Effect of ionic strength and mixing ratio on complex coacervation of soy protein isolate/Flammulina velutipes polysaccharide

Soy protein isolate(SPI)is a commercial protein with balanced amino acids,while the poor solubility impedes its use in traditional foods.To overcome the problem,the complex coacervation of SPI/Flammulina velutipes polysaccharide(FVP)were investigated.Initial results revealed that the suitable amounts of FVP contributed to reducing the turbidity of SPI solution.Under electrostatic interaction,the formation of SPI/FVP coacervates were spontaneous and went through a nucleation and growth process.Low salt concentration(C_(NaCl)=10,50 mmol/L)led to an increase in the critical pH values(pHc,pHφ1)while the critical pH values decreased when C_(NaCl)≥100 mmol/L.The concentration of NaCl ions increased the content ofα-helix.With the increase of FVP,the critical pH values decreased and the content ofβ-sheet increased through electrostatic interaction.At SPI/FVP ratio of 10:1 and 15:1,the complex coacervation of SPI/FVP were saturated,and the coacervates had the same storage modulus value.SPI/FVP coacervates exhibited solid-like properties and presented the strongest storage modulus at C_(NaCl)=50 mmol/L.The optimal pH,SPI/FVP ratio and NaCl concentration of complex coacervation were collected,and the coacervates demonstrated a valuable application potential to protect and deliver bioactives and food ingredients.

Drying kinetics of soy protein isolate-corn starch film during preparation and its moisture adsorption characteristics during storage

To better understand the mass transfer process of moisture in the soy protein isolate-corn starch(SPI-CS)films during preparation and storage process,the drying kinetics model of SPI-CS films with different formation conditions during the drying process and the moisture adsorption characteristics of the SPI-CS films under different humidity conditions were investigated.Within the range of experimental conditions,the moisture migration rule in the SPI-CS films during the drying preparation was combined with the Page model which was expressed as MR=exp(-kt^(n)).It was found that the adsorption equilibrium needed shorter time(about 3 h)when the SPI-CS films existed in the environment with lower humidity(RH<54%).Additionally,the secondorder adsorption kinetic equation was successful to describe the moisture adsorption characteristic of the SPICS films during storage under different humidity conditions.

Soy Protein Isolate Non-Isocyanates Polyurethanes(NIPU)Wood Adhesives

Soy-protein isolate(SPI)was used to prepare non-isocyanate polyurethane(NIPU)thermosetting adhesives for wood panels by reacting it with dimethyl carbonate(DMC)and hexamethylene diamine.Both linear as well as branched oligomers were obtained and identified,indicating how such oligomer structures could further cross-link to form a hardened network.Unusual structures were observed,namely carbamic acid-derived urethane linkages coupled with lactam structures.The curing of the adhesive was followed by thermomechanical analysis(TMA).It appeared to follow a two stages process:First,at a lower temperature(maximum 130℃),the growth of linear oligomers occurred,finally forming a physically entangled network.This appeared to collapse and disentangle,causing a decrease of MOE,as the temperature increases.This appears to be due to the ever more marked Brownian movements of the linear oligomer chains with the increase of the temperature.Second,chemical cross-linking of the chains appeared to ensue,forming a hardened network.This was shown by the thermomechanical analysis(TMA)showing two distinct MOE maxima peaks,one around 130℃ and the other around 220℃,with a very marked MOE decrease between the two.Plywood panels were prepared and bonded with the SPI-NIPU wood adhesive and the results obtained are presented.The adhesive appeared to pass comfortably the requirements for dry strength of relevant standards,showing to be suitable for interior grade plywood panels.It did not pass the requirements for wet tests.However,addition of 15%of glycerol diglycidyl ether improved the wet tests results but still not enough to satisfy the standards requirements.

