

Edible mushroom proteins hold great potential for food applications, but those extracted using the alkaline extraction-acid precipitation method typically exhibit poor solubility in neutral water, with the structural changes during acid precipitation remaining unclear. In this study, Pleurotus geesteranus protein isolate (PGPI) with high water solubility was prepared with alkaline extraction, followed by dialysis and freeze-drying, and the effects of pH on the structural and functional properties of PGPI were systematically investigated. PGPI was enriched in essential and aromatic amino acids, and the molecular weight of bands in the sodium dodecyl sulfate-polyacrylamide gel electrophoresis profile was mainly distributed below 45kDa. The zeta potential of PGPI changed from +16.84 to 17.58mV when the pH increased from 2 to 9, with a pI of 4.3. At pH 7, PGPI showed a size of 232.7nm. Away from pH 7, the particle size of PGPI increased. When the pH decreased from 7 to 2, PGPI exhibited a lower α-helix structure content and a higher β-sheet content and a gradual decrease in fluorescence intensity. In addition, as the pH approached 4, H0 and the content of SS group increased to a peak. These results indicated that lowering the pH induced the development of more ordered protein structure, which could be the primary reason for the poor water solubility of P. geesteranus protein obtained through alkaline extraction and acid precipitation. Additionally, these structural changes result in alterations to its functional properties, including water-holding capacity, oil-holding capacity, foaming capacity, foaming stability, emulsion activity index, and emulsion stability index.

Glycation of sunnhemp protein with dextran via dry heating: Thermal, micro-structural characterization, and amino acid profiling.

This study aims to obtain sunnhemp protein isolate (SHPI) and dextran conjugates by dry heating method of Maillard conjugation. The effects of different incubation time (0, 1, 3, 5, 7, and 9 days) on the molecular flexibility, available lysine content, antioxidant properties, molecular structure, and thermal and micro-structural properties of conjugates were compared with SHPI (no conjugation) at 60°C and 79% relative humidity. The results indicated the formation of SHPI-dextran conjugates as confirmed by the change in molecular flexibility, lysine content, antioxidant activities, color, and water activity values. The molecular structure revealed the confirmation of covalent bonding between SHPI and dextran. Differential scanning calorimetry and thermo-gravimetric analysis results exhibited improvement in the thermal stability of SHPI when conjugated with dextran. The microstructural characterization showed that Maillard conjugation changed the surface structure of SHPI. The analysis of amino acid composition displayed that lysine, arginine, and phenylalanine were the dominant Maillard reaction sites of SHPI and dextran. Among all the conjugated samples, 5 days of incubation time was selected as an optimum condition for the development of SHPI-dextran conjugates on the basis of the aforementioned characterization. Overall, it was concluded that Maillard conjugation of sunnhemp protein with dextran via dry-heating technique could modify and improve its various attributes. PRACTICAL APPLICATION: The conjugation of plant proteins with polysaccharide through the Maillard reaction under dry heating conditions represents a natural and green technique for improving the techno-functional properties of proteins. The study has the potential to establish framework for the utilization of Sunnhemp protein isolate-dextran conjugates. This approach offers the potential for cost-effective production of emulsifiers and development of effective encapsulating matrices. The investigation expands on an underutilized plant protein source facilitating an alternative to animal-based proteins and contributing to the development of a sustainable circular bioeconomy.

A multifunctional soybean protein isolates crosslinked gelatins composite mulch film: Fabrication, characterization, and application

The development of sustainable agriculture has boosted an increase in demand for biodegradable and multifunctional biomass-based mulch films. Herein, a sort of eco-friendly and multifunctional soybean protein isolates crosslinked gelatins (SPI-c-Gel) composite mulch films were elaborately designed through the Schiff base reaction. The formation of physical entanglement and chemical cross-linking between the molecular chains of SPI and Gel could effectively dissipate the loading energy and thereby strengthen the resistance of the composite mulch films to water penetration. Specifically, the maximum tensile strain and tensile stress were observed to increase from 4.05 MPa at 73.3 % for pure SPI film to 14.7 MPa at 151 % for optimized SPI-c-Gel0.3 mulch film. The swelling rate in water declined from 280 % for pure SPI film to 141 % for SPI-c-Gel0.3 composite film. Furthermore, the fabricated composite mulch film exhibited satisfied water retention, urea slow-release properties, and biodegradability. The application experiments of SPI-c-Gel0.3 composite mulch have shown that the seeds grew faster when cabbage seeds were covered by such mulch film during seed germination. Our findings provide a novel strategy for regulating the physical and chemical properties of biopolymer-based multifunctional mulch films, which may be employed to promote the development of sustainable agriculture.

