Soy Protein Isolate Content Research Articles

Effect of Soy Protein Isolate on Pasting, Rheological, and Textural Attributes of Potato Starch

AbstractThe effects of different concentrations of soy protein isolate (SPI) on the functional, rheological, pasting, and structural properties of potato starch (PS) are investigated. The water and oil absorption capacity (OAC) of PS‐SPI mix increased significantly with the addition of SPI. Gel strength, peak, final, breakdown, and setback viscosity of PS decreases, whereas the pasting temperature increases with an increase in SPI fraction. Both the Herschel–Bulkley and power law model are found to equally fit in steady state rheology. The PS‐SPI blend exhibits pseudoplastic behavior. The addition of SPI decreases the storage (G′) and loss modulus (G″). SPI also lowers the flow stress values in the amplitude sweep test. Frequency sweep confirms the formation of weak gel formation in PS‐SPI blend by exhibiting a lower value of G′ and G″ than the pure starch. The microstructure of composite gel appears less dense with greater pore size than starch gel. The hardness of the SPI‐PS blend gel decreases from 6.76 to 0.85 N when the SPI content is increased from 0% to 50%. Fourier transform infrared (FTIR) confirms that no chemical groups are formed or destroyed during the composite gel‐making process.

Including protein hydrolysates during thermal processing mitigates the starch digestion of resulted starch-based binary matrix

Staple foods with starch and protein components are usually consumed after thermal processing. To date, how including protein hydrolysates (with varied hydrolysis degrees) tailors the structure and digestion features of starch-based matrix with thermal processing has not yet been sufficiently understood. Here, corn starch (CS), soy protein isolate (SPI), and soy protein isolate hydrolysates (SPIH) with different hydrolysis time (5–60 min) were used to prepare starch-based binary matrices. With the addition of SPI or SPIH during thermal processing, the resultant binary systems exhibited higher thermal stability (breakdown visibility was increased by 1.9–10.8 times), denser networks, and fewer short-range orders (R995/1022 was decreased by up to 15.3 %). These structural changes allowed an inhibited starch digestion within the binary system, especially with increased SPI or SPIH content. Compared with CS, the content of resistant starch (RS) for CS-SPI binary complex (10:3 w/w) increased from 9.89 % to 16.69 %. Compared to SPI, SPIH inclusion displayed a stronger inhibitory effect on starch digestion since the reduced molecule size of SPIH probably enhanced its interplays with starch or amylase. For instance, the 10:3 w/w starch-SPIH 60 binary matrix possessed the highest RS content (19.07 %).

Impact of soybean protein isolate on gluten‐free bread: a comprehensive study of physicochemical properties of gluten‐free dough and bread matrix properties

SummaryRice bread is an essential component of a healthy diet. However, due to the poor processing properties of rice protein and starch, it is difficult to form an effective gel network structure, resulting in poor quality of rice breads. This research investigated the impacts of soy protein isolate (SPI) on the physicochemical properties of rice dough and the quality of rice bread. The results suggested that adding SPI could refine the thermal stability of mixtures and delay the aging of starch compared with pure rice flour, indicating that adding SPI reduced the amylose concentration and inhibited starch interaction in the mixed rice powder system. The rheology and SEM analysis of doughs showed that the appropriate addition of SPI increased the elasticity, and reached the highest fermentation height and gas retention coefficient at 9% SPI content, which increased by 115.38% and 8.39%, respectively. In contrast, excessive SPI led to protein aggregation and weakened the structural strength of the dough. When adding 9% SPI improved the hardness, chewiness and specific volume of rice bread, significantly reduced the brightness and baking loss rate, and refined the performance and quality of rice bread. This study confirms that SPI can be used as an improver for good gluten‐free bread (GFB) through its good functional properties and action on starch and provides some basis for further investigation of the interaction between SPI as an improver and rice starch.

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.

