Production of soy protein concentrates/isolates: traditional and membrane technologies (2025)

Characterization of low-phytate soy protein isolates produced by membrane technologies

Innovative Food Science & Emerging Technologies, 2010

Soy protein isolates (SPI) produced by combining electro-acidification and tangential ultrafiltration/ diafiltration (UF/DF) (pH 6), were compared in terms of composition and proteins solubility with isolates produced by UF/DF (pH 9) and isoelectric precipitation (pH 4.5). Mineral and phosphorus (phytic acid) removal was enhanced for the SPI pH 6. Whey-like proteins (M.W. b 66 kDa) were also found in higher concentration for the SPI produced by membrane technologies. This difference in composition resulted in improved solubility characteristics for the SPI pH 6 by as high as 25% and 60%, when compared to the SPI pH 4.5 and SPI pH 9, respectively. Improvement in solubility was most important between pH 2 and 4.5. The quantity of H + ions added to the soy protein extract (SPE) and SPI to reduce the pH from 9 to 4.5, during solubility measurement, was related to the degree of proteins aggregation, as determined by size-exclusion high-performance liquid chromatography, and at a lesser extent to their phytic acid content. For the pH range of 4.5 to 2, the degree of proteins aggregation alone determines the quantity of H + ions added. Industrial relevance: Soy protein production is one of the major agricultural sectors of significant importance to North America and soy proteins represent 69% of global plant protein consumption in the world. Soy protein concentrates and isolates are produced at the industrial scale by isoelectric precipitation. This process has a high productivity, however, it also generates large volumes of effluent. The final products also have significant contents of minerals and of phytic acid, the latter of which is well known to decrease the proteins and minerals adsorption in the intestine. We were the first group to combine bipolar membrane electrodialysis (BMED) and ultrafiltration (UF) (dead-end) for the production of soy protein concentrates . The new approach resulted in a significant decrease of the volumes of effluent due to the use of BMED to adjust the pH of the extract prior to UF and by improving the protein washing step using diafiltration (DF). It was also shown that for the pH range 6-9, minerals and phytic acid removal was improved with a decrease in pH. In this work, we present the characteristics of a soy protein isolate with a low phytic acid/protein ratio (SPI pH 6) produced by BMED and tangential flow UF/DF applying an optimal VCR5, re-VCR 5 sequence at pH 6. The SPI pH 6 shows an improved solubility by as high as 25% and 60%, when compared to an isolate produced by isoelectric precipitation at pH 4.5 and to one produced by UF/DF at pH 9, respectively. Improvement in solubility was most important between pH 2 and 4.5 indicating that this isolate could be considered as a valuable ingredient for the formulation of fruit juice beverages or power juices, considering that the pH of these liquid food products is around 3.5.

Effect of electro-acidification treatment and ionic environment on soy protein extract particle size distribution and ultrafiltration permeate flux

Journal of Membrane Science, 2004

The present study emerges from the development of a process aimed at integrating electro-acidification and ultrafiltration for the production of soy protein isolate. It was observed that electro-acidification treatments, which change the pH and the salt content of the soy protein extracts, influence the permeate flux during dead-end ultrafiltration. The effects of electro-acidification treatments on the soy protein extracts were quantified through experimental measurement of particle size distribution, molecular weight profiles, protein solubility and particle volume fraction. A criterion for the particle deposition into the concentrated layer or at the membrane surface was obtained from the analysis of the net force along the direction of permeation. The particle size distribution and the criterion for the particle deposition were used to obtain information about the particle transport into the concentrated layer, as a function of the pH and salt content, and were related to the global resistance, which is mainly attributable to both concentrated layer and cake layer together. For soy protein extracts reconstituted in double distilled water or in 0.12 M KCl, it was found that particle size distribution vary with pH and salt content and this was mainly attributable to the aggregation-disaggregation behavior of the different proteins fraction. For the soy protein extracts reconstituted in double distilled water, the mean particle size, the particle transport into the concentrated layer and the global resistance were maximum at pH 7, slightly lower at pH 6 and minimum at pH 9. This resulted in minimum permeate flux at pH 7, slightly higher at pH 6 and maximum at pH 9. For the soy protein extracts reconstituted in 0.12 M KCl, all three parameters increased with a decrease of pH. This resulted in a permeate flux decrease with a decrease of pH. Crown

