Functional Properties of Soy Protein Isolates Prepared from Gas-Supported Screw-Pressed Soybean Meal

White flakes (WFs) are obtained from dehulled flaked soybeans by extracting oil with hexane and flash- or downdraft-desolventizing the (defatted) flakes, and WFs are the normal feedstock used to produce soy protein ingredients. Gas-supported screw pressing (GSSP) is a new oilseed crushing technology in which traditional screw pressing is combined with injecting high-pressure CO₂, thereby producing hexane-free, low-fat, high-PDI soybean meal. The objectives of the present study were to evaluate yields, compositions, and functional properties of soy protein isolates (SPIs) produced from GSSP soybean meal and to compare these properties to those of SPIs produced from WFs. GSSP meals produced SPIs in significantly higher yields (59.7–63.1% vs. 51.6–61.1%), with greater free (0.05–0.40%) and bound fat (3.70–4.92%) contents than did WFs. There were no significant differences in protein contents of the SPI; all exceeded 90% protein content (db). SPIs prepared from GSSP meals had similar or slightly lower water-solubilities compared to SPIs prepared from WFs. SPIs prepared from GSSP meals had higher water-holding capacities and viscosities, and significantly better emulsifying and fat-binding properties compared to SPIs prepared from WFs. SPIs prepared from WFs had significantly better foaming properties compared to SPIs prepared from GSSP meals, which were attributed to the lower fat contents of SPIs prepared from WFs.     

Functional Properties of Protein Isolates Produced by Aqueous Extraction of De-hulled Yellow Mustard

Two types of protein isolates were prepared from de‐hulled yellow mustard flour by aqueous extraction, membrane processing and isoelectric precipitation. The precipitated and soluble protein isolates had 96.0 and 83.5% protein content on a moisture and oil free basis, respectively. Their functional properties were evaluated and compared with commercial soybean and other Brassica protein isolates. The soluble protein isolate exhibited high values for all properties. The precipitated protein isolate showed excellent oil absorption and emulsifying properties but poor solubility, water absorption and foaming properties due to its high lipid content (~25%). Storage temperature had limited effect on lipid oxidation, and hence the stability of the precipitated protein isolate at 25–45 °C. Flavor of wieners and bologna prepared with 2% of this isolate as binder was comparable to those prepared with soy protein isolate.     

Composition, Structure and Functional Properties of Protein Concentrates and Isolates Produced from Walnut (Juglans regia L.)

In this study, composition, structure and the functional properties of protein concentrate (WPC) and protein isolate (WPI) produced from defatted walnut flour (DFWF) were investigated. The results showed that the composition and structure of walnut protein concentrate (WPC) and walnut protein isolate (WPI) were significantly different. The molecular weight distribution of WPI was uniform and the protein composition of DFWF and WPC was complex with the protein aggregation. H(0) of WPC was significantly higher (p < 0.05) than those of DFWF and WPI, whilst WPI had a higher H(0) compared to DFWF. The secondary structure of WPI was similar to WPC. WPI showed big flaky plate like structures; whereas WPC appeared as a small flaky and more compact structure. The most functional properties of WPI were better than WPC. In comparing most functional properties of WPI and WPC with soybean protein concentrate and isolate, WPI and WPC showed higher fat absorption capacity (FAC). Emulsifying properties and foam properties of WPC and WPI in alkaline pH were comparable with that of soybean protein concentrate and isolate. Walnut protein concentrates and isolates can be considered as potential functional food ingredients.     

Properties of Soy Protein Produced by Countercurrent,Two-Stage,Enzyme-Assisted Aqueous Extraction