Exploring the Nexus Between Emulsifier Characteristics and Salmonella Typhimurium Viability in Oil‐in‐Water Emulsions

ABSTRACTMolecular characteristics of emulsifiers such as their molecular weight (MW) and surface charge, not only affect the stability of the emulsion but also can have an impact on its capacity to either inhibit or promote microbial proliferation. These characteristics can affect the behavior of pathogens such as Salmonella Typhimurium in emulsion systems. The growth and thermal resistance of S. Typhimurium were monitored at different oil content levels (20%, 40%, and 60%) in emulsions stabilized by three whey protein‐based emulsifiers: whey protein isolate (WPI), whey protein hydrolysate (WPH), and a modified WPI with an alteration of charge (WPI+). Our study revealed that emulsifier itself with different MW and surface charge had no effect on bacterial growth and inactivation without oil inclusion (p > 0.05). However, it was found that higher bacterial growth rate at 60% oil content emulsion stabilized with WPI+ (0.65 ± 0.03 log CFU/h) than WPI (0.19 ± 0.04 log CFU/h), which showed the charge of emulsifiers has different effects on microbial dynamics in oil‐in‐water emulsion. Interestingly, WPI+ in emulsions also seemed to convey protection against thermal inactivation of bacteria. These data describe a complex interrelationship between the physicochemical characteristics of the emulsifier and its interacting nature with bacterial cells. They throw even more light on the insight about the importance of a strategic approach toward emulsifier selection in food formulations. This is crucial for the food safety and stability of products.

Wavelength selection enables robust quantification of oil content with near-infrared spectroscopy in pea protein gels produced under varying heating conditions

Thermal processing influences the near-infrared (NIR) spectra of food products, causing inaccuracy when quantifying the composition of the product. In this study, the effect of thermal processing on NIR measurements of the oil content in pea protein isolate (PPI) gels was investigated. Analysis of variance showed that the heating temperature (30°C–120 °C) during the production of PPI gels influenced large parts of the NIR spectra and time (2.5–15 min) only had a limited effect. Stepwise multiple linear regression was used to select a combination of 5 wavelengths that was suitable to create a robust model for the prediction of oil content (Q2 = 0.9928 ± 0.002, root mean standard error of prediction = 0.2806 ± 0.0423 wt%). This combination of wavelengths was shown to reduce the effect of the history of thermal processing on the measurement, improving the accuracy of oil content quantification. This approach can be applied for in-line quantification of the oil content of food products subjected to varying heating conditions using specialized sensors.

Isolation of ice structuring proteins from winter wheat in frigid region (Dongnongdongmai1) and the effect on freeze–thaw stability of dough

In this study, ice structuring proteins (WISPs) extracted from winter wheat in a frigid region were prepared and added to frozen-thawed dough. The WISPs were characterized, revealing that they contained a higher proportion of hydrophilic amino acids and had a molecular weight of approximately 15 kDa. The highest thermal hysteresis activity (THA) observed was 0.62 °C. The secondary structure of WISPs was determined to be as follows: β-sheet: 49.33 %, random coil: 13.87 %, α-helix: 16.35 %, β-turn: 20.45 %. The study investigated the effects of different additions of WISPs on the water mobility, glass transition temperature, microstructure, rheological properties, and texture analysis of frozen-thawed dough. The results demonstrated that the inclusion of WISPs reduced the fluidity of water and water migration in the dough during the frozen-thawed cycle. This protective effect preserved the internal structure and gluten network of the dough, leading to increased viscosity, elasticity, and improved texture properties of the frozen-thawed dough. Furthermore, the addition of WISPs at concentrations ranging from 0 % to 0.7 % resulted in a 1.8 °C increase in the glass transition temperature (Tg). Overall, these findings suggest that WISPs can serve as a beneficial additive for enhancing the freeze–thaw stability of dough.