Production of low-phytate soy protein isolate by membrane technologies: Impact of salt addition to the extract on the purification process

Innovative Food Science & Emerging Technologies, 2011

Previously, the advantages of combining electrodialysis with bipolar membranes (EDBM) to acidify a soy protein extract to pH 6 with ultrafiltration/diafiltration (UF/DF) using a 100 kDa membrane to produce a soy protein isolate (SPI) with low phytic acid to protein ratio were demonstrated. However, some limitations related to the fouling of ED spacers by precipitated proteins and to the flux decline during UF/DF at pH 6 were observed. Therefore the purpose of this work was to study the impact of adding KCl (0.12 M or 0.24 M) to the starting extract on the efficiency of both processes and on the solubility of the resulting isolates. Results indicated that adding KCl to the initial extract increased the productivity of EDBM by approximately two times and reduced proportionally its energy requirement. This was in large part due to the prevention of ED spacer fouling. Permeate flux during UF/DF was improved by as much as 20% when compared to the flux measured for the purification of pH 6 extracts without added salt. The phytic acid to protein ratio for pH 6 isolates obtained from the addition of KCl to the initial extract were also found to be lower than for isolates produced at pH 9 or by isoelectric precipitation at pH 4.5, but higher than for the pH 6 isolates obtained without addition of KCl to the initial extract. For the pH range 2-3.5, solubility of these isolates was improved when compared to the one of isolate pH 9, but it was similar to the one of the isolate pH 4.5. Industrial relevance: Production of added-value soy protein isolate is limited by the presence of high amount of phytic acid in the isolate produced by traditional isoelectric precipitation process. We presented previously an approach combining electrodialysis with bipolar membranes (EDBM) with ultrafiltration/diafiltration (UF/DF) for the production of soy protein isolate with low phytic acid to protein ratio and with improved solubility. However, fouling of the electrodialysis spacers by precipitated proteins was observed in the electrodialysis cell which limited practical industrial application of the approach. This problem was solved by the addition of KCl (0.12 M KCl or 0.24 M KCl) to the initial soy protein extract at pH 9 prior to its pH adjustment to 6 by EDBM. It resulted in the improvement of the EDBM productivity by more than 2 times and in a proportional decrease in its energy consumption. Flux during UF/DF at pH 6 was also improved by as much as 20% when KCl was added to the starting extract. In addition, the added KCl was found to be easily removed by UF/DF with the resulting isolates having a final protein content of 94 % which was found similar to the isolate obtained without addition of salt to the starting extract. Although the isolates produced from extracts with added KCl were found to have slightly lower solubility for the pH range of 2 to 3.5 than isolates produced from extract without addition of salt, their solubility was similar or better that for the isolates produced by traditional isoelectric precipitation process and with a lower phytic acid to protein ratio. These isolates could be considered as valuable ingredients for the formulation of fruit juice beverages or power juices, considering that the pH of these liquid food products is around 3.5.