Enzyme-assisted aqueous extraction processing (EAEP) is an environmentally friendly technology where oil and protein can be simultaneously extracted from soybeans by using water and protease. Countercurrent, two-stage, EAEP was performed at a 1:6 solids-to-liquid ratio, 50 °C, pH 9.0, and 120 rpm for 1 h to extract oil and protein from soybeans. The skim fractions were produced by three methods: (1) by treating with 0.5 % protease (wt/g extruded flakes) in both extraction stages; (2) by treating with 0.5 % protease in the 2nd extraction stage only; and (3) by using the same two-stage extraction procedure without enzymes in either extraction stages. Countercurrent, two-stage, protein extraction of air-desolventized, hexane-defatted, soybean flakes was used as a control. Solubility profiles of the skim proteins were the typical U-shaped curves with the lowest solubility at the isoelectric point of soy protein (pH 4.5). The use of the enzyme slightly improved solubility of the recovered protein with hydrolyzed proteins having higher solubilities at acid pH. Emulsification and foaming properties were generally reduced by the use of enzyme during EAEP extractions. The skims produced with protease-extracted (hydrolyzed) proteins gave gels with lower hardness than did unhydrolyzed proteins when heated at 80 °C. The essential amino acid compositions and protein digestibilities were not adversely affected by either extrusion or extraction treatments.     

Comparison of Flavor Volatiles and Some Functional Properties of Different Soy Protein Products

Flavor volatiles profiles and some functional properties of soy protein products produced by five different extraction methods were studied. A method, consisting of Ethanol Washing and a Hydrothermal cooking Treatment, was proposed to produce a soy protein product (EWHT). Flavor volatiles profiles, emulsifying ability and whiteness of EWHT were improved in comparison with those of Acid Precipitated soy protein product (AP), soy protein product with Oil-Body Associated proteins and Polar Lipids removed (OBA/PL-less), soy protein product obtained from Countercurrent Extraction (CE) and Oil-Body Associated protein product with Polar Lipids (OBA/PL). The GC-MS and sensory analysis showed that the flavor volatiles content of EWHT was lower than that of the other soy protein products. The results from high performance size exclusion chromatography and dynamic light scattering showed that proteins with larger molecular weights and larger hydrodynamic radii were contained in EWHT, suggesting that EWHT formed soluble larger protein aggregates with a more flexible structure, thus the solubility of EWHT was similar to that of AP, OBA/PL-less and CE. The surface hydrophobicity of EWHT (994.8) was higher than that of the other soy protein products. Therefore the process for preparing EWHT can be an ideal processing method to produce soy protein with good quality relative to flavor and functionality.     

Studies on Extraction of Protein Isolates from Turkish sunflowerseed and Cottonseed Extraction Cakes and on their Functional Properties

In this study trials have been made to produce protein isolates from sunflowerseed and cottonseed cakes which are two of the three major edible oil sources of Turkey, besides olive. Our experiments yielded the best solvent systems for extraction, the optimum H values for protein precipitation for each seed cake. Using these optimum parameters, we could succeed in extracting about 55% of the proteins contained in the cakes, and preparing isolates which contained more than 90% protein. The functional properties of the obtained isolates, such as protein dispersibility index, water and oil adsorption capacities and emulsion activity were determined. the amino acid compositions of the oilseed cakes as well as of the respective protein isolates were also determined and compared to the FAO protein reference model.     

Protein Subunit Composition Effects on the Thermal Denaturation at Different Stages During the Soy Protein Isolate Processing and Gelation Profiles of Soy Protein Isolates

This study focussed on the evaluation of thermal denaturation at three different stages during soy protein isolation and the effect of subunit composition on the formation of heat-induced soy protein gels. Soy protein isolates (SPI) were prepared from 12 high protein lines, Harovinton variety and 11 derived null-lines which lacked specific glycinin (11S) and β-conglycinin (7S) protein subunits. Protein denaturation during SPI processing was monitored by differential scanning calorimetry (DSC). The results showed that hexane extraction of oil from soybean flours at 23 °C or 105 °C did cause changes in protein conformation. Rheological measurements showed that lines with different subunit compositions and 11S:7S ratio had distinctive gelation temperatures and resulted in gels with different network structures. All lines formed particulate gels at 11% protein. The 11S:7S ratio was not correlated to final stiffness, measured as the storage modulus G′, of SPI gels. Lower gelation temperatures were usually observed for 7S-rich lines. The absence of A3 and the combination of A1, A2 and A4 subunits of 11S fraction may suggest the formation of stiffer gels. A more detailed study of the frequency dependence of G′ for the various networks formed also indicated that differences in subunit composition influenced the network structures.     