Soy Protein Nanofibers Obtained by Solution Blow Spinning

The climate crisis, growing pollution of the environment with waste, and ubiquitous microplastics have encouraged the search for new methods and new opportunities to use natural materials in the least harmful processes. Replacing synthetic materials with raw materials is not only a matter of “fashion”, but also a necessity. Therefore, this study aimed to produce fibers from an aqueous solution containing the highest possible concentration of soy protein isolate (SPI) through solution-blowing. As the aqueous solution of SPI has no fiber-forming potential, polyethylene oxide (PEO) was used as the carrier/matrix. The rheology of the aqueous PEO solution and PEO/SPI blends (flow curves, loss modulus, and storage modulus) was then analyzed. The proportions of the PEO/SPI mixtures and the process parameters were determined on this basis. As a result of the conducted research, nanofibers were produced from water solutions of PEO/SPI with a soy protein content of up to 7.88%, with a PEO share of 1.25%. The average diameter of the obtained fibers was 225–495 nm, depending on the process parameters and SPI content—as the SPI content in the PEO/SPI mixture increased, the average fiber diameter decreased. The production of nanofibers with a high soy protein content increases their application possibilities. Firstly, due to a much larger surface area, and secondly, due to the presence of numerous functional groups in the protein structure, which can be a place of attachment for additional compounds that give the obtained nanofibers the desired properties.

Comparative Effect of Cricket Protein Powder and Soy Protein Isolate on Gel Properties of Indian Mackerel Surimi.

This work comparatively investigated the effects of different levels (0, 1, 3, and 5%, w/w) of cricket protein powder (CP) and soy protein isolate (SPI) on the gel properties of mackerel surimi. Both SPI and CP enhanced the rheological properties of surimi pastes during heating, as indicated by the increase in G' and G″ and the decrease in tan δ. With increasing SPI content, the proteolytic inhibition, gel properties, water-holding capacity, and textural profiles of surimi gel were markedly enhanced. Molecular driving-force results showed that SPI markedly promoted the hydrophobic interaction, while disulfide bonds were dominant in CP-added gel. However, the whiteness of surimi gels tended to decrease with the increased levels of both additives, in particular CP. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) demonstrated that SPI hindered the polymerization of myosin heavy chain while CP participated in the formation of non-disulfide covalent bonds with actin. Fourier transform infrared (FTIR) spectra indicated that CP and SPI did not influence the secondary structure of proteins in surimi. Scanning electron microscopy (SEM) demonstrated that CP or SPI induced the myofibrillar protein to form smoother and compact gel network structures. Overall acceptability of the mackerel surimi gel can be improved by the incorporation of 5% SPI while CP had a negative impact on several parameters. However, CP showed the remarkable ability to prevent the lipid oxidation of the gel after storage at 4 °C for 7 days. Overall, both SPI and CP demonstrated positive impacts on the gelling characteristics of mackerel surimi; however, SPI was more advantageous than CP in terms of the gel-strengthening effect and sensory qualities. This study offered a potential use for plant and insect proteins as functional and nutritional ingredients for the production of dark-fleshed fish surimi.

Steam‐exploded camellia (Camellia oleifera Abel.) seed protein improves the stability of camellia seed oil emulsions

SummaryWe aimed here to investigate the ability of steam‐exploded camellia seed protein (SECSP) in stabilising steam‐exploded camellia seed oil‐in‐water emulsion in comparison with soy protein isolate (SPI). Emulsions with different SECSP and SPI contents (0.5, 1, 1.5 and 2 g 100 mL−1) were formulated and the effect of protein concentration on emulsion droplet size, zeta (ζ)‐potential, physical stability and bioaccessibility was examined. The stability of emulsion increased with increasing protein concentration. SECSP emulsion was characterised by smaller droplet sizes, higher surface charge and better stability than SPI emulsion. Furthermore, SECSP emulsion exhibited good digestive stability. SECSP emulsion showed creaming only at protein concentrations above 0.5 g 100 mL−1 after 28 days of storage, while SPI emulsion showed stratification and flocculation during the same storage period. Hence, steam explosion pretreatment physical modification of camellia seed protein (CSP) provides a novel approach of utilising proteins for emulsions stabilisation, and digestive stability improvement under gastrointestinal conditions.