Production of Okara and Soy Protein Concentrates Using Membrane Technology

Journal of Food Science, 2010

Microfiltration (MF) membranes with pore sizes of 200 and 450 nm and ultrafiltration (UF) membranes with molecular weight cut off of 50, 100, and 500 kDa were assessed for their ability to eliminate nonprotein substances from okara protein extract in a laboratory cross-flow membrane system. Both MF and UF improved the protein content of okara extract to a similar extent from approximately 68% to approximately 81% owing to the presence of protein in the feed leading to the formation of dynamic layer controlling the performance rather than the actual pore size of membranes. Although normalized flux in MF-450 (117 LMH/MPa) was close to UF-500 (118 LMH/MPa), the latter was selected based on higher average flux (47 LMH) offering the advantage of reduced processing time. Membrane processing of soy extract improved the protein content from 62% to 85% much closer to the target value. However, the final protein content in okara (approximately 80%) did not reach the target value (90%) owing to the greater presence of soluble fibers that were retained by the membrane. Solubility curve of membrane okara protein concentrate (MOPC) showed lower solubility than soy protein concentrate and a commercial isolate in the entire pH range. However, water absorption and fat-binding capacities of MOPC were either superior or comparable while emulsifying properties were in accordance with its solubility. The results of this study showed that okara protein concentrate (80%) could be produced using membrane technology without loss of any true proteins, thus offering value addition to okara, hitherto underutilized.

Effect of KCl and Soy Protein Concentrations on the Performance of Bipolar Membrane Electroacidification

Journal of Agricultural and Food Chemistry, 1997

The purpose of this study was to evaluate the effects of various combinations of initial concentrations of soy protein concentrate (SPC) (15, 30, and 60 g/L) and KCl (0.06, 0.12, and 0.24 M) on the efficiency of electroacidification technology. This procedure is derived from electrodialysis. Bipolar membrane electroacidification (BMEA) is based on the production of protons by dissociation of water molecules at the interface of membranes called bipolar membranes. The protons generated by this dissociation are able to migrate toward the cathode and acidify a protein solution. At the end of the process at pH 4.5, BMEA yields a protein precipitation of about 93% of total protein in the electroacidified solution. The SPC concentration is the primary factor in the adjustment of the system to optimum energy efficiency, by its intrinsic potassium content. Added salt affects the performance only at low SPC concentration. Increasing the SPC concentration from 15 to 60g/L and the KCl concentration from 0.06 to 0.24 M decreases the relative energy consumption from 2.82 to 0.49 kW/kg of isolate produced. JF970004W X Abstract published in Advance ACS Abstracts, May 15, 1997.

Comparison of Chemical and Bipolar-Membrane Electrochemical Acidification for Precipitation of Soybean Proteins

Journal of Agricultural and Food Chemistry, 1998

We compared chemical and electrochemical acidification in precipitation of soybean proteins, to identify the elements differentiating the two acidification procedures. Chemical acidification and electro-acidification procedures result in differences in 11S precipitation profiles, which would be the consequence of a different solubilization profile of this fraction. At pH 6.0, less of the 11S fraction is precipitated by electro-acidification than by chemical acidification. The conductivity, and consequently the ash content, of the electro-acidified protein solution is decreased while that of the chemically acidified protein solution is increased, depending on the normality of the added HCl.

Electrophoretic, solubility and functional properties of commercial soy protein isolates

Journal of Agricultural and Food Chemistry, 1991

The effect of protein composition and degree of protein denaturation on the solubility, water-imbibing capacity (WIC), viscosity, and gelation capacity of commercial soy protein isolates was studied. It was found that the degree of denaturation may affect protein solubility, but very denatured proteins with high solubility were also detected. Isolates containing completely denatured proteins showed low gelation capacity. This characteristic is closely related to the relative amounts of the 75 and 11s proteins, since 6-7s subunit and basic 11s polypeptide were present in decreased concentrations in the soluble protein fraction. Isolates with a high degree of denaturation and intermediate solubility values presented the maximal WIC. Results confirmed that the apparent viscosity of soy protein dispersions is intimately related to WIC.