大豆蛋白质塑料加工和力学性能的研究

采用HAAKE扭矩流变仪研究了增塑型、还原剂和润滑剂等对大豆蛋白质塑料扭短流变性能的影响,并在此基础上,对经HAAKE密炼并模压制得的大豆蛋白质塑料力学性能作了测试。     

大豆蛋白/苎麻复合材料的制备及性能研究

采用化学、填充的方法制备大豆蛋白(SPI)与苎麻(RF)复合材料以改善大豆蛋白塑料的力学性能。通过扫描电子显微镜(SEM)、电子万能试验机、熔体流动速率仪等实验仪器研究复合材料的形态结构、力学性能和流变性能,并测定了复合材料的吸水率。试验结果表明,添加苎麻纤维对大豆蛋白的增强增韧效果都比较显著,硬度和拉伸强度对比纯大豆蛋白材料有了很大的提高,并且得到了苎麻增强增韧大豆蛋白材料的最佳用量,当苎麻的用量分别为10份时,复合材料的拉伸强度和硬度达到最佳,对复合材料吸水率的测定也较改性前有了很大的改善。     

PAPI改性大豆蛋白复合材料的制备与性能研究

以大豆分离蛋白（SPI）和多亚甲基多苯基异氰酸酯（PAPI）为原料,制备了改性大豆蛋白,再加入聚己内酯（PCL）,经过模压成型制备了改性大豆蛋白复合材料,并对其力学性能、微观结构和热性能进行了表征。结果表明,随着PAPI的加入,材料的力学性能得到很大程度的改善,拉伸强度由9.65 MPa上升到32 MPa,冲击强度由1.36 kJ/m2提高到11.7 kJ/m2;随着PAPI的加入,大豆蛋白材料的吸水性也有明显的改善,24 h吸水率从33.89 %下降到9.77 %;红外光谱分析表明,PAPI可以与大豆分离蛋白发生反应,改变了大豆蛋白的结构,并影响其性能,使复合材料内部结构更加致密。     

Structure and Properties of Soy Protein Plastics Plasticized with Acetamide

Summary: Acetamide‐plasticized SPI sheets, denoted SAm, were prepared by compress molding at 140 °C and 20 MPa. The compatibility between acetamide and SPI has been investigated by DSC, WXRD, optical transmittance and SEM. Strong hydrogen bonding interaction between SPI and acetamide was evidenced by FT‐IR spectroscopy. When acetamide contents reached 30 phr the SAm exhibited best plasticity, leading to the highest elongation at break (178%) of the material. Moreover, the single glass transition temperatures of the SAm sheets decreased with an increase of acetamide content. Furthermore, the results from torque rheology revealed that the flexibility and processability were improved when the acetamide contents increased from 10 to 50 phr. Interestingly the acetamide‐plasticized SPI materials had better optical transmittance at 800 nm (75%) than that of glycerol‐plasticized SPI sheet, indicating a good compatibility of the SAm materials. At the same time, the results from TGA measurement and the water uptake indicated that SAm sheets possessed higher thermal stability and water‐resistance than those of glycerol‐plasticized SPI. This work provided a good plasticizer for SPI, and it is anticipated to use in biodegradable protein materials widely.

Water uptake of the SAm sheets at 35% RH.     

大豆蛋白/亚麻复合材料的制备及性能研究

针对大豆蛋白塑料力学性能较差的问题,采用化学、填充的方法制备大豆蛋白与亚麻复合材料。通过扫描电子显微镜、电子万能试验机、熔体流动速率仪等实验仪器研究复合材料的形态结构、力学性能和流变性能,并测定了复合材料吸水率。研究结果表明,添加亚麻纤维对大豆蛋白的增强增韧效果都比较显著,硬度和拉伸强度对比纯大豆蛋白材料有了很大的提高,并且得到了大豆蛋白/亚麻复合材料的最佳用量,当亚麻的用量为6份时,复合材料的拉伸强度和硬度达到最佳,复合材料吸水率也较改性前有了很大的改善。     

