Phosphorus flow in production of soy protein concentrate and isolate from defatted soybean flour

Implications of excess phosphorus (P) in waste streams obtained from soy-based protein preparation processes on the environment and their potential utilization as P-source are two significant understudied areas. Soybean-based protein ingredients for food products retain comparatively enhanced functional properties and are cheaper than other plant-based proteins. Soybean protein can be extracted and utilized as a food ingredient primarily by preparing soy protein concentrates (SPC) and soy protein isolates (SPI) from soybean meal/defatted soy flour (DSF). In a typical soybean processing facility, along with the soy products and soy-protein preparations, the recovery of phosphorus as a coproduct will enhance the economic feasibility of the overall process as the recovered P can be used as fertilizer. In this study, the SPC and SPI were prepared from the DSF following widely used conventional protocols and P flow in these processes was tracked. In SPC production, ~59% of the total P was retained with SPC and ~34% was in the aqueous waste streams. For SPI process ~24% of total P was retained with SPI and ~59% went in the waste solid residue (~40%) and aqueous streams (~19%). About 80%–89% P removal from the waste aqueous streams was achieved by Ca-phytate precipitation. This work demonstrated that in the process of SPC and SPI preparation the phosphorus from the waste aqueous streams can be precipitated out to avoid subsequent eutrophication and the waste solid residue with ~40% P can be reused as a P-fertilizer as other applications of this residue are unspecified.     

Refunctionalization of extruded-expelled soybean meals

Soybean meals produced by extruding-expelling (FF) have poor functional properties due to heat denaturation of the proteins, which limits their utilization in foods. Hydrothermal cooking (HTC), a treatment in which steam (150°C) and high shear are applied to a slurry of soybean meal, was used to refunctionalize EE protein meals. Two EE samples with protein dispersibility indexes (PDI) of 35 and 60 were used, along with solvent-extracted white flakes and full-fat whole soy meal as controls. Two HTC methods were explored: One method used a treatment temperature of 154°C and seven different residence times, controlled by varying the holding tube length; the other involved flashing the treated slurry directly into the atmosphere without any back-pressure regulation or holding. Effects of residence time on functional properties of the samples were investigated. The maximum effect of HTC conducted with the use of holding tubes (with-holding-tube HTC) was also compared with that of flash-out HTC. Solid dispersibility, protein dispersibility, and emulsification capacity of both EE meals were significantly improved by both types of HTC treatments. The flash-out HTC showed more benefits than the with-holding-tube HTC in refunctionalizing heat-denatured EE protein. For example, the solid dispersibility, protein dispersibility, and emulsification capacity of EE meal with PDI of 35 were improved 2.0, 4.4, and 2.1 times, respectively, by flash-out HTC treatment. Therefore, the HTC refunctionalization was proved effective in partially restoring the functional properties of the heat-denatured soy proteins.     

神府煤对大豆分离蛋白质的吸附特性研究

采用静态吸附法探讨了神府煤粉(SFC)对大豆分离蛋白质(SPI)的吸附特性。研究了SPI溶液初始质量浓度(3.0—12.0 kg/m3)、温度(20、30、40、50℃)、pH值(4.0—9.0)等条件对吸附量的影响。结果表明,吸附平衡时间为12 h,适宜的pH值为6.0。SFC对SPI吸附过程为非自发的放热过程,吸附过程符合二级动力学模型。红外光谱分析表明,蛋白质分子主要通过C O和NH与煤大分子结构中的OH和C O对应形成2个活性位点的氢键作用,吸附于煤表面。     

Graft polymerization of styrene on soy protein isolate

The grafting of styrene on soy protein isolate (SPI) in an 8 moL/L urea aqueous solution initiated by ammonium cerous nitrate and potassium persulfate was studied. The grafted copolymers were characterized by IR spectroscopy and DSC. The results indicated that styrene was grafted on the SPI. The influence of the reaction conditions on the grafting and efficiency percentages was investigated. The grafting and efficiency percentages initially increased and then decreased with the increase of the initiator concentration, monomer concentration, and reaction temperature. With the increase of reaction time, the grafting and efficiency percentages increased. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 1457–1461, 2005     

