The Experts below are selected from a list of 267 Experts worldwide ranked by ideXlab platform
Georges Daufin - One of the best experts on this subject based on the ideXlab platform.
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Whey protein fractionation: Isoelectric Precipitation of α-lactalbumin under gentle heat treatment
Biotechnology and bioengineering, 1997Co-Authors: C. Bramaud, Pierre Aimar, Georges DaufinAbstract:The selective Precipitation of alpha-lactalbumin (alpha-LA) at a pH around its Isoelectric point (4.2) under heat treatment is the basis for a fractionation process of whey proteins. In these conditions, beta-lactoglobulin remains soluble, whereas bovine serum albumin and immunoglobulins co-precipitate. Knowledge of the mechanism governing the alpha-LA Precipitation influences the choice of operating conditions and enables optimization of the fractionation process. alpha-LA is a calcium metallo-protein and its Isoelectric Precipitation is governed by the protein-calcium complexation equilibrium. Citrate, a sequestrant of calcium, decreases the free calcium concentration and displaces the Precipitation phenomenon to a lower temperature range. A study of the effect of citrate on the Precipitation phenomena of whey proteins is presented. Whatever the citrate content, Precipitation curves for bovine serum albumin (BSA) and alpha-LA intersect at a temperature around 45 degrees C. For a temperature of heat treatment lower than 40 degrees C, a selective enrichment in alpha-LA of the precipitated phase is observed. As addition of citrate leads to high alpha-LA precipitated fractions at a temperature around 35 degrees C, the Precipitation step may be performed at this temperature. It results in a reduced heat denaturation of whey proteins and in a higher alpha-LA purity in the precipitated fraction. (c) 1997 John Wiley & Sons, Inc. Biotechnol Bioeng 56: 391-397, 1997.
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Thermal Isoelectric Precipitation of α-lactalbumin from a whey protein concentrate: Influence of protein–calcium complexation
Biotechnology and bioengineering, 1995Co-Authors: C. Bramaud, Pierre Aimar, Georges DaufinAbstract:The selective Precipitation of α-lactalbumin (α-LA) at a pH around its Isoelectric point (4.2) under heat treatment is the basis for a fractionation process of whey proteins. As Precipitation is a phenomenon dependent on the protein hydrophobicity, and as the release of the tightly bound calcium occurring at pH around 4 modifies the α-LA hydrophobicity, the specific role of calcium on Isoelectric Precipitation is investigated. A study of the extent of α-LA Precipitation in a whey protein concentrate under various operating conditions of pH, temperature, protein concentration, and calcium content is presented. We propose a mechanism for this phenomenon as a combination of a complexation equilibrium and of an irreversible Precipitation, to account for the influence of temperature, α-LA concentration total ionic content, and calcium concentration, and also to estimate the complexation equilibrium constant. © 1995 John Wiley & Sons, Inc.
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thermal Isoelectric Precipitation of α lactalbumin from a whey protein concentrate influence of protein calcium complexation
Biotechnology and Bioengineering, 1995Co-Authors: C. Bramaud, Pierre Aimar, Georges DaufinAbstract:The selective Precipitation of α-lactalbumin (α-LA) at a pH around its Isoelectric point (4.2) under heat treatment is the basis for a fractionation process of whey proteins. As Precipitation is a phenomenon dependent on the protein hydrophobicity, and as the release of the tightly bound calcium occurring at pH around 4 modifies the α-LA hydrophobicity, the specific role of calcium on Isoelectric Precipitation is investigated. A study of the extent of α-LA Precipitation in a whey protein concentrate under various operating conditions of pH, temperature, protein concentration, and calcium content is presented. We propose a mechanism for this phenomenon as a combination of a complexation equilibrium and of an irreversible Precipitation, to account for the influence of temperature, α-LA concentration total ionic content, and calcium concentration, and also to estimate the complexation equilibrium constant. © 1995 John Wiley & Sons, Inc.
María Agustina Reinheimer - One of the best experts on this subject based on the ideXlab platform.