Influence of Carboxymethyl Cellulose on the Stability, Rheological Property, and in-vitro Digestion of Soy Protein Isolate (SPI)-Stabilized Rice Bran Oil Emulsion.

In this study, carboxymethyl cellulose (CMC) was added to soybean protein isolate (SPI)-stabilized rice bran oil (RBO) emulsion to improve its physicochemical stability and free fatty acid (FFA) release characteristics. RBO emulsions stabilized by SPI and various contents of CMC were prepared and assessed by measuring zeta potential, particle size, transmission, and microstructure, the rheological properties were analyzed by dynamic shear rheometer. In addition, its chemical stability was characterized by a storage experiment, and the FFA release was explored by a simulated gastrointestinal tract (GIT) model. It showed that the negative charge of the droplets of RBO emulsion was increased with increasing CMC content. The decrease in transmission of SPI-stabilized RBO emulsion with increasing CMC content was due to the droplets not being free to move by the special network interaction and an increase in the viscosity. According to the determination of the reactive substances of lipid hydroperoxide and thiobarbituric acid during 30 days storage at 37°C, the chemical stability of the emulsion added with CMC was enhanced compared with the SPI-stabilized RBO emulsion. In-vitro digestion studies not only evaluated the structural changes of RBO emulsions at different stages, but also found that RBO emulsion with CMC showed a higher level of free fatty acids release in comparison with that without CMC. It indicated that the utilization of CMC can improve the bioavailability of RBO emulsions.

Characterization of the Antimicrobial Edible Film Based on Grasshopper Protein/Soy Protein Isolate/Cinnamaldehyde Blend Crosslinked With Xylose.

A composite material based on a new insect-based grasshopper protein (GP)/soy protein isolate (SPI) blend has been studied by solution casting using xylose as a crosslinker and cinnamaldehyde (CIN) as an antimicrobial agent to develop a novel antimicrobial edible packaging. In this paper, the effects of SPI, xylose, and CIN content on the properties of edible film were studied. The tensile test confirmed that 30% SPI incorporation content had the best blending effect with the mechanical properties and barrier properties improving obviously. After adding 10% xylose to form crosslinking network, the tensile strength and elongation at the break of the film showed the best state increasing to 3.4 Mpa and 38%, respectively. The 30% CIN enabled the film to be resistant to Escherichia coli and Staphylococcus aureus strongly and decreased the water vapor permeability to 1.8 × 1011 (g/cm·s·Pa) but had a negative effect on the mechanical properties. This is the first time that edible insects have been used to produce the natural edible antimicrobial packaging, proving edible insects, an excellent protein source, are tipped to be a potential source of raw materials for biomaterials.

Water-Dispersible Phytosterol Nanoparticles: Preparation, Characterization, and in vitro Digestion.

For improving solubility and bioaccessibility of phytosterols (PS), phytosterol nanoparticles (PNPs) were prepared by emulsification–evaporation combined high-pressure homogenization method. The organic phase was formed with the dissolved PS and soybean lecithin (SL) in anhydrous ethanol, then mixed with soy protein isolate (SPI) solution, and homogenized into nanoparticles, followed by the evaporation of ethanol. The optimum fabrication conditions were determined as PS (1%, w/v): SL of 1:4, SPI content of 0.75% (w/v), and ethanol volume of 16 ml. PNPs were characterized to have average particle size 93.35 nm, polydispersity index (PDI) 0.179, zeta potential −29.3 mV, and encapsulation efficiency (EE) 97.3%. The impact of temperature, pH, and ionic strength on the stability of fabricated PNPs was determined. After 3-h in vitro digestion, the bioaccessibility of PS in nanoparticles reached 70.8%, significantly higher than the 18.2% of raw PS. Upon freeze-drying, the particle size of PNPs increased to 199.1 nm, resulting in a bimodal distribution. The solubility of PS in water could reach up to 2.122 mg/ml, ~155 times higher than that of raw PS. Therefore, this study contributes to the development of functional PS-food ingredients.