大豆分离蛋白/聚乙烯醇塑料的制备及性能研究

将聚乙烯醇（PVA）按不同比例与大豆分离蛋白(SPI)混合,采用丙三醇作为增塑剂,经模压成型制备SPI/PVA塑料,采用X射线衍射仪、动态热机械分析仪、差示扫描量热仪、万能电子拉力试验机、扫描电子显微镜等研究了SPI/PVA塑料的结构、形态和性能。结果表明,丙三醇增塑的SPI会出现微相分离,即出现富丙三醇微区和富蛋白微区,而PVA的加入主要破坏了SPI在富丙三醇微区的晶体结构,并使富丙三醇微区的玻璃化转变温度向高温方向偏移。PVA的加入还明显提高了SPI/PVA塑料的拉伸强度,当PVA含量为1份时,其拉伸强度比纯SPI塑料提高了41.5 %;PVA的加入对SPI/PVA塑料的吸水性也有明显改善,其24 h吸水率从134.86 %下降到77.38 %。     

Protein Isolates from New Varieties of Rapeseed

Defatted meals of two varieties of rapeseed, Brassica napus, Erglu and Lesira, were used for the isolation of proteins. The protein isolates, obtained in high yields, are light colored, bland products having foam stability higher than soybean protein. Their amino acid composition shows adequate amounts of isoleucine and sulphur amino acids which seem to be limiting in rapeseed meal. Rapeseed meal and protein isolates prepared therefrom, were fed to chicks that had been depleted of their embryonic protein reserve. Feed consumption, weight gain and protein efficiency ratio reveal better performance of the protein isolates as compared to the corresponding meals. Erglu meal, too, is eminently suitable as supplement to chicken feed, whereas Lesira meal shows detrimental effects, probably due to its high glucosinolate content.     

Recovery and Functional Properties of Soy Storage Proteins from Lab- and Pilot-Plant Scale Oleosome Production

The aim of this study was to investigate soy protein recovery feasibility after lab- and pilot-plant scale oleosome isolation. The proteins were isolated by isoelectric precipitation and by ultrafiltration. The functional properties of the recovered proteins were compared to soy protein isolate produced in our laboratory. The residual lipid content in the aqueous supernatant affected the protein recovery yields and purities. Ethanol precipitation and ultrafiltration resulted in the best protein yields, which were 25 and 26% greater than protein yield obtained by isoelectric precipitation with distilled water dilution. The protein content of the isoelectric precipitated pilot-plant supernatant was higher (98%) than the protein content of ethanol-precipitated proteins (80%). Sodium dodecyl sulfate-polyacrylamide gel electrophoresis showed similar peptide profiles for laboratory and pilot-plant supernatants. Protein solubility curves between pH 3 and 8 were typical for soy protein isolate with higher solubilities for proteins obtained from pilot-plant supernatant. The soy protein isolate and ethanol-precipitated protein had the highest emulsification capacity on a dry-weight basis. These desirable functional properties of proteins recovered as co-products after oleosome isolation suggest they are highly suitable for industrial application as food ingredients and their recovery would contribute to the economics of the overall oleosome fractionation process.     

Physicochemical Properties and ACE-I Inhibitory Activity of Protein Hydrolysates from a Non-Genetically Modified Soy Cultivar

Arkansas‐grown non‐genetically modified soybean cultivar, R08‐4004, was selected to prepare a protein isolate, which was treated with Alcalase for limited enzymatic hydrolysis. The objective was to optimize the Alcalase hydrolysis condition to produce soy protein hydrolysate (SPH) with high protein yield, low bitterness, and clarity for beverage applications. The degree of hydrolysis ranged between 14 and 52 % during the study at varying incubation times using two different concentrations of Alcalase enzyme. Recovery of soluble protein, between 21 and 53 %, was achieved with a decrease in turbidity. There was an increase in surface hydrophobicity (S₀) which is correlated with bitterness of SPH treated with 1.0 AU (3.2 µL/g) of Alcalase 2.4 L. The sodium dodecyl sulfate‐polyacrylamide gel electrophoresis analysis showed a distinct hydrolysis pattern in which 7S globulin and the two acidic sub‐units of 11S globulin were hydrolyzed extensively in comparison to the two basic sub‐units of 11S globulin. Limited enzymatic hydrolysis produced low molecular weight peptides <17 kDa. Among these SPHs, the one derived after 120 min incubation had the highest soluble protein yield (43 %), low S₀ value (35.4), low turbidity (0.88), and highest angiotensin‐I converting enzyme (ACE‐I) inhibition activity (66.6 %). This hydrolysate has potential use as protein rich nutraceutical for developing many non‐genetically modified food product applications.     