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Performance evaluation of protein recovery from Argentinian soybean extruded-expelled meals under different operating conditions
Journal of Food Engineering, 2020Co-Authors: Cecilia Accoroni, Ezequiel Godoy, María Agustina ReinheimerAbstract:Abstract The soybean extruded-expelled (EE) meals are the byproduct of the process commonly used by small or medium-sized Argentinian companies for obtaining soy oil. In this work, the performance of the pH-shifting process for obtaining a protein product from the EE meals was evaluated as a strategy for on-site value-adding. The EE meals were subjected to the proposed pH-shifting process under different operating parameters at the alkaline extraction stage (2 and 3 cycles at 55, 60 and 65 °C with and without sodium sulfite) and Isoelectric Precipitation stage (0 °C and 20 °C with hydrochloric and phosphoric acids), which constitute the controlling steps in an industrial scaling of the process. The pH-shifting process consisting of 3 alkaline extraction cycles at 60 °C followed by Isoelectric Precipitation at low temperature using hydrochloric acid was found to be well suited for obtaining a final product with a protein content upwards of 75%.
Sohrab Rohani - One of the best experts on this subject based on the ideXlab platform.
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Isoelectric Precipitation of sunflower protein in an msmpr precipitator modelling of psd with aggregation
Chemical Engineering Science, 1996Co-Authors: Matheo Raphael, Sohrab RohaniAbstract:Abstract Isoelectric Precipitation of sunflower protein was carried out in a 273 ml MSMPR precipitator. Experimental results showed a bimodal particle-size distribution (PSD) of protein particles when the solids concentration or the mean residence time was low. Increasing the solids concentration and the mean residence time transformed the bimodal PSD to a unimodal PSD. Protein particle growth by turbulent collision mechanism and breakage by shear mechanism were modelled using an approach similar to Glatz et al. A.I.Ch.E. J.32, 1196–1204 (1986). The model results showed that the breakage of large aggregates results in the birth of two daughter fragments. Also at high solids concentrations the particle growth rate was linear with respect to particle size. At low solids concentrations the growth rate constant was larger than the breakage rate constant and vice versa at high solids concentrations.
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Isoelectric Precipitation of sunflower protein in a tubular precipitator
Canadian Journal of Chemical Engineering, 1995Co-Authors: Matheo Raphael, Sohrab Rohani, F SosulskiAbstract:Isoelectric Precipitation of sunflower protein was carried out in a 10-m long, 6-mm internal diameter glass tubular precipitator. The effects of feed flow rate, protein concentration in the feed stream, and volumetric feed ratio of precipitant (HCl aqueous solution) to protein solution on solid protein recovery and particle size distribution were studied. The dispersion range of the tubular precipitator was modelled to predict the experimental results. Calculated initial growth rates of protein particles were found to: increase with increases in feed flow rate and protein concentration in the feed stream, and decrease with increases in volumetric feed ratio. On a realise la Precipitation isoelectrique de la proteine de tournesol dans un precipitateur tubulaire de verre de 6 mm de diametre interne et de 10 m de long. On a etudie les effets du debit d'alimentation, de la concentration en proteine dans le courant d'alimentation ainsi que du rapport d'alimentation volumetrique entre le precipitant (solution de HCl aqueuse) et la solution de proteine sur la recuperation de proteine solide et la distribution de taille des particules. La gamme de dispersion du precipitateur tubulaire a ete modelisee pour predire les resultats experimentaux. On a trouve, d'une part, que les vitesses de croissance initiales calculees des particules de proteine augmentaient avec le debit d'alimentation et la concentration en proteine dans le courant d'alimentation et, d'autre part, qu'elles diminuaient avec l'augmentation du rapport d'alimentation volumetrique.
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aggregation and Precipitation kinetics of canola protein by Isoelectric Precipitation
Canadian Journal of Chemical Engineering, 1993Co-Authors: Sohrab Rohani, M ChenAbstract:Kinetics of aggregation, nucleation and growth of canola protein particles were developed in a 100 mL mixed-suspension mixed-product removal precipitator (MSMPRP) using Isoelectric Precipitation with HCI at pH 4.2. Protein yield in terms of total nitrogen was measured by Kjeldahl system. The size distribution of protein aggregates was determined by a Coulter counter. The effects of pH, protein concentration driving force, mean residence time, agitation rate, ionic strength of the solution, and the operating temperature on the size distribution and yield of protein particles were investigated. Population balance on the protein particles was used to derive empirical correlations for the index of aggregation, nucleation rate of primary particles and growth rate of protein aggregates. On a etudie la cinettique d'aggregation, de nucleation et de croissance de particules de proteine de canola dans un precipitateur de retrait a suspension et a produit mixtes de 100 mL, en ayant recours a la Precipitation isoelectrique avec du HCI a un pH de 4,2. Le rendement des proteines en termes d'azote total a ete mesure au moyen du systeme Kjeldahl. On a determine la distribution de taille des aggregats de proteines grâce a un compteur Coulter. On a etudie les effets du pH, de la force motrice de concentration en proteines, du temps de sejour moyen, de la vitesse d'agitation, de la force ionique de la solution et de la temperature de fonctionnement sur la distribution de taille et le rendement des particules de proteine. On a utilise un bilan de population sur les particules de proteine pour etablir des correlations empiriques concernant I'indice d'aggregation, la vitesse de nucleation des particules primaires et le taux de croissance des aggregats de proteine.