甲基丙烯酸缩水甘油酯对大豆蛋白塑料改性作用研究

用模压的方法制备了甲基丙烯酸缩水甘油酯(GMA)改性大豆分离蛋白质(SPI)塑料。表征了GMA改性SPI塑料的力学性能、耐水性,并分析了GMA与SPI之间的相互作用。结果表明GMA在模压过程中,环氧基与蛋白质分子间发生接枝和交联反应,同时自聚,在GMA含量较低时可以同时对SPI塑料起到增强和增塑作用,但是随着GMA含量增加,交联作用增强,塑料的断裂伸长率下降。     

Preparation and characterization of soy protein isolate films modified with sorghum wax

The effect of increasing the concentration of sorghum wax paste on the characteristics of soy protein isolate (SPI) films was investigated. Water vapor permeability (WVP), tensile strength (TS), elongation at break (E), and total soluble matter (TSM) of cast SPI films were determined. Sorghum wax paste extracted with ethanol was added to film-forming solutions of SPI at 5, 10, 15, or 20% w/w of protein. As the concentration of wax paste increased, mean WVP, E, and TSM values of SPI-sorghum-wax-paste composite films decreased and were lower than those of control SPI films. Mean TS values were lower than the control upon addition of 5 and 10% wax paste; however, TS values increased at 15 and 20% was concentrations. Although no differences in components of sorghum wax were observed between paste extracted with ethanol and wax extracted with hexane, paste extracted with ethanol was miscible with the filmforming solution. SPI-sorghum wax paste films had better water barrier and physical properties compared to control films.     

PVAc乳胶/改性大豆分离蛋白共混胶黏剂的制备及性能

针对大豆蛋白胶黏剂耐水性差的缺点,用尿素初步改性大豆分离蛋白（SPI）,然后与白乳胶（PVAc）共混合成了共混改性大豆分离蛋白胶黏剂。采用正交实验方法考察了大豆蛋白胶与白乳胶质量比、共混时间、交联剂质量分数、交联时间对大豆蛋白胶黏剂剪切粘接强度的影响,确定了优化配比及制备工艺条件,并在此基础上采用正交试验优化了热压参数。结果表明：大豆蛋白胶与白乳胶质量比10∶1,共混时间1h,交联剂质量分数1.0%,交联时间1.5h,热压温度120℃,热压压强1.2MPa,热压时间2min/mm,涂胶量250g/m2时,测得胶黏剂的干态剪切粘接强度为2.01MPa,按照Ⅰ类胶合板标准测得湿态剪切粘接强度为1.04MPa,并对优化配方进行了结构与性能分析。     

Functional properties of extruded-expelled soybean flours from value-enhanced soybeans

The functional properties (protein solubility, emulsification characteristics, foaming characteristics, water- and fatbinding capacities) of extruded-expelled (EE) soy flours originating from six varieties of value-enhanced soybeans (high-sucrose, high-cysteine, low-linolenic, low-saturated FA, high-oleic, and lipoxygenase-null) and two commodity soybeans were determined. The soy flours varied in protein disperisibility index (PDI) and residual oil (RO), with PDI values ranging from 32 to 50% and RO values ranging from 7.0 to 11.7%. Protein solubility was reduced at pH values near the isoelectric region and was higher at both low and high pH. There were no significant differences for water-holding capacity, fat-binding capacity, emulsification activity, or emulsification stability. Only the high-oleic soy flour had significantly lower emulsification capacity. In general, the PDI and RO values of EE soy flours originating from value-enhanced and commodity soybeans had the greatest influence on protein functionality. The genetic modifications largely did not affect functional properties.     