Soy Protein Isolate Film by Incorporating Mandelic Acid as Well as Through Fermentation Mediated by Bacillus Subtilis

Soy protein isolate(SPI)biopolymeric films were prepared by adding different contents of mandelic acid(1 to 5%wrt SPI)to glycerol plasticized SPI by solution casting method.Also,SPI was fermented by Bacillus subtilis to get fermented SPI films by solution casting.Molecular mass determination of mandelic acid incorporated and fermented SPI films was carried out by sodium dodecyl sulphate-polyacrylamide gel electrophoresis(SDS-PAGE).Mandelic acid incorporated and fermented SPI films were characterized by Fourier-transform infrared spectroscopy(FT-IR),dynamic mechanical analysis(DMA),tensile strength,water uptake and optical transmittance studies.Results indicated that incorporation of mandelic acid in SPI resulted in high tensile strength(8.03 MPa)and highα-relaxation(Tα)as well as low water uptake.On the other hand,films cannot be prepared from fermented SPI with SPI contents of 8%and 12%.However,film from fermented SPI with 16%SPI content could be prepared but it exhibited low tensile strength(3.18 MPa)and low Tαas well as high water uptake.The resulting mandelic acid incorporated SPI films were also subjected to antimicrobial studies.At all the concentration of mandelic acid,we can easily observe the antimicrobial effect in mandelic acid incorporated SPI films unlike fermented SPI films.This work will be helpful in fabricating antimicrobial SPI film from renewable resources.

PREPARATION AND CHARACTERIZATION OF SOY PROTEIN ISOLATE(SPI)/MONTMORILLONITE(MMT) BIONANOCOMPOSITES

The bionanocomposites of soy protein isolate(SPI)/montmorillonite(MMT) have been prepared successfully via simple melt mixing,in which MMT was used as nanofiller and glycerol was used as plasticizer.Their structures and properties were characterized with X-ray diffraction(XRD),differential scanning calorimetry(DSC),scanning electron microscopy(SEM),thermogravimetric analysis and tensile testing.XRD、TEM and SEM results indicated that the MMT layers could be easily intercalated by the SPI matrix even by simpl...

ZnSe Nanoparticles Reinforced Biopolymeric Soy Protein Isolate Film

ZnSe nanoparticles have been synthesized by microwave assisted method by using zinc chloride,selenium powder and ethylene diamine.The synthesized nanoparticles have been characterized structurally by FT-IR and XRD as well as morphological characterization was done by scanning electron microscope(SEM).The crystallite size after synthesis was obtained around 30 nm for pure ZnSe nanocrystallites.However,from SEM micrograph,agglomerated ZnSe nanoparticles of irregular shapes were observed.The as-synthesized ZnSe nanoparticles at different contents(1 to 5%w/w w.r.t SPI)were incorporated into soy protein isolate(SPI)to produce reinforced SPI films by solution casting method.The ZnSe nanoparticles incorporated SPI suspensions were subjected to molecular mass and specific conductivity studies.Neat and ZnSe nanoparticles incorporated SPI films were structurally and mechanically characterized by FT-IR and tensile properties,respectively.Transmittance and water uptake studies were also carried out for ZnSe nanoparticles incorporated SPI films.The tensile strength and modulus increased from 5.80 MPa to 10.06 MPa and 18.84 MPa to 94.70 MPa with the increase in the contents of ZnSe nanoparticles from 0 to 5%.Moreover,the results also revealed a good antibacterial effect in ZnSe nanoparticles incorporated SPI film.The main application of nanoparticles incorporated SPI film will be in the area of biodegradable packaging.

Completely Green Synthesis of Ag Nanoparticles Stabilized by Soy Protein Isolate under UV Irradiation

A completely green pathway for the preparation of Ag nanoparticles was proposed, by using soy protein isolate （SPI） as stabilizer under UV irradiation and H2O as the environmentally benign solvent throughout the preparation. Transmission electronic microscopy （TEM） and zeta potential characterization results indicated that the Ag nanoparticles were stable and well dispersed with an average diameter about 13 nm, and X-ray diffraction （XRD） analysis of SPI/Ag composite nanoparticles confirmed the formation of metallic silver. UV-Vis spectrum showed that the Ag nanoparticles dispersion solution had the maximum absorbance at about 430 nm due to surface plasmon resonance of the Ag nanoparticles. Infrared spectroscopy confirmed that the polypeptide backbone of SPI was not cleaved during the conjugation process and that some active amino groups were oxidized. The SPI/Ag composite nanoparticles have excellent antibacterial activity against two representative bacteria, staphylococcus aureus （Gram positive） and escherichia coli （Gram negative） in the presence of SPI.

