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Milena Corredig - One of the best experts on this subject based on the ideXlab platform.

  • A comparison of the heat stability of fresh Milk Protein Concentrates obtained by microfiltration, ultrafiltration and diafiltration.
    Journal of Dairy Research, 2019
    Co-Authors: Isis Rodrigues Toledo Renhe, Zhengtao Zhao, Milena Corredig
    Abstract:

    : The objective of this work was to evaluate the impact of changes during membrane filtration on the heat stability of Milk Protein Concentrates. Dairy Protein Concentrates have been widely employed in high Protein drinks formulations and their stability to heat treatment is critical to ensure quality of the final product. Pasteurized Milk was concentrated three-fold by membrane filtration, and the ionic composition was modified by addition of water or permeate from filtration (diafiltration). Diafiltration with water did not affect the apparent diameter of the casein micelles, but had a positive effect on heat coagulation time (HCT), which was significantly longer (50 min), compared to the non diafiltered Concentrates (about 30 min). UHT treatments increased the particle size of the casein micelles, as well as the turbidity of retentates. Differences between samples with and without diafiltration were confirmed throughout further analysis of the Protein composition of the unsedimentable fraction, highlighting the importance of soluble Protein composition on the processing functionality of Milk Concentrates.

  • Short communication: Determination of the whey Protein index in Milk Protein Concentrates.
    Journal of Dairy Science, 2019
    Co-Authors: Zhengtao Zhao, Milena Corredig, Zafir Gaygadzhiev
    Abstract:

    Milk Protein Concentrates are common ingredients in the dairy industry, with varying processing histories and composition. The objective of this research was to determine the feasibility of using the whey Protein nitrogen (WPN) index, a well-established index for skim Milk powder and nonfat dry Milk, as a quality parameter for Milk Protein Concentrates. The WPN index is a value based on the moisture-adjusted weight of skim Milk powder. We hypothesized that WPN, even when standardized based on Protein, may change depending on solubilization conditions of Milk Protein Concentrates because of differences in solubilization conditions or processing history. The WPN was measured for model Concentrates with different thermal history or reconstitution conditions. The WPN was not affected by an increased concentration of soluble casein in the dispersions nor after solubilization of the powder at 22 or 60°C. All reconstituted samples were standardized for Protein. The WPN was also in full accordance with residual native Protein measured by chromatography.

  • effect of partial whey Protein depletion during membrane filtration on thermal stability of Milk Concentrates
    Journal of Dairy Science, 2018
    Co-Authors: Isis Rodrigues Toledo Renhe, Milena Corredig
    Abstract:

    Membrane filtration technologies are widespread unit operations in the dairy industry, often employed to obtain ingredients with tailored processing functionalities. The objective of this work was to better understand the effect of partial removal of whey Proteins by microfiltration (MF) on the heat stability of the fresh Concentrates. The micellar casein Concentrates were compared with control Concentrates obtained using ultrafiltration (UF). Pasteurized Milk was microfiltered (80 kDa polysulfone membrane) or ultrafiltered (30 kDa cellulose membrane) without diafiltration (i.e., no addition of water) to 2× and 4× concentration, based on volume reduction. The final Concentrates showed no differences in pH, casein micelle size, or mineral concentration in the serum phase. The micellar casein retentates (obtained by MF) showed a 20 and 40% decrease in whey Protein concentration compared with the corresponding UF Milk Protein Concentrates for 2× and 4× concentration, respectively. The heat coagulation time decreased with increasing Protein concentration, regardless of the treatment; however, MF retentates showed a higher thermal stability than the corresponding UF controls. The average diameter for casein micelles increased after heating in UF but not MF Concentrates. The turbidity (measured by light scattering) increased after heating, but to a higher extent for UF retentates than for MF retentates at the same Protein concentration. It was concluded that the reduced amount of whey Protein in the MF retentates caused a significant increase in the heat stability compared with the corresponding UF retentates. This difference was not due to ionic composition differences or pH, but to the type and amount of complexes formed in the serum phase.