Effect of lipids on soy protein isolate solubility

Reduced-lipid soy protein isolate (SPI), prepared from soy flour treated so that most of the polar lipids have been removed, exhibited an increase in protein solubility of 50% over that of the control SPI prepared from hexane-defatted flour. Adding lipids from a commercial SPI during processing of reduced-lipid SPI decreased SPI solubility by 46%. The 19% decreased solubility caused by the lipids (primarily phospholipids) was largely recovered by treating the protein with a reducing agent (2-mercaptoethanol). The balance of protein insolubility, caused by the lipids, was attributed to a smaller lipid fraction (approximately 5% of the total lipids). Adding lipids during SPI processing contributed to both the formation of oxidized protein sulfhydryls, incapable of being reduced by 2-mercaptoethanol, and to oxidative deterioration of protein as determined by protein carbonyl contents.     

Hydrogel films and microcapsules based on soy protein isolate combined with alginate

Alginate hydrogels are combined with soy protein isolate (SPI), a plant derived protein with low immunogenicity, appropriate biodegradability and low cost, to produce biocompatible films, and microcapsules. The cell–material interaction is assessed through the use of mouse embryotic fibroblast cells (MEF cells) on films, and the results illustrate that the alginate/SPI hydrogel films support cell attachment, spreading, and proliferation. Cell biology results combined with degradation studies suggest that such hydrogels are promising biomaterials for soft tissue regeneration or as wound dressing materials. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44358.     

Mechanism of physical modification of insoluble soy protein concentrate

The mechanism for solubilization of alcohol-leached soy protein concentrate (ALSPC) by physical modification was studied from the standpoint of molecular interactions, which are related to the differences in protein solubility under different conditions. The low solubility of ALSPC is caused by both noncovalent and covalent forces, but the noncovalent forces do not affect the solubility of modified soy protein concentrate (MSPC). Gel filtration shows that the major constituents of soluble protein from ALSPC and MSPC are protein molecules and protein aggregates, respectively. Physical modification promotes the formation of aggregates that are readily soluble in buffer. Fluorescence spectroscopy further proved that the hydrophobic groups are located in the interior of the aggregates. The reason for the formation of soluble protein aggregates during physical modification of ALSPC is discussed.     

Properties of molded soy protein isolate plastics

Thermal property of soy protein isolates (SPI) was studied with differential scanning calorimetry and thermogravimetric analysis. The weight loss of pure SPI is about 300°C. The glass transition temperature (T_g) is above 200°C. The best molding temperature of glycerin plasticized SPI plastics were then given. It is between 125 and 140°C. Subsequently the special property of molded SPI plastics was investigated. Results show that the atmosphere humidity affects the mechanical property and thermal property of SPI plastics. With the increasing humidity, the tensile strength decreases. While the elongation at breakage and peak area of the differential scanning calorimetry curve increases. At high temperature even at 140°C the molding temperature SPI plastics still have tensile strength though it decreases with the increasing test temperature while elongation at breakage increases. Dynamic mechanic thermal analysis test show that the storage modulus decreases with the rising temperature. The mechanical loss peak appears at lower temperature with the increasing amount of glycerin content. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Functional properties of hydrothermally cooked soy protein products

The effects of hydrothermal cooking on the functional properties of defatted soy flour, aqueous alcohol washed soy protein concentrate, and soy protein isolate were determined in samples that were treated at 154°C by infusing steam under pressure for 11, 19, 30, and 42 s, and then spray dried. Hydrothermal cooking increased the nitrogen solubility index (NSI) of the concentrate from 15 to 56% and altered the solubility profile from a flat profile to one more typical of native soy protein. Hydrothermal cooking also improved foaming and emulsifying properties of the concentrate. For isolate, hydrothermal cooking also improved NSI and foaming and emulsifying properties, although the improvements were less dramatic than with concentrate. NSI and emulsifying properties of the flour were improved by some processing conditions, but foaming properties were not improved by hydrothermal cooking. Dramatically increased protein solubility of concentrate and modestly improved protein solubilities of flour and isolate by hydrothermal cooking, which will also inactivate trypsin inhibitors and microorganisms, have considerable practical significance to protein ingredient manufacturers and those who use these ingredients in foods and industrial products.     