Hydroxypropyl Chitosan/Soy Protein Isolate Conduits Promote Peripheral Nerve Regeneration.

Designing scaffolds, with optimized microstructure and function for promoting the release of neuro-related factors, is significant in peripheral nerve regeneration. Herein, a series of hydroxypropyl chitosan/soy protein isolate composite sponges (HCSS) were fabricated by a freeze-drying technique. The physicochemical properties of the resultant HCSS were examined by a Fourier infrared spectrometer, X-ray diffractometer, scanning electron microscope, water absorption assay, water retention assay, and compressive strength assay. The results indicated that HCSS exhibited an interconnected porous microstructure and a high water retention ratio with the increase in soy protein isolate (SPI) content. The biological characterization found that the HCSS-50 containing 50% SPI content profoundly promoted the proliferation of RSC96 cells and the secretion of neuro-related factors without excessive reactive oxygen species production. In addition, HCSS-50 could significantly promote the expression of neuro-related factors; for example, the expression of TGF-β was three times higher than that of the control group. Finally, an optimized HCSS-based conduit was fabricated from HCSS-50 to repair sciatic nerve injury in rats with the combination of bone marrow mesenchymal stem cells (BMSCs) or BMSC-derived Schwann cells (SCs). The results suggested that the constructed HCSS-based conduit accompanying BMSC-derived SCs could effectively promote axonal regeneration and upregulate the expression of neuro-related factors such as Krox20, Zeb2, and GAP43. Collectively, a newly engineered nerve conduit system was developed by incorporating HCSS-50 and BMSC-derived SCs, which could be an alternative candidate for peripheral nerve regeneration. Impact statement Peripheral nerve repair is of paramount significance in the clinical. This work describes a hydroxypropyl chitosan/soy protein isolate conduit, which could effectively promote axonal regeneration and upregulate the expression of neuro-related factors. Thus, we provide a potential candidate for peripheral nerve regeneration.

Study of protein / k-carrageenan mixture's effect on low-fat whipping cream formulation

This work aimed to investigate the effect of protein/K-carrageenan mixture as replacement for dairy fat portion in whipping cream and to assess its effect on the final product's characteristics. During this study, a low-fat whipping cream was formulated. The removed fat content was substituted by a blend which contained water, soy protein isolate (SPI) and k-carrageenan gum (CG). The influence of SPI and CG content on the stability of the cream was investigated. A simplex–centroid design was used to evaluate the optimum formulation. Foaming properties, viscosity, textural properties and emulsions stability were determined. SPI significantly increased the flocculation of fat droplets. Formulation containing high level of CG was distinguished by decrease in overrun which was correlated with increase in the viscosity. The optimum formulation of fat substitute blend was found to contain 44.5% water, 46.4% SPI and 9% k-CG. Full fat cream provided about 235.88 kcal versus 161.63 kcal for the new formulation. This shrinkage in energetic value corresponds to 31.5% making possible to consider the new product as an alleviated food.