  • Thermal stability of reconstituted Milk Protein Concentrates: Effect of partial calcium depletion during membrane filtration
    Food Research International, 2017
    Co-Authors: H. Eshpari, Rafael Jiménez-flores, Phil S. Tong, Milena Corredig
    Abstract:

    Abstract Milk Protein concentrate (MPC) powders are increasingly utilized in manufacturing of Protein fortified beverages. Thermal stability of the Protein dispersions is of significant importance in such applications. It is known that a decrease in pH can induce partial dissociation of casein micelles and modify the natural equilibrium of calcium and phosphate between the micelles and the serum phase. The presence of soluble casein may improve the rehydration properties of MPC powders, and may impact their thermal stability. The objective of this work was to investigate the effects of partial acidification of Milk prior to ultrafiltration on the heat stability of reconstituted MPC dispersions. Milk Protein concentrate powders were prepared from skim Milk acidified to pH 6.0 by addition of glucono-δ-lactone, and then concentrated using ultrafiltration (UF) and diafiltration (DF). The heat stability of the reconstituted MPC dispersions was studied, by determining heat coagulation time, particle size, turbidity, viscosity, soluble and colloidal calcium and phosphate, and non-sedimentable casein both before and after heating at 120 °C. Reconstituted MPC powders made with partially acidified skim Milk contained lower soluble calcium and phosphate and exhibited very poor thermal stability compared to MPC powders made with skim Milk at its natural pH. The thermal stability of the acidified MPC dispersions was not only recovered by restoration of pH and the serum composition through dialysis against skim Milk, but it was improved compared to control MPC dispersions. All dialyzed samples had comparable pH, Protein content and calcium and phosphate concentration, but the structure of the casein micelles was altered, causing differences in the type of soluble aggregates. It was concluded that the integrity of the casein micelles and the amount of dissociated, non-sedimentable caseins play a major role in determining the thermal stability of the MPC dispersions.

  • Changes in particle size, calcium and phosphate solubilization, and microstructure of rehydrated Milk Protein Concentrates, prepared from partially acidified Milk
    Dairy Science & Technology, 2016
    Co-Authors: H. Eshpari, Phil S. Tong, Milena Corredig
    Abstract:

    The present work studied the rehydration properties of Milk Protein Concentrates (MPCs), prepared using ultrafiltration (UF) and diafiltration (DF). Milk was acidified to pH 6 with glucono-δ-lactone (GDL) prior to UF to alter the mineral composition of the final Concentrates. The particle size distribution and the microstructure of the casein micelles in reconstituted MPCs as well as the partitioning of calcium, phosphate, and Proteins between the colloidal and soluble phases were investigated. Reconstituted samples analyzed by electron microscopy showed that, even in partially dissolved particles, the particle surface was porous and similar to its inner portion and had no distinct skin layer. Partial acidification of Milk did not have any significant effects on the microstructure; however, it significantly increased the average diameter of the casein micelles for both UF and DF samples and decreased the concentration of total calcium and phosphate. Sodium dodecyl sulfate (SDS)-PAGE analysis of the centrifugal supernatants of reconstituted MPC demonstrated that the amount of soluble caseins present in Milk Concentrates dramatically increased with acidification, and it further increased after restoring the mineral composition of the serum phase through dialysis against Milk. This work contributes to a better understanding of how processing conditions, particularly partial acidification of Milk prior to concentration, can alter the composition and physical properties of the caseins and the soluble phase of MPC after rehydration. Such alterations can significantly impact the technological properties of the reconstituted MPC.

Peng Zhou - One of the best experts on this subject based on the ideXlab platform.

  • effects of skim Milk pre acidification and retentate ph restoration on spray drying performance physico chemical and functional properties of Milk Protein Concentrates
    Food Chemistry, 2019
    Co-Authors: Dasong Liu, Jie Zhang, Xiaoming Liu, Joe M Regenstein, Yacine Hemar, Tianyi Yang, Peng Zhou
    Abstract:

    Abstract This study investigates the effects of pre-acidification (pH 6.7–5.4) of skim Milk, followed by pH-restoration of the retentates, on spray-drying performance, physico-chemical properties and functionality of the resulting Milk Protein concentrate (MPC). Powder recovery decreased with decreasing pH of pre-acidification but improved with pH-restoration. Colloidal calcium was gradually solubilized with decreasing pH of pre-acidification but was slightly recovered by pH-restoration. Dissociation of micellar caseins increased with decreasing pH of pre-acidification of skim Milk and was further increased by pH-restoration. Casein micelles maintained their overall structures at pre-acidification pH of 6.7–6.0, and partially disintegrated into loosely entangled aggregates at pH 5.7–5.4; while after pH-restoration, micelles generally maintained their overall structures at pre-acidification pH of 6.0, and completely disintegrated at pH 5.7–5.4. Solubility and emulsifying properties of MPC improved with decreasing pH of pre-acidification and with pH-restoration. Heat stability of MPC declined with decreasing pH of pre-acidification but improved with pH-restoration.