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Recovery of canola meal proteins by Precipitation.
Biotechnology and Bioengineering, 1992Co-Authors: M Chen, Sohrab RohaniAbstract:: Recovery of rapeseed proteins from defatted canola meal by Precipitation was investigated. The ability of different precipitating agents, such as sodium hexametaphosphate (HMP), carboxymethylcellulose (CMC), ammonium sulphate, and Isoelectric Precipitation using HCl, were evaluated based on the yield and mean size of protein aggregates. Almost 94% of dissolved protein was precipitated in the presence of 2.7 M ammonium sulphate, while the largest mean protein particle size (32 microm) was obtained in the presence of HMP at pH 3.3.
G. Doxastakis - One of the best experts on this subject based on the ideXlab platform.
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Emulsifying and foaming properties of Phaseolus vulgaris and coccineus proteins
Food Chemistry, 2006Co-Authors: Eleousa A. Makri, G. DoxastakisAbstract:Abstract Protein isolates from two Phaseolus cultivars, common bean ( Phaseolus vulgaris L.) and scarlet runner bean ( Phaseolus coccineus L.), were prepared by wet extraction methods (Isoelectric Precipitation – 4000 rpm, ultrafiltration, extraction with NaCl 2%, and Isoelectric Precipitation – 9900 rpm). The protein isolates were characterized by sodium dodecyl sulfate–polyacrylamide gel electrophoresis and then evaluated for their solubility. The emulsion stability of emulsions produced at pH 7.0 and 5.5 with 1% or 2% or 3% w/v protein isolate was evaluated by average droplet size diameter, viscosity and creaming measurements. Emulsions with 1% protein content were unstable through storage. Emulsions with 3% w/v protein isolate concentration, extracted by ultrafiltration at pH 5.5 from both cultivars, were flocculated; this was more pronounced for coccineus isolates. The foaming properties, for the respective foams, were investigated. Foams with 1% w/v protein showed little foaming ability Ultrafiltration isolates produced more foam, which was especially stable at pH 5.5.
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Emulsifying and foaming properties of amaranth seed protein isolates.
Colloids and surfaces. B Biointerfaces, 2001Co-Authors: A Fidantsi, G. DoxastakisAbstract:The emulsifying and foaming properties of amaranth seed protein isolates prepared by wet extraction methods, such as Isoelectric Precipitation and dialysis, were investigated. The various isolates differ from each other in many ways. The isolate prepared by Isoelectric Precipitation mainly contains the globulin but not the albumin fraction and a considerable amount of polysaccharides, while the other isolate prepared by the dialysis method contains all the globulin and albumin fractions. The protein-polysaccharide complexes enhance emulsion stability due to steric repulsion effects. Measurements of the emulsion stability show that the studied protein isolates act as effective stabilizing agents. Foam expansion is dominated by the surface activity and availability of protein in the solution, while foam stability is determined by the properties of the interfacial layer. The results show that amaranth protein isolates act as an effective foaming agent. Both foaming properties intensified from the presence of protein-polysaccharide complexes.
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physical characterization of thermally induced networks of lupin protein isolates prepared by Isoelectric Precipitation and dialysis
International Journal of Food Science and Technology, 1999Co-Authors: Antonios Kiosseoglou, G. Doxastakis, Stefan Alevisopoulos, Stefan KasapisAbstract:Summary Protein isolates of Lupinus albus were obtained from full fat and defatted lupin flour using Isoelectric Precipitation or dialysis. Calorimetric tests demonstrated that the main protein fractions of the isolates denature well below 100 °C. Mechanical spectra of isolate dispersions obtained at 80 °C indicated the formation of a ‘pseudogel’ whose cohesion increased during cooling to 10 °C. Subsequent heating to 90 °C encouraged extensive formation of disulphide bonds as it produced gels that were insoluble in sodium dodecyl sulphate and urea solutions. Dialysis produced isolates of lower gelling concentrations, which also formed networks of a stronger relative elastic character. The presence of NaCl at concentrations up to 0.5 m had a reinforcing effect on networks. Protein over-aggregation caused the opposite effect at higher salt levels. Finally, a comparison with results in the literature on soybean protein gelation suggested similar denaturation temperatures and a common pattern of structure formation for the two legume proteins.