Effects of soy protein isolate on mechanical and hydrophobic properties of oxidized corn starch film

Oxidized corn starch (OS) has a good film-forming ability; however, its poor mechanical properties and moisture barrier are shortcomings. To improve the deficiencies of OS film, soy protein isolate (SPI) with different ratios (10%, 20%, and 30%) was incorporated into OS film at different pH values (6, 8, and 10) to investigate the mechanical and hydrophobic properties of the blended films. The blended films were characterized by water sensitivity, contact angle, mechanical properties, optical properties, and microstructure. The increases in the SPI ratio and pH reduced the moisture content and total soluble matter of the blended films. The reduction in water vapor permeability and the increase in contact angle from 37.3° to 104.5° suggested that the moisture barrier of the OS film was improved by SPI. The elongation at break of blended films increased, but the tensile strength decreased with increasing of SPI content and pH. The blended films prepared at pH 10 were more yellow and had higher transmittance. Scanning electron microscopy and atomic force microscopy showed that the blended films exhibited denser microstructures and smoother surfaces with the increasing pH. X-ray diffraction and thermogravimetric analysis implied that SPI interfered with the intermolecular interaction of OS.

Combining effect of soybean protein isolate and transglutaminase on the gel properties of Zhikong scallop (Chlamys Farreri) adductor muscle

The effects of soy protein isolate (SPI) in combination with transglutaminase (TGase) on the gel properties of Zhikong scallop (Chlamys farreri) adductor muscle were investigated. When 4 g/100 g SPI combined with 0.4 g/100 g TGase were added, the gel strength and water holding capacity (WHC) of heat induced Zhikong scallop adductor muscle gel was significantly improved. The textural profiles, such as hardness, cohesiveness, springiness and chewiness, reached their peaks as well. Although the whiteness continued to decrease with the increase of SPI content, TGase did not influence the whiteness of Zhikong scallop adductor muscle gel regardless of SPI levels. According to the results of LF-NMR, the free water was transformed into bound and immobilized water in gels containing SPI and/or TGase. SDS-PAGE showed that TGase would promote the cross-linking of SPI and Zhikong scallop adductor muscle protein, and offset the negative effects of excessive SPI. Further optical microscopy and SEM observed that the formation of the most compact network structure, which was caused by more inter- and intra-molecular cross-linking of proteins. The results suggested that the addition of 4 g/100 g SPI combined with 0.4 g/100 g TGase could effectively improve the gel properties of Zhikong scallop adductor muscle.

The Stability, Microstructure, and Microrheological Properties of Monascus Pigment Double Emulsions Stabilized by Polyglycerol Polyricinoleate and Soybean Protein Isolate.

Monascus pigment is a natural food pigment and is commonly used for coloring and as antiseptic of cured meat products, confectionery, cakes, and beverages. However, Monascus pigment is sensitive to environmental conditions. The main aim of this study was to investigate the effect of polyglycerol polyricinoleate (PGPR) and soy protein isolate (SPI) on the particle size, zeta potential, physical stability, microstructure, and microrheological properties of Monascus pigment double emulsions. The effects of ionic strength, heating, and freeze thawing treatment on the stabilities of Monascus pigment double emulsions were also characterized. It was found that the optimum PGPR and SPI concentrations for fabricating Monascus pigment double emulsion were 3.6 and 3.0 wt%, respectively. The fabricated Monascus pigment double emulsion was composed of fine particles with narrow and uniform size distributions. Microrheological property results suggested that the elastic characteristic of the Monascus pigment double emulsion was dominated with increasing PGPR and SPI contents. It was mainly due to the increased collision and interaction between the droplets during the movement resulting in force increasing. Monascus pigment double emulsions with <5 mM CaCl2 prevented calcium to destroy the physical stability of emulsions, while Monascus pigment double emulsions with more than 10 mM CaCl2 formed creaming. After freeze thawing treatment, creaming occurred in Monascus pigment double emulsion. However, it was stable against heating treatment due to heating leading to a dense network structure. It could be contributed to the practical applications of Monascus pigment double emulsions in food products.

A biodegradable soy protein isolate-based waterborne polyurethane composite sponge for implantable tissue engineering.