Enhanced characterization and utilization of cowpea protein isolate: rheological and textural properties of heat-induced gels for plant-based egg omelet formulation

This study aimed to evaluate the potential of cowpea isolate (CPI) as an effective plant-based egg substitute by comparing its composition and physicochemical properties with those of commercial isolates, including mung bean, soy, and pea proteins. Sodium dodecyl sulfate–polyacrylamide gel electrophoresis identified a distinctive vicilin-like globulin in CPI that is critical for the unique functional properties of CPI. CPI has a smaller particle size, resulting in superior gelation capacity and water retention, which are essential for egg substitute applications. Thermal analysis revealed the high stability of CPI, which is advantageous for food processing. Notably, the unique heat-induced gelation behavior of CPI, characterized by a smooth transition from solid- to liquid-like states, provided a strength not observed in its commercial counterparts. Microstructural analysis showed that the CPI gel closely resembled the egg gel, underscoring the potential of CPI to mimic the texture of eggs, particularly in omelets.

Physicochemical, techno-functional, biochemical and structural characterization of a protein isolate from groundnut (Arachis hypogaea L.) paste treated with high-intensity ultrasound

The objective of this research was to evaluate the effect of ultrasound (HISound) (200, 400 and 600 W; 15–30 min) on the physicochemical, biochemical and structural techno-functional properties of a groundnut paste protein isolate (GPPI). HISound increased the contents of free sulfhydryls (552.22 %), total sulfhydryls (124.68 %) and α-helix (389.75 %), as well as molecular flexibility (50.91 %), hydrophobic surface (38.99 %), and particle size (171.45 %) of GPPI, which improved protein solubility by 8.05 %, oil holding capacity by 73.54 %, emulsifying stability index by 226.25 % and foaming capacity by 216.00 %, compared with non-sonicated GPPI. Also, the microstructure analysis revealed smooth structures, with molecular weights in the range of 13.88–67.07 kDa. Pearson analysis determined some highly significant correlations (r ≥ 0.90, p < 0.01) between some GPPI protein properties. The improvement of GPPI properties by HISound could contribute to its use as an ingredient for human consumption.

Antibacterial and wound healing stimulant nanofibrous dressing consisting of soluplus and soy protein isolate loaded with mupirocin

Severe cutaneous injuries may not heal spontaneously and may necessitate the use of supplementary therapeutic methods. Electrospun nanofibers possess high porosity and specific surface area, which provide the necessary microenvironment for wound healing. Here in, the nanofibers of Soluplus-soy protein isolate (Sol-SPI) containing mupirocin (Mp) were fabricated via electrospinning for wound treatment. The fabricated nanofibers exhibited water absorption capacities of about 300.83 ± 29.72% and water vapor permeability values of about 821.8 ± 49.12 g/m2 day. The Sol/SPI/Mp nanofibers showed an in vitro degradability of 33.73 ± 3.55% after 5 days. The ultimate tensile strength, elastic modulus, and elongation of the Sol/SPI/Mp nanofibers were measured as 3.61 ± 0.29 MPa, 39.15 ± 5.08 MPa, and 59.11 ± 1.94%, respectively. Additionally, 85.90 ± 6.02% of Mp loaded in the nanofibers was released in 5 days in vitro, and by applying the Mp-loaded nanofibers, 93.06 ± 5.40% and 90.40 ± 5.66% of S. aureus and E. coli bacteria were killed, respectively. Human keratinocyte cells (HaCat) demonstrated notable biocompatibility with the prepared nanofibers. Furthermore, compare to other groups, Sol-SPI-Mp nanofibers caused the fastest re-epithelialization and wound healing in a rat model. The findings of this study present a novel nanofiber-based wound dressing that accelerates the healing of severe skin wounds with the risk of infection.

Improving the emulsification characteristics of rapeseed protein isolate by ultrasonication assisted pH shift treatment

Rapeseed protein isolate (RPI) is an important nutrimental macronutrient in human diet due to its abundance in amino acids. However the poor emulsifying attributes of RPI limits its application in food industry, which needs to be overcome for its application in food industry. Ultrasonication-aided pH shift (UpHS) treatment is an efficient method for enhancing the functionality of plant/ food protein. In this work, the emulsification characteristics of RPI modified by UpHS technique under different solubility levels were studied. Results showed that the emulsifying activity and stability of modified RPI were significantly improved by 168.46 % (sample with high solubility treated by Ultrasonication-aided pH 12.5, HSpH 12.5) and 134.5 % (sample with high solubility treated by Ultrasonication-aided pH 1.5, HSpH 1.5), respectively compared with the native sample (P < 0.05), and the emulsifying activity was positively correlated (P < 0.05) with solubility. The emulsification stability under acidic condition was higher than that under alkaline condition (HSpH 12.5 increased by 83.5 %). In addition, the adsorption capacity and zeta potential of RPI were increased to 93.74 % and 13.83 % respectively, whereas the particle size and surface tension were reduced to 41.04 % and 23.63 % respectively. This indicates the changes in the molecular structure of modified rapeseed protein, which improved the emulsifying activity of RPI. Moreover, the interfacial film of emulsions formed by the modified protein had stronger compressive resistance, contributing to the enhanced emulsifying stability of the RPI. These results show that UpHS treatment can effectively improve the emulsification properties of proteins, and can be widely used in food industry.