Fabrication and Performance of Low-Fouling UF Membranes for the Treatment of Isolated Soy Protein Solutions

Sustainability, 2021

Consumers are becoming more conscious about the need to include functional and nutritional foods in their diet. This has increased the demand for food extracts rich in proteins and peptides with physiological effects that are used within the food and pharmaceutical industries. Among these protein extracts, soy protein and its derivatives are highlighted. Isolated soy protein (ISP) presents a protein content of at least 90%. Wastewaters generated during the production process contain small proteins (8–50 kDa), and it would be desirable to find a recovery treatment for these compounds. Ultrafiltration membranes (UF) are used for the fractionation and concentration of protein solutions. By the appropriate selection of the membrane pore size, larger soy proteins are retained and concentrated while carbohydrates and minerals are mostly recovered in the permeate. The accumulation and concentration of macromolecules in the proximity of the membrane surface generates one of the most importa...

Protein Extraction and Purification of Soybean Flakes and Meals Using a Lime Treatment Followed by Ultrafiltration

Protein extraction and purification by lime treatment and ultrafiltration on soybean flakes and meals is an environmentally friendly process that promises a novel alternative to conventional chemical treatment methods. Protein was extracted from soybean flakes and meals by ionic-strength of lime as alkali treatment. After centrifugation, proteins were purified by ultrafiltration.Lime treatedflakes and meals showed significantly higher level of dissolved solid, protein, and carbohydrate extraction rate than conventional sodium hydroxide or water treatment. Soybean flakes represented a higher extraction rate of protein and carbohydrate than meals. This result may becauseby extensive cell distortion and disruption with cracking, cooking, and flatting which allow lime solutes to easily permeate the cellular matrix. Ultrafiltration substantiallypurified the protein with minor loss of yields, 94.42% and 96.79% for soybean flakes and meals, respectively. Therefore, lime treatment and ultrafiltration is a viable option for extraction and purifying proteins of soybean flakes and meals

Effect of Temperature on the Separation of Soybean 11 S and 7 S Protein Fractions during Bipolar Membrane Electroacidification

Biotechnology Progress, 2000

Québec, Laboratoire des Technologies E Ä lectrochimiques et des E Ä lectrotechnologies, 600, Av. de la Montagne, Shawinigan (Québec), Canada G9N 7N5

Ultrafiltration of industrial waste liquors from the manufacture of soy protein concentrates

Journal of Chemical Technology & Biotechnology, 2006

Protein-containing waste liquors from the manufacture of soy protein concentrates were processed by ultrafiltration to recover soluble protein using three different membranes (with molecular weight cutoffs of 10, 30 and 50 kDa). Operating at 20 • C under reversible conditions, the experimental data of the normalized permeate flux (NPF) obtained at various transmembrane pressures were well described by a model reported in the literature. For each membrane and transmembrane pressure, the values of the parameters involved in the model were calculated. Operating at selected transmembrane pressures, protein rejections of 0.705, 0.747 and 0.637 were determined for the 10, 30 and 50 kDa membranes, respectively. Operation with the 10 kDa membrane at temperatures in the range 30-50 • C and operation with the 30 or 50 kDa membranes at 40 or 50 • C resulted in hysteresis.

Characterization of alkali-modified soy protein concentrate

Acta periodica technologica, 2005

To study the influence of the preparation mode, including mild alkali modification, of soy protein concentrate on soluble protein content and composition, some of its nutritive and functional properties were investigated. Soy protein concentrate prepared by aqueous alcohol leaching was modified in mild alkaline solutions (pH 8.0) at 40, 50 and 60° C for 60 minutes and compared with two principal types of commercial soy protein concentrate. Soluble protein content, composition and properties of soy protein concentrate, as well as their potential use are essentially determined by the preparation mode. Limited mild alkali hydrolysis increased protein solubility by 40-71%, while emulsion stability was increased by 18-56%. Major storage soybean proteins exhibited different stability to alco hol denaturation and mild alkali modification. The most susceptible were acidic -A 3and -A 5 -subunits of glycinin.