  • effect of partial acidification on the ultrafiltration and diafiltration of skim Milk physico chemical properties of the resulting Milk Protein Concentrates
    Journal of Food Engineering, 2017
    Co-Authors: Junke Li, Jie Zhang, Joe M Regenstein, Yacine Hemar, Miao Wang, Peng Zhou
    Abstract:

    Abstract This study investigates the effect of pre-acidification of skim Milk between pH 6.7–5.4 on the physico-chemical properties of the resulting Milk Protein concentrate as well as the membrane performance. The membrane filtration process comprised ultrafiltration and 3 stages of diafiltration each with a volume concentration factor of 3. With increasing number of processing stages at a given pH, both the colloidal calcium and micellar caseins were gradually dissociated, while the micellar hydration increased and the micellar size decreased. With the increase in processing stages, casein micelles generally maintained their intact structure between pH 6.7–6.0, and then partially disintegrated into loosely entangled Protein aggregates at pH 5.8–5.6, while complete micellar disruption occurred after extensive diafiltration at pH 5.4. Small-angle X-ray scattering indicated that the internal structure of the non-dissociated micelles became more homogenous when the number of processing stages increased and when the pre-acidification pH decreased.

  • effect of calcium sequestration by ion exchange treatment on the dissociation of casein micelles in model Milk Protein Concentrates
    Food Hydrocolloids, 2016
    Co-Authors: Dasong Liu, Hongxu Yang, Jie Zhang, Xiaoming Liu, Joe M Regenstein, Yacine Hemar, Peng Zhou
    Abstract:

    Abstract This study investigates the effect of partial depletion of Ca from Milk Protein Concentrates (MPCs) on the dissociation of the casein micelles. Series of MPCs with 0, 10.5, 19.6, 29.6, 38.7 and 83.6% decalcification were produced from the ultrafiltered-diafiltered retentate of skim Milk using ion exchange treatment. The amount of caseins dissociated from the casein micelles increased when decalcification was increased from 0 to 38.7%, while both the relative turbidity of the retentate and the z -average hydrodynamic diameter of casein micelle decreased markedly. Increasing decalcification to 83.6% caused no significantly additional changes in the amount of the dissociated caseins and the relative turbidity. As for casein micelles and colloidal calcium phosphate (CCP), transmission electron microscopy and small angle X-ray scattering (SAXS) showed that the micelle structure and CCP nanoclusters, respectively, were gradually dissociated at the beginning of the decalcification (0–38.7%), particularly at 38.7% where most of the casein micelles dissociated. SAXS indicated that most of the CCP nanoclusters were fully dissociated at 83.6% decalcification. This study offers a potential to manufacture MPCs with tailored functionalities, particularly for uses in dairy applications which require the dissociation of casein micelles.

Buddhi P Lamsal - One of the best experts on this subject based on the ideXlab platform.

  • Microstructural Changes in High-Protein Nutrition Bars Formulated with Extruded or Toasted Milk Protein Concentrate
    Journal of Food Science, 2016
    Co-Authors: J. C. Banach, S. Clark, Buddhi P Lamsal
    Abstract:

    Milk Protein Concentrates with more than 80% Protein (that is, MPC80) are underutilized as the primary Protein source in high-Protein nutrition bars as they impart crumbliness and cause hardening during storage. High-Protein nutrition bar texture changes are often associated with internal Protein aggregations and macronutrient phase separation. These changes were investigated in model high-Protein nutrition bars formulated with MPC80 and physically modified MPC80s. High-Protein nutrition bars formulated with extruded MPC80s hardened slower than those formulated with toasted or unmodified MPC80. Extruded MPC80 had reduced free sulfhydryl group exposure, whereas measurable increases were seen in the toasted MPC80. High-Protein nutrition bar textural performance may be related to the number of exposed free sulfhydryl groups in MPC80. Protein aggregations resulting from ingredient modification and high-Protein nutrition bar storage were studied with sodium dodecyl sulfate polyacrylamide gel electrophoresis. Disulfide-based Protein aggregations and changes in free sulfhydryl concentration were not consistently relatable to high-Protein nutrition bar texture change. However, the high-Protein nutrition bars formulated with extruded MPC80 were less prone to phase separations, as depicted by confocal laser scanning microscopy, and underwent less texture change during storage than those formulated with toasted or unmodified MPC80.