A biodegradable soy protein isolate-based waterborne polyurethane composite sponge (SWPU) was prepared from soy protein isolate (SPI) and polyurethane prepolymer (PUP) by a process involving chemical reaction and freeze-drying. Effects of SPI content (0, 10%, 30%, 50%, 70%) on the micro-structure and physical properties of the composite sponges were characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA). The results showed that the reaction between -NCO of PUP and -NH2 of SPI formed porous SPI-based WPU composite sponges. The results of the water absorption ratio measurement, solvent resistance measurement and compressive testing showed that water absorption, hydrophilicity, and tensile strength in the dry state of the composite sponges increased with the increase of SPI content. Especially, the tensile strength ranged from 0.3 MPa to 5.5 MPa with the increase in SPI content. The cytocompatibility and biodegradability of the composite sponges were evaluated by in vitro cell culture and in vivo implantation experiments. The results indicated that a certain SPI content in the sponges could promote the adhesion, growth, and proliferation of cells, enhance the cytocompatibility and accelerate the degradation speed of composite sponges. During the in vivo implanting period within 9 months, SWPU-50 sponge containing 50% of SPI brought out the lowest activated inflammatory reaction, most newly-regenerated blood capillaries, and best histocompatibility. All results indicated that SWPU-50 composite sponges had greatest potential for tissue engineering.

Fabrication of Hydroxypropyl Chitosan/Soy Protein Isolate Hydrogel for Effective Hemorrhage Control.

Hemostatic materials are increasingly important in civilian and military clinics. In this work, a hydrogel was fabricated from hydroxypropyl chitosan (HPCS) and soy protein isolate (SPI) through the crosslinking of epichlorohydrin. Effects of SPI content on the structure, and physical and biological properties of the prepared hydrogels were characterized using Fourier-transform infrared spectroscopy, X-ray diffractometry, scanning electron microscopy, water uptake testing, mechanical properties testing, MTT assay, hemolysis ratio testing, and routine blood coagulation test. The results indicated that the hydrogels showed high water uptake ability and compressive strength. The in vitro biocompatibility evaluation revealed that the hydrogel contains 30% SPI content (HCSH-30), could promote blood coagulation and cell proliferation. Furthermore, the hemostatic model of liver in New Zealand rabbit was applied to assess the hemostatic efficacy of the hydrogels. The results demonstrated that HCSH-30 stopped bleeding in 75 ± 1.63 s and improved hemostasis as compared with medical gauze. Thus, the HPCS/SPI hydrogel is expected to be a potential candidate for effective hemorrhage control. Impact statement Stoppage of bleeding is of paramount clinical significance in prophylactic, surgical, and emergency scenarios. This work describes a hydroxypropyl chitosan (HPCS)/soy protein isolate hydrogel, which could promote blood coagulation and cell proliferation, as well as stop bleeding in 75 ± 1.63 s on the liver of New Zealand rabbits. Thus, we provide a new candidate for hemostatic material and broaden the application of HPCS-based materials.

Plant protein modified natural cellulose with multiple adsorption effects used for bilirubin removal

In this study, bacterial cellulose (BC)/soy protein isolate (SPI) composite membranes were prepared by in situ cross-linked polymerization, and used as efficient blood compatible adsorbents to remove bilirubin. The obtained composite membranes were successively characterized by FTIR, SEM, AFM, contact angle test and hemolysis assay, which exhibited unique protein coated 3D fibrous network structures, hydrophobic surfaces and outstanding blood compatibility due to the incorporation of SPI. The BC/SPI membranes with high SPI content showed high adsorption efficiency, short adsorption equilibrium time (2 h) and multiple adsorption effects on bilirubin. The adsorption rate for free bilirubin of BC/SPI5 membrane could reach 78.8% when the bilirubin concentration was 100 mg L−1, while it increased to over 96.5% when the initial bilirubin concentration exceeded 400 mg L−1. More importantly, the BC/SPI5 membrane still exhibited high adsorption rate (over 70%) in presence of albumin. Furthermore, the composite membrane could also maintain high dynamic adsorption efficiency in self-made hemoperfusion devices. This novel naturally-derived membrane is an economical and efficient absorbent for the remove of bilirubin, and will provide new ideas for therapy of hemoperfusion without plasma separation process.