Protein Purification to Produce Edible Soybean Protein

2021

This project recommends a design for a soy processing facility to produce soy protein concentrates (SPC), soy oil and soy molasses from dehulled soybeans. Utilities were minimized, wherever possible by evaluating whether streams within the system had the capacity to heat or cool other processes. The plant has a production capacity of 170 MM lb soy protein concentrate/year and will be located in Decatur, IL. The proposed design also yields 114 MM lb soy oil/year and 62 MM lb soy molasses/year. The SPC, soy oil and soy molasses have less than 2 PPM residual solvent concentrations and comply with FDA regulations. The plant is running with an uptime of 80% and economic analysis shows an estimated IRR of 41% with an ROI of 59%

Effect of Limited Hydrolysis on Traditional Soy Protein Concentrate

Sensors, 2006

The influence of limited proteolysis of soy protein concentrate on protein extractability, the composition of the extractable proteins, their emulsifying properties and some nutritional properties were investigated. Traditional concentrate (alcohol leached concentrate) was hydrolyzed using trypsin and pepsin as hydrolytic agents. Significant differences in extractable protein composition between traditional concentrate and their hydrolysates were observed by polyacrylamide gel electrophoresis (PAGE) and by SDS-PAGE. All hydrolysates showed better extractability than the original protein concentrate, whereas significantly better emulsifying properties were noticed at modified concentrates obtained by trypsin induced hydrolysis. These improved properties are the result of two simultaneous processes, dissociation and degradation of insoluble alcohol-induced protein aggregates. Enzyme induced hydrolysis had no influence on trypsin-inibitor activity, and significantly reduced phytic acid content.

Primary treatment of a soybean protein bearing effluent by dissolved air flotation and by sedimentation

Water Research, 1995

The present paper reports on work performed on the recovery of proteins suspended in the effluent of a soybean protein plant. The work involved studies of effluent characterization, protein suspension destabilization, dissolved air flotation (DAF) and gravity settling. The flotation and settling tests were performed both at a batch bench scale and at a continuous plant scale in the actual industrial operation. The soybean proteins, present as a colloidal suspension in the effluent, are dispersed by combined electrostatic repulsion and steric stabilization mechanisms. The destabilization and aggregation of the proteins into high quality flocs were achieved by addition of 200-300 mg/l FeC13, setting the pH at the isoelectric point of the proteins (pH 4.5) and an anionic polyacrylamide polymer (high molecular weight) dosage of 2-3 mg/l. The bench scale tests indicated under these conditions that a solid-liquid separation can be made by both DAF and gravity settling with DAF giving superior results. However, in the industrial plant tests, gravity settling proved generally to give better separation efficiencies. In plant operation the DAF process worked well only if the flocs were sufficiently hydrophobic and resistant to mechanical degradation, which was not always true in the actual operation. The settling process was much less sensitive to feed stock variations.

Thermal and Electrophoretic Behavior, Hydrophobicity, and Some Functional Properties of Acid-Treated Soy Isolates

Journal of Agricultural and Food Chemistry, 1996

In the present work, changes in the structure and functional properties of soy protein isolates caused by mild acid treatment at room temperature were investigated. Different conditions (pH, time, neutralization procedure, and isolate concentration) of acid treatment and consequent salt increase were analyzed. The results obtained show that there is a selective denaturation of 11S protein, which conduces to higher surface hydrophobicity. The solubility of modified isolates decreases with extended storage period of the flour from which they were obtained and with higher isolate concentration during acid treatment. The high water imbibing capacity (WIC) of the resulted insoluble fraction does not produce significant changes in the WIC of the total isolate. The denaturation and dissociation of 11S protein lead to modified isolates with improved capacity to form and to stabilize foams without losing the gel formation capacity.