The potential of protein-polysaccharide-based O/W and W/O emulsion gels strengthened by solid fat crystallization as realistic fat analogs

Herein, we develop novel O/W and W/O emulsion gels based on soybean protein isolate nanoparticles, xanthan gum, and crystalline fat to enhance 3D printability and achieve an effective alternative to butter. Palm mid fraction can self-assemble to form a fat crystal network, thus improving the structural strength of emulsion gels. Different emulsion gels are obtained by adjusting the sequence of crystallization and emulsification. The increased viscoelastic modulus of O/W emulsion gel is attributed to the tighter network structure between emulsion droplets. W/O emulsion gels exhibit better freeze-thaw stability due to the presence of fat crystal networks at the oil-water interface and the continuous phase. W/O emulsion gels with 60 wt% oil phase fractions had minimal print deformation rate. Both W/O and O/W emulsion gels significantly improve the hardness, gumminess, and chewiness of baked cakes. These findings provide new strategies for designing emulsion gels utilized in 3D printing and fat replacement.

Pecan (Carya illinoinensis (Wangenh.) K. Koch) nuts as an emerging source of protein: extraction, physicochemical and functional properties.

The increasing demand for sustainable alternatives to traditional protein sources, driven by population growth, underscores the importance of protein in a healthy diet. Pecan (Carya illinoinensis (Wangenh.) K. Koch) nuts are currently underutilized as plant-based proteins but hold great potential in the food industry. However, there is insufficient information available on pecan protein, particularly its protein fractions. This study aimed to explore the physicochemical and functional properties of protein isolate and the main protein fraction glutelin extracted from pecan nuts. The results revealed that glutelin (820.67 ± 69.42 g kg-1) had a higher crude protein content compared to the protein isolate (618.43 ± 27.35 g kg-1), while both proteins exhibited amino acid profiles sufficient for adult requirements. The isoelectric points of protein isolate and glutelin were determined to be pH 4.0 and pH 5.0, respectively. The denaturation temperature of the protein isolate (90.23 °C) was higher than that of glutelin (87.43 °C), indicating a more organized and stable conformation. This is further supported by the fact that the protein isolate had a more stable main secondary structure than glutelin. Both proteins demonstrated improved solubility, emulsifying, and foaming properties at pH levels deviating from their isoelectric points in U-shaped curves. Compared to the protein isolate, glutelin displayed superior water and oil absorption capacity along with enhanced gelling ability. The protein isolate and glutelin from pecan nuts exhibited improved stability and competitive functional properties, respectively. The appropriate utilization of these two proteins will support their potential as natural ingredients in various food systems. © 2024 Society of Chemical Industry.

Isolation and Purification of Protein from Ovis aries Placenta

Isolation and Purification of Protein from Ovis aries Placenta

Structural and functional properties of proteins isolated from four species of microalgae and their application in air-water interface stabilization

Herein, we extracted proteins from four microalgae: Chlamydomonas reinhardtii (CHR), Euglena gracilis (EUG), Spirulina platensis (SPP), and Spirulina maxima (SPM). Subsequently, their physicochemical and functional properties, as well as air-water interface adsorption behavior were investigated. Results demonstrated that the solubility and emulsifying properties of these proteins were significantly affected by pH, with minimum values observed near their isoelectric point (3.5) and maximum values at pH 11.0. Interestingly, the emulsifying properties of the four proteins were superior to soy protein isolate in the pH range of 3.0–7.0, indicating that these microalgae proteins may be suitable for applying as emulsifiers in foods. EUG exhibited the highest water/oil binding capacity, emulsifying activity, and emulsifying stability, which were attributed to its high surface hydrophobicity and β-sheet content, as well as small particle size. Dynamic adsorption behavior analysis illustrated that EUG showed faster diffusion and rearrangement rates, as well as a higher final equilibrated surface pressure value, contributing to its highest foaming capacity and foaming stability. This study greatly enhances the understanding of microalgae proteins and is expected to establish a theoretical foundation for developing novel protein resources that can be utilized in the foamed and emulsion-based food fabrication, including whipped cream and functional beverages.