C. Bramaud - One of the best experts on this subject based on the ideXlab platform.
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Whey protein fractionation: Isoelectric Precipitation of α-lactalbumin under gentle heat treatment
Biotechnology and bioengineering, 1997Co-Authors: C. Bramaud, Pierre Aimar, Georges DaufinAbstract:The selective Precipitation of alpha-lactalbumin (alpha-LA) at a pH around its Isoelectric point (4.2) under heat treatment is the basis for a fractionation process of whey proteins. In these conditions, beta-lactoglobulin remains soluble, whereas bovine serum albumin and immunoglobulins co-precipitate. Knowledge of the mechanism governing the alpha-LA Precipitation influences the choice of operating conditions and enables optimization of the fractionation process. alpha-LA is a calcium metallo-protein and its Isoelectric Precipitation is governed by the protein-calcium complexation equilibrium. Citrate, a sequestrant of calcium, decreases the free calcium concentration and displaces the Precipitation phenomenon to a lower temperature range. A study of the effect of citrate on the Precipitation phenomena of whey proteins is presented. Whatever the citrate content, Precipitation curves for bovine serum albumin (BSA) and alpha-LA intersect at a temperature around 45 degrees C. For a temperature of heat treatment lower than 40 degrees C, a selective enrichment in alpha-LA of the precipitated phase is observed. As addition of citrate leads to high alpha-LA precipitated fractions at a temperature around 35 degrees C, the Precipitation step may be performed at this temperature. It results in a reduced heat denaturation of whey proteins and in a higher alpha-LA purity in the precipitated fraction. (c) 1997 John Wiley & Sons, Inc. Biotechnol Bioeng 56: 391-397, 1997.
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Thermal Isoelectric Precipitation of α-lactalbumin from a whey protein concentrate: Influence of protein–calcium complexation
Biotechnology and bioengineering, 1995Co-Authors: C. Bramaud, Pierre Aimar, Georges DaufinAbstract:The selective Precipitation of α-lactalbumin (α-LA) at a pH around its Isoelectric point (4.2) under heat treatment is the basis for a fractionation process of whey proteins. As Precipitation is a phenomenon dependent on the protein hydrophobicity, and as the release of the tightly bound calcium occurring at pH around 4 modifies the α-LA hydrophobicity, the specific role of calcium on Isoelectric Precipitation is investigated. A study of the extent of α-LA Precipitation in a whey protein concentrate under various operating conditions of pH, temperature, protein concentration, and calcium content is presented. We propose a mechanism for this phenomenon as a combination of a complexation equilibrium and of an irreversible Precipitation, to account for the influence of temperature, α-LA concentration total ionic content, and calcium concentration, and also to estimate the complexation equilibrium constant. © 1995 John Wiley & Sons, Inc.
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thermal Isoelectric Precipitation of α lactalbumin from a whey protein concentrate influence of protein calcium complexation
Biotechnology and Bioengineering, 1995Co-Authors: C. Bramaud, Pierre Aimar, Georges DaufinAbstract:The selective Precipitation of α-lactalbumin (α-LA) at a pH around its Isoelectric point (4.2) under heat treatment is the basis for a fractionation process of whey proteins. As Precipitation is a phenomenon dependent on the protein hydrophobicity, and as the release of the tightly bound calcium occurring at pH around 4 modifies the α-LA hydrophobicity, the specific role of calcium on Isoelectric Precipitation is investigated. A study of the extent of α-LA Precipitation in a whey protein concentrate under various operating conditions of pH, temperature, protein concentration, and calcium content is presented. We propose a mechanism for this phenomenon as a combination of a complexation equilibrium and of an irreversible Precipitation, to account for the influence of temperature, α-LA concentration total ionic content, and calcium concentration, and also to estimate the complexation equilibrium constant. © 1995 John Wiley & Sons, Inc.