Some functional properties of fractionated soy protein isolates obtained by microfiltration

Food Hydrocolloids, 2007

Five soy proteins isolate (SPI) fractions were produced using two microfiltration membranes with different pore sizes. Fractionation was carried out on SPI produced by isoelectric precipitation of a crude protein extract. The five fractions were two retentates and two permeates from the two membranes, the fifth fraction was obtained as the retentate on the smaller-pore-sized membrane fed with the permeate from the larger-pore-sized membrane. Solubility, foaming and emulsifying properties of the collected fractionates were investigated. It was observed that in the pH range 3-8 the retentates featured superior solubility compared with permeates. There was no significant difference (p40.01) in solubility between the retentates and SPI at pHX6. Foaming characteristics of the fractions followed the same trend as solubility with regard to foam expansion. There was, however, no particular trend observed with regards to foam stability. Emulsions stabilised by the retentates exhibited higher values (po0.01) of emulsion stability index (ESI) and emulsifying activity index (EAI) than those stabilised with permeates. Sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE) profiles indicated that the fractions exhibiting high functionality in terms of solubility, foaming and emulsifying properties were also richer in 7S globulin soy protein subunits.

The Overview of Food Technology to Process Soy Protein Isolate and Its Application toward Food Industry

World Nutrition Journal

Soy protein isolate (SPI) is the purest form of protein from soybean with minimum protein content of 90%. Due to its high protein content, SPI is commonly used in food processing for improving the quality of food products, including infant formula. The use of SPI in infant formula is mainly designed for infant who cannot tolerate cow’s milk-based formula. This report reviews the benefit of using SPI in soy-based infant formula rather than soymilk from whole soybean itself. It will also review the technology of soy protein isolation which can result SPI for high quality infant formula, including the reducing of unfavourable ingredients which will ensure the safety of soy protein-based infant formula.

Fouling behavior of electroacidified soy protein extracts during cross-flow ultrafiltration using dynamic reversible–irreversible fouling resistances and CFD modeling

Journal of Membrane Science, 2010

The transient membrane fouling during the concentration by cross-flow ultrafiltration of soy protein extracts subjected to electroacidification is examined by combining experimentation with computational fluid dynamics (CFD) modeling. Transient reversible (water removal) and irreversible (chemical removal) membrane fouling resistances, permeate flux, protein concentration and protein concentration dependent viscosity were obtained experimentally. A detailed fouling resistance model to describe the reversible and the irreversible fouling resistances was developed in terms of the microscopic local transient and spatial pressure difference, permeate velocity, protein concentration and initial fouling resistance conditions. This fouling resistance model is used in a boundary condition for the permeate velocity when solving the momentum and protein concentration continuity equations with CFD. The model estimates agree with experimentally measured permeate flux, protein concentration and transient irreversible and reversible fouling resistances. In particular, the model estimated accurately the transient reversible and irreversible fouling resistances, a limitation of most previously published models. The model shows considerable axial variation of the reversible fouling resistance and the protein concentration at the membrane surface which supports the inadequacy of the film theory and the assumptions for constant properties. In contrast, the irreversible fouling resistance remains relatively constant with axial position suggesting protein adsorption.

Milk protein production by a more environmentally sustainable process: bipolar membrane electrodialysis coupled with ultrafiltration

Green Chemistry, 2018

The increased demand for food production to nourish the rapidly growing human population raises serious sustainability issues for the food sector. Indeed, conventional food production lines involve processes having significant environmental burden. Hence, the present study aims to demonstrate an environmentally sustainable way of food production. The milk protein was chosen as a model food ingredient due to its exceptional role in the human diet. The proposed innovative way of milk protein production includes bipolar membrane electrodialysis coupled with ultrafiltration (EDBM-UF). The crucial problem during EDBM-UF of milk, such as different types of membrane fouling, was successfully solved. Moreover, the life cycle assessment of the novel EDBM-UF protein production process was carried out and compared to conventional acid/base process. Additionally, a sensitivity test of electricity supply at different geographical locations of the world was performed since electricity is the main energy source for the EDBM-UF process and it could be derived from different sources (renewable and non-renewable). The assessment results demonstrate that the proposed electromembrane process has significant environmental benefits compared to the conventional process using chemicals independently from the electricity supply mix from all considered geographical locations. Thus, EDBM-UF could become a perspective industrial technology taking into account environmental concerns and promoting the development of healthy human society.