Improving stability and bioavailability of ACNs based on Gellan gum-whey protein isolate nanocomplexes

Blueberry anthocyanins (ACNs) have been widely applied in the food industry and medicine due to their numerous beneficial properties. However, the stability of ACNs is extremely poor. This study aimed to develop a delivery system for ACNs using nanocomplexes prepared from gellan gum (GG) and whey protein isolate (WPI) via Maillard reaction. The effects of the GG-WPI nanocomplexes on the stability, antioxidant capacity, and bioavailability of ACNs were investigated. FTIR, fluorescence spectroscopy, and UV–vis absorption spectroscopy revealed covalent bonding between the GG and WPI in the nanocomplexes. The nanocomplex demonstrated a good loading efficiency for ACNs (60.34 %), with a particle size of 368.42 nm. It also showed better stability and bioaccessibility than free ACNs, and their DPPH radical scavenging capacity reached a maximum of 63.11 %. Our research is significant for developing novel multifunctional foods and constructing high-performance food delivery systems.

Evaluation of plant-based composite materials as 3D printed scaffolds for cell growth and proliferation in cultivated meat applications

This study aimed to evaluate plant-based 3D scaffolds for supporting the cultivation of animal cells for cultivated meat. The physical and chemical characteristics of pectin and composite gels (pectin + soy protein isolate [SPI] or pea protein isolate [PPI]) were analyzed. Rheological property analysis revealed that all materials exhibited viscoelastic solid behavior, shear thinning, and micro-structure recovery behavior, essential properties for 3D printing. Texture profile analysis (TPA) of composite gels demonstrated that some of the textural properties of these composite materials were in the range of mechanical properties of meat products including pork, poultry, and fish. The cytocompatibility and proliferative potential of these scaffold gels were evaluated using C2C12 (myoblast cells) as a model cell line, indicating their potential to support the growth of the animal cell without apparent toxicity. In examining 3D printability, incorporating protein into the pectin gel resulted in enhanced printability, characterized by reduced surface roughness and thinner thickness. Based on these analyses, a 3D printed scaffold was generated by using pectin, 30% SPI, and 10% PPI. Remarkably, the scaffolds with pectin and 10% PPI supported the growth of the cells, comparable to the cells grown on a tissue culture plate (positive control) demonstrating its potential to support animal cell growth. These findings highlight the promising potential of the formulated materials for applications within the cultivated meat industry.

Identification and comparison of N-glycome profiles from common dietary protein sources

The N-glycomes of bovine whey, egg white, pea, and soy protein isolates are described here. Glycoproteins from four protein isolates were analyzed by HILIC high performance liquid chromatography and quadrupole time-of-flight tandem mass spectrometry (HILIC-FLD-QTOF-MS/MS). A total of 33 N-glycans were identified from bovine whey and egg white, and 10 structures from soy and pea glycoproteins. The type of N-glycans per glycoprotein source were attributable to differences in biosynthetic glycosylation pathways. Animal glycoprotein sources favored a combination of complex and hybrid glycan configurations, while the plant proteins were dominated by oligomannosidic N-glycans. Bovine whey glycoprotein isolate contained the most diverse N-glycans by monosaccharide composition as well as structure, while plant sources such as pea and soy glycoprotein isolates contained an overlap of oligomannosidic N-glycans. The results suggest N-glycan structure and composition is dependent on the host organism which are driven by the differences in N-glycan biosynthetic pathways.

Microstructural and textual characteristics of blend gels and high-moisture meat analogs of soy protein isolate and faba bean protein concentrate

In this study, the effects of faba bean protein concentrate (FPC) and soy protein isolate (SPI) on the microstructure and texture of high-moisture meat analogs (HMMA) were extensively analyzed using rheological methodologies. Rheological analyses revealed that introducing FPC disrupted the gel structure and hindered the formation of a protein network among the SPIs. The gel stability also indicated that higher FPC content increased the susceptibility to continuous oscillation, potentially resulting in structural collapse. The β-sheets content decreased from 43.55 % to 37.19 % as the FPC content increased. The observed decline in the textural properties of HMMA, accompanied by microstructural alterations and diminished protein alignment, further supported the hypothesis that FPC disrupts protein network formation. Additionally, as the FPC content increased, the content of disulfide bonds decreased, emphasizing the role of FPC as a texture modulator that affects the rubbery texture of SPI.