Study on the Hydrogen Bond Interaction Between Soy Protein Isolate and Glycerol Using Two-Dimensional Correlation Fourier-Transform Infrared Spectroscopy

A series of soy protein isolate(SPI)films plasticized by glycerol(Gly)were studied using attenuated total reflectance-Fourier transform infrared spectroscopy(ATR/FTIR).Perturbation-correlation movingwindow two-dimensional(PCMW2D)and two-dimensional correlation(2DCOS)analyses were applied to the amideⅠband and thus the hydrogen bond interaction between SPI and Gly was systematically investigated.When Gly concentrations were in the range 0~35%,the hydrogen bond amongβ-sheets was replaced by the one between SPI chain and Gly molecule,which caused these protein chains being changed toα-helix.However,the transformation ofβ-sheet toα-helix was saturated and both of them tend to change to random coil when Gly concentrations were in the range 35%~60%.

Influence of soy protein isolate on the gel properties of walnut protein isolate-κ-carrageenan treated with NaCl

The demand for plant protein is increasing significantly due to the shortage of protein resources.Walnut protein,the main by-product of preparing walnut oil,has limited application in the food industry due to its poor solubility.It was found that the soy protein isolate(SPI)concentration had significant effects on the gel properties of the walnut protein isolate(WNPI)-κ-Carrageenan(KC)composite system treated with 15 mmol/L NaCl.The results showed that the gel strength of the composite system increased first and then decreased with the increased concentration of SPI from 0 to 2.5%.The best rheological properties,texture properties,water holding capacity((92.03±1.05)%),swelling ratio((2.04±0.19)%),freeze-thaw stability and thermal stability(85.53°C)of the composite gel were found at an SPI concentration of 1%.In the meantime,the secondary structure of protein had the least α-helix content of 10.17% and the highest β-sheet content of 39.64%,the fluorescence intensity and free sulfhydryl content reached the highest value.1% SPI could also act as a filler for WNPI to enhance the intermolecular forces such as hydrophobic interaction between the two substances,thus forming a stable gel network structure.This study can provide technical support for improving the gel properties of walnut protein and producing new plant protein gel products.

Effects of xanthan gum on the rheological properties of soy protein dispersion

This study focused on the effects of addition of xanthan gum(XG)on the rheological properties of soy protein isolate(SPI)solution.Three types of tests(steady shear test,strain sweep test,and frequency sweep test)were performed to figure out the influences of shear rate on the viscosity of the SPI-XG hybrid system,the effects of strain variable on the storage modulus of the hybrid system,and the effects of frequency on both the storage modulus and the loss modulus of the hybrid system,respectively.SPI-XG hybrid system showed more obvious shear-thinning properties compared to pure SPI and pure XG solution.Meanwhile,it was found that the critical point of hybrid system was highly related to the XG concentration.XG can postpone the critical point strain amplitude to a higher value,and the addition of XG can enhance the strain resistance of hybrid system.The concentration of XG influenced the viscoelastic frequency dependence of the hybrid system significantly and complicatedly.After the addition of XG,the correlation between G′and frequency changed from negative to positive.

Biocompatible and antibacterial soy protein isolate/quaternized chitosan composite sponges for acute upper gastrointestinal hemostasis

Innovative biomedical applications have high requirements for biomedical materials.Herein,a series of biocompatible,antibacterial and hemostatic sponges were successfully fabricated for the treatment of acute upper gastrointestinal bleeding(AUGB).Quaternized chitosan(QC)and soy protein isolate(SPI)were chemically cross-linked to obtain porous SPI/QC sponges(named SQS-n,with n¼30,40,50 or 60 corresponding to the weight percentage of the QC content).The chemical composition,physical properties and biological activity of SQS-n were investigated.SQS-n could support the adhesion and proliferation of L929 cells while triggering no obvious blood toxicity.Meanwhile,SQS-n exhibited good broad-spectrum antibacterial activity against both grampositive bacteria(Staphylococcus aureus)and gram-negative bacteria(Escherichia coli).The in vivo hemostatic effect of SQS-n was evaluated using three different bleeding models.The results revealed that SQS-50 performed best in reducing blood loss and hemostatic time.The overall hemostatic effect of SQS-50 was comparable to that of a commercial gelatin sponge.The enhanced antibacterial and hemostatic activities of SQS-n were mainly attributed to the QC component.In conclusion,this work developed a QC-functionalized hemostatic sponge that is highly desirable for innovative biomedical applications,such as AUGB.