硬脂酸对大豆蛋白质塑料性能的影响

对水的敏感性是阻碍大豆蛋白质降解塑料广泛应用的不利因素,为了克服这一缺点,实验固定甘油和大豆蛋白质的比例,通过添加硬脂酸与大豆蛋白质共混,研究了其添加量对机械性能和吸水率的影响。同时拉伸和红外、扫描电镜等实验表明甘油、硬脂酸对膜的力学性能、吸水率、断面形态、红外图谱均有影响。     

脲变性大豆蛋白塑料的性能和结构研究

将脲作为变性剂添加到大豆蛋白中,制备了脲变性大豆蛋白塑料,并研究了该变性大豆蛋白塑料的力学性能、动态力学性能、吸水性能、热稳定性以及微观结构和形貌。结果表明:当脲含量为27.0%时,该变性大豆蛋白塑料具有最大的断裂伸长率和断裂能,其玻璃化转变温度比非变性大豆蛋白塑料低98.3℃;随着脲含量的增加,材料的2 h吸水率和24 h吸水率均有所降低,其耐水性明显得到改善;当脲含量为9.0%时,同非变性大豆蛋白塑料相比,变性大豆蛋白塑料的热稳定性下降,而且其热失重曲线中最大失重速率所对应的温度高于脲的分解温度;红外光谱和扫描电镜结果表明,由于大豆蛋白与脲之间的氢键作用,使大豆蛋白之间的氢键被破坏,进而改善了大豆蛋白塑料的韧性。     

多重改性大豆分离蛋白可降解材料性能研究

大豆分离蛋白(SPI)经四氢呋喃、乙酸锌、顺丁烯二酸酐多重改性后,用水和甘油增塑,然后经热压制得力学性能和抗水性能良好的可生物降解材料。研究了四氢呋喃、乙酸锌、顺丁烯二酸酐用量对SPI可生物降解材料力学性能、抗水性能的影响。结果表明:当改性剂四氢呋喃、乙酸锌、顺丁烯二酸酐的用量分别为大豆分离蛋白的267%、7%和15%时,SPI可降解材料的性能最佳,其断裂伸长率、拉伸强度、吸水率和耐水指数分别为187.12%、9.29 MPa、30.9%和0.48。     

Adhesion and Physicochemical Properties of Soy Protein Modified by Sodium Bisulfite

Soy protein adhesives with a high solid content (28–39 %) were extracted from soy flour slurry modified with sodium bisulfite (NaHSO₃) at different concentrations. 11S‐dominated soy protein fractions (SP 5.4) and 7S‐dominated soy protein fractions (SP 4.5) were precipitated at pH 5.4 and pH 4.5, respectively. The objective of this work was to study the effects of NaHSO₃ on adhesion and physicochemical properties of soy protein. The adhesion performance of NaHSO₃‐modified SP 4.5 was better than SP 5.4; the wet strength of these two fractions was from 2.5 to 3.2 MPa compared with 1.6 MPa of control soy protein isolate. SDS‐PAGE results revealed the reducing effects of NaHSO₃ on soy protein. The isoelectric pH of soy protein decreased as NaHSO₃ increased due to the induced extra negative charges (RS‐SO₃^?) on the protein surface. The rheological properties of soy protein adhesives were improved significantly. Unmodified samples SP 5.4 and SP 4.5 had clay‐like properties and extremely high viscosity, respectively; with 2–8 g/L NaHSO₃ modification, both SP 5.4 and SP 4.5 had a viscous cohesive phase with good flowability. Overall, NaHSO₃‐modified soy protein adhesives in our study have many advantages over the traditional soy protein isolate adhesive such as better adhesion performance, higher solid content but with good flowability and longer shelf life.