Enzymatic hydrolysis and fermentation of soy flour to produce ethanol and soy protein concentrate with increased polyphenols

There is a need to effectively concentrate soy protein from defatted soy flour (DSF) while simultaneously valorizing the carbohydrate-rich byproduct, which would otherwise be a waste. This study aims to evaluate a process developed to produce soy protein concentrates (SPC) by substantially hydrolyzing carbohydrates from DSF with the help of enzymes into water-soluble saccharides and monomeric sugars, which were simultaneously utilized by Saccharomyces cerevisiae for fermentation into ethanol. The enzyme mixture consisted of cellulase, pectinase, and $\mathrm{\alpha }$-galactosidase blend. The effect of process time on SPC, overall protein recovery, carbohydrate hydrolysis, yeast growth, ethanol concentration, and total polyphenol concentration (TPC) of SPC and hydrolysate was evaluated. Control and enzymes-only (EO) systems were maintained in conjunction with the enzymes + yeast (EY) system to individually assess the impact of isoelectric precipitation of soy proteins and enzymatic hydrolysis of carbohydrates without yeasts. After 12.25 h of EY process, 100 g of dry DSF produced 68.45 g dry SPC containing $72.23\pm 0.25$% protein and 384 ml hydrolysate containing $9.76\pm 0.05$ mg/ml ethanol. Flatulence-causing raffinose-series-oligosaccharides (RSOs) were completely hydrolyzed. Soluble carbohydrates in the EY treatment were consistently lower than in the control and EO treatment. TPC of SPC prepared by EY treatment increased by 2.5 times compared to the control. Thus, this novel process successfully produced a high-protein SPC with hydrolyzed RSOs, lower insoluble carbohydrates, high TPC, and a coproduct ethanol.     

Miscibility,morphology, structure,and properties of porous cellulose–soy protein isolate hybrid hydrogels

Porous hybrid hydrogels were fabricated by mixing cellulose (CEL) and soy protein isolate (SPI) solutions, followed by crosslinking with epichlorohydrin. Their miscibility, morphology, structure, and properties were investigated by wide‐angle X‐ray diffraction, thermogravimetric analysis, scanning electron microscopy, dynamic mechanical analysis, rheological measurement, and swelling tests. The results show that CEL performed as a “scaffold” of pore walls and contributed to the good mechanical properties, while SPI performed the role of an “extender” of pore size and was responsible for the high water absorbency. The incorporation of CEL (stiff chains) and SPI (hydrophilic groups) in the hybrid hydrogel constructed the porous structure. This work provides a method for the fabrication of hydrogels with porous structure through the combination of a stiff material as a “scaffold” and a hydrophilic material as an “extender.” © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43853.     

Effect of xanthan gum on enhancing the foaming properties of soy protein isolate

The foaming properties of soy protein isolate (SPI) in the presence of xanthan gum (XG) were investigated. The XG solution alone did not exhibit any foaming ability. The optimal foaming properties were obtained from the SPI-XG dispersion that contained 0.1% SPI and 0.2% XG. This SPI-XG dispersion gave higher foaming capacity than that of SPI or egg white (P<0.05). The foam stability of SPI-XG dispersion was nine times higher than that of SPI and egg white (P<0.05). The SPI-XG foams were stable over wide ranges of ionic strength (0.1 to 1.0 M NaCl) and pH (4.5 to 9.0), and when heated (85°C, 1 h).     

Foaming and emulsifying properties of soy protein isolate and hydrolysates in skin and hair care products