Emulsion-filled gels of soy protein isolate for vehiculation of vitamin D3:Effect of protein solubility on their mechanical and rheological characteristics

The aim of this study was to develop heat-induced gels of soy protein isolate(SPI)filled with Brazil nut oil emulsions encapsulating vitamin D3(VD3).Before gelation,dispersions produced with different SPI concentrations(11-15%,w/w)were subjected to different pretreatments(manual mixing or mechanical stirring at 800 rpm for 10,20,and 30 min)and had their protein solubility quantified.The application of mechanical stirring increased the solubility of proteins and decreased the average particle size,affecting the microstructure(observed by confocal laser scanning microscopy)and rheological properties(evaluated by uniaxial compression and small strain oscillatory tests)of the heat-set gels.The incorporation of emulsions(produced with Brazilian nut oil)into gels formed emulsion filled gels(EFGs),which presented higher Young’s moduli andσH in comparison to non-filled gels(NFGs),indicating that the oil droplets were active within the matrices.The properties of EFGs subjected to small strain oscillatory tests,varied with the pretreatment conditions and SPI concentrations,highlighting the high influence of protein solubility,matrix inhomogeneities,and droplet clustering for determining the properties of such complex systems.Also,the heat-induced emulsion-filled gels of SPI produced were effective in protecting VD3,presenting good retention after 30 days of storage under refrigeration,and represent promising alternative for the production of future food gelled products.

Fabrication of soy film with in-situ mineralized bioactive glass as a functional food for bone health

Delivery of nutrients through the oral route is considered to be the most admissible and preferred path as it follows the same natural process of food consumption in the body.To provide nutrition to the bone for overall good bone health,the present work aimed to fabricate soy films as a functional food for bone nutrition.The film formed was fortified with an in-situ mineralized bioactive glass (BG) network containing essential minerals required for good bone health.Also,vitamin K1 was supplemented into the films.Nutritional analysis depicted that the films are a rich source of protein containing about 67% of protein per 100 g having energy calories of 330 Kcal/100 g and essential micronutrients required for bones.The rheological studies depict viscoelastic hydrogel film-like properties of the functional soy-based film.The tensile strength of the said film is about 3.46 ± 0.17 MPa.The in-situ mineralization of the BG network in the soy protein matrix is responsible for the increased tensile strength and swelling properties of the functional film.The presence of essential oils in the film imparts antimicrobial properties to the film.Hence these soy films can be served as nutritional functional food having antimicrobial activity.

Effects of salt ions on rheological properties of SPI-GG hybrid system

The rheological characteristic of soy protein isolate(SPI),is one of the most important properties in its application in food industry.The effects of different concentrations of guar gum(GG,polysaccharide)and sodium chloride(salt ion)on the rheological properties of SPI were studied in this research.Steady-state shear,strain sweep and frequency sweep tests(static and dynamic rheological tests)were performed,and the following phenomenon and conclusions were drawn:(1)The viscosity of the hybrid system increases with the GG addition.This trend could also be seen with the appropriate adding of salt ion;(2)As the applied frequency increases,the storage modulus G′and the loss modulus G″of the hybrid system increase at a similar rate.And the frequency sweep parameters of the hybrid system rise significantly with the increase of both GG and ionic concentration;The frequency dependence of the system varies significantly with the addition of salt ion;(3)With the concentration of the salt ion increase,the storage module G′of the hybrid system decrease indicating that salt ion destroyed the network structure of hybrid dispersion to a certain extent.