Biomimetic mineralization of novel hydroxyethyl cellulose/soy protein isolate scaffolds promote bone regeneration in vitro and in vivo

Although various strategies have been utilized to accelerate bone regeneration in bone tissue engineering (BTE), the treatment and repair of large bone defects remains a clinical challenge worldwide. Inspired by the natural extracellular matrix of bone tissue, organic-inorganic composite scaffolds with three-dimensional (3D) porous structures, sufficient mechanical properties, excellent cytocompatibility, osteoconductivity, and osteogenic potential have received considerable attention within the field of bone engineering. In this work, a novel epichlorohydrin (ECH)-crosslinked hydroxyethyl cellulose (HEC)/soy protein isolate (SPI) porous bi-component scaffold (EHSS) with hydroxyapatite (HAp) functionalization (EHSS/HAp) was constructed for bone defect repair via the combination of lyophilization and in situ biomimetic mineralization. Systematic characterization experiments were performed to assess the morphology, HAp-forming properties, mechanical properties and degradation rate of the scaffold. The results indicated that the prepared scaffolds exhibited an interconnected porous structure, a biomimetic HAp coating on their surfaces, improved mechanical properties in compression and a controllable degradation rate. In particular, semiquantitative analysis showed that the calcium/phosphorus (Ca/P) ratio of EHSS/HAp with 70% SPI content (1.65) was similar to that of natural bone tissue (1.67) according to energy dispersive X-ray spectroscopy analysis. In vitro cell culture experiments indicated that the EHSS/HAp with 70% SPI content showed improved cytocompatibility and was suitable for MC3T3-E1 cell attachment, proliferation and growth. Consistently, in vitro osteogenic differentiation studies showed that EHSS/HAp with 70% SPI content can significantly accelerate the expression of osteogenesis-related genes (Col-1, Runx2, OPN, and OCN) during osteogenic differentiation of MC3T3-E1 cells. Furthermore, when applied to the repair of critical-sized cranial defects in a rat model, EHSS/HAp with 70% SPI was capable of significantly promoting tissue regeneration and integration with native bone tissue. Microscopic computed tomography (micro-CT) results demonstrated that the bone defect site was nearly occupied with newly formed bone at 12 weeks after implantation of EHSS/HAp with 70% SPI content into the defect. Hematoxylin and eosin (H&E) staining and Masson's trichrome staining of histological sections further confirmed that EHSS/HAp with 70% SPI markedly promoted new bone formation and maturation. Collectively, our results demonstrate the potential of EHSS/HAp scaffolds with 70% SPI for successful bone defect repair and regeneration.

A rheological approach to 3D printing of plasma protein based doughs

3D-printing, also known as additive manufacturing, is a polymeric processing technique whose use has been increasing strongly in recent decades. Because of its customizing potential, it is being widely applied in a great variety of fields, such as medicine, engineering, microelectronic, or food. The present work was focused on the determination of the rheological properties required for certain protein-based doughs (from blood plasma, pea and soy) to flow adequately during the 3D-printing process. Eventually, the formulations that resulted in conveniently shaped items, i.e., that reproduced the desired pattern, were selected. Using glycerol (Gly) as a plasticizer, the printability of doughs with different porcine plasma protein (PPP) contents was initially tested by rheology methods. Only doughs with a PPP content comprised between 42.5 and 47.5 wt % resulted in a successful printing. Then, part of PPP was replaced by a pea protein concentrate (PPC) or a soy protein isolate (SPI), keeping an overall biopolymer content of 45 wt % within the dough. Mixed doughs were properly printed, up to a PPC or SPI content of 10 or 15 wt % within the biopolymer fraction, respectively, displaying all printable doughs similar textural profiles (low firmness, high adhesivity). The building of printability maps for the protein-based doughs studied emphasizes the importance of controlling the rheological properties of protein-based doughs.