There is a growing market for formulating proteins into a wide variety of products including laundry detergents, bath products, shampoos, and skin cleansers. Soy protein isolate (SPI), soy protein hydrolysate A (SPHA) from papainmodified SPI, and hydrolysate B from papain- and proteasemodified SPI were used in blends with three major detergents, sodium dodecyl sulfate (SDS), sodium laureth sulfate (SLS), and disodium lauryl sulfosuccinate (DSLSS). SPHA was used to partially replace these detergents in bath soap, conditioning shampoo, and cream hand cleanser. The effectiveness of SPI, SPHA, or SPHB blends with the three detergents and their influence in prototype products on foaming and emulsifying properties were investigated. At a blending ratio of 75% detergents and 25% proteins (75∶25), the foaming capacities (FC) were the same as detergents alone without adding proteins (100∶0); at 50∶50 blending ratio, FC values were not significantly reduced for blends with SDS and SLS; and at 25∶75 ratio the FC values were significantly lower, especially for blends with DSLSS. When replacing up to 100% of the major detergents in the skin and hair care products with SPHA, FC values remained almost unchanged except for hand cleanser FC values, which were lower at higher protein content (75 and 100%). In contrast with FC performance, emulsion stability (ES) values for all products increased with increasing soy protein content. Furthermore, FC and ES values for detergents blended with SPHA or SPHB were not significantly different from each other, but these values were always higher than those for detergents blended with SPI. Products in which soy protein or soy protein hydrolysates were used to partially replace detergents not only retained excellent foaming properties but also exhibited enhanced emulsifying properties. These results indicate that modified soy proteins may be used in laundry and cosmetic products to fulfill market demand.     

Physical and mechanical properties of soy protein-based plastic foams

Flexible plastic foams using soy protein isolate (SPI), soy protein concentrate (SPC), and defatted soy flour (DFS) were produced by interacting proteins with glycerol-propylene oxide polyether triol (polyol), surfactant, triethanolamine (crosslinking agents), tertiary amine (catalyst), and water (blowing agent). The density, compressive stress, resilience, and dimensional stability of foams with SPI, SPC, and DFS increased as the initial concentration of soy protein increased. The foam density increased with increasing weight percentage of SPI, SPC, and DFS. The resilience values of SPI containing foam increased with the increasing addition of SPI up to a maximum 30% SPI addition. An increase in SPI up to 20% caused an increase in the compressive stress (225 kPa) in comparison to control polyurethane foam (187 kPa). The control foam and foam containing 20% DFS had a similar load-deformation relationship. The foam containing 20% SPI and SPC also exhibited a similar shape, but with a higher compressive stress. The compressive stress of all foams was steeply increased after 55% strain, since the foams completely collapsed upon compression.     

Twin-screw extrusion texturization of extruded-expelled soybean flour

Texturized soy proteins (TSP) have been produced from hexane-extracted soy flours having a narrow range of characteristics. The objective of this study was to determine the influence of protein dispersibility index (PDI) and residual oil content on extrusion texturization of partially defatted soy flours produced by extruding-expelling (E-E). Ten E-E processed soy flours having residual oil contents and PDI values of 5.5–12.7% and 35.3–69.1%, respectively, were texturized using a twin-screw extruder. Water-holding capacities were greater for TSP prepared from E-E processed soy flours with lower residual oil contents. Bulk densities were significantly lower for TSP prepared from E-E processed soy flours compared with a commercial product made from hexane-extracted soy flour. The texture characteristics of extended ground beef patties containing texturized E-E processed soy flour were similar to that of 19% fat ground beef. Flavor acceptability was directly correlated (R=0.761) with residual oil content of the E-E processed soy flours. However, lower residual oil and higher PDI flours exhibited better texturization and extrudate qualities.     

Blends of polylactic acid and arylated soy protein isolate with triacetine as plasticiser

Abstract

Blends of polylactic acid (PLA) and arylated soy protein isolate (ASPI) were successfully prepared by the extrusion process followed by injection moulding. To improve the interfacial adhesion between PLA and ASPI powder, mandelic acid as an amphiphilic additive was incorporated. Rheological and thermal characterisations of PLA/ASPI blends were performed on rheometer, differential scanning calorimeter and thermogravimetric analyser. Thermomechanical characterisation of PLA/ASPI blends was carried out on a dynamic mechanical analyser. Tensile and flexural modulus of PLA/ASPI blends increased compared to neat PLA. Different amounts (5–15 wt-% wrt PLA/ASPI blends) of plasticiser was added to PLA/ASPI blends containing 2·5 wt-% of ASPI. Results indicated that at 10 wt-% of plasticiser, PLA/ASPI blends showed maximum tensile strength of ～8·8 MPa as well as appreciable elongation at break. Morphological studies of PLA/ASPI blends at different amounts of plasticiser were also carried out by scanning electron microscope.