  • Texture and other changes during storage in model high-Protein nutrition bars formulated with modified Milk Protein Concentrates
    Lwt - Food Science and Technology, 2014
    Co-Authors: J. C. Banach, S. Clark, Buddhi P Lamsal
    Abstract:

    Abstract Extruded or toasted Milk Protein concentrate with approximately 80 g Protein per 100 g were incorporated into model high-Protein nutrition bars formulated at 30 g Protein per 100 g. The model high-Protein nutrition bars also contained other constituents, including glycerol, palm kernel stearin, sugar alcohol syrup, and high-fructose corn syrup, to mimic commercial high-Protein nutrition bars. The bars were stored at room temperature (∼22 °C), 32 °C, or 42 °C for up to 42 days. Texture, water activity, and color were measured periodically over the storage period. High-Protein nutrition bars formulated with unmodified Milk Protein concentrate served as the control and maintained similar texture to those high-Protein bars formulated with toasted Milk Protein concentrate. High-Protein nutrition bars prepared with Milk Protein concentrate extruded at 65 °C were significantly softer than the control. Significant differences in hardness and fracturability between high-Protein nutrition bars formulated with Milk Protein concentrate extruded at 120 °C and the control were intermittent over the storage period. Water activity of the high-Protein nutrition bars increased slightly during storage, but remained less than 0.65, which assured shelf stability. Surface color change was minimal at 22 °C storage, but increased at 32 °C and 42 °C.

  • Enzymatic modification of Milk Protein concentrate and characterization of resulting functional properties
    Lwt - Food Science and Technology, 2013
    Co-Authors: J. C. Banach, Zhuangsheng Lin, Buddhi P Lamsal
    Abstract:

    Abstract Milk Protein Concentrates are suitable ingredients for high-Protein beverages, but are underutilized due to poor solubility at ambient temperature and neutral pH. The other functional properties of Milk Protein concentrate, such as emulsification and foaming, depend on its solubility. Milk Protein concentrate with 80 g Protein 100 g −1 was hydrolyzed with three digestive enzymes – chymotrypsin, trypsin, and pepsin – and one cysteine protease – papain – to improve solubility and functionality. Two hydrolysates were produced with each enzyme at targeted levels of hydrolysis to help prevent the development of bitterness. Reduced urea sodium dodecyl sulfate polyacrylamide gel electrophoresis showed that casein subunits were more susceptible to hydrolysis compared with the whey Proteins. Enzyme hydrolysis improved the solubility of the Milk Protein concentrate in the pH range of 4.6–7.0 inclusive. All enzyme hydrolysates had reduced surface hydrophobicity and gel strength. Hydrolysis with chymotrypsin and trypsin improved emulsion activity and stability whereas emulsification capacity was improved with all enzymes. Foaming properties depended on enzyme and hydrolysis time. The hydrolysis of Milk Protein concentrate with food enzymes can improve solubility and alter resultant functional properties.

  • Characterization of Extruded and Toasted Milk Protein Concentrates
    Journal of Food Science, 2013
    Co-Authors: J. C. Banach, S. Clark, Buddhi P Lamsal
    Abstract:

    Important functional properties of Milk Protein concentrate with 80% Protein (MPC80), modified with low- and high-shear extrusion, or low-temperature toasting were compared. The effect of high- and low-shear profile screws in a corotating twin-screw extruder, and 4 different ramped temperature profiles with die temperatures of 65, 75, 90, and 120 °C were compared. Extrudates were pelletized, dried, and ground to a fine powder. Toasting was done at 75 and 110 °C for 4 h for Milk Protein modification. Extruded and toasted MPC80 had reduced Protein solubility and surface hydrophobicity. Extrusion decreased water-holding capacity (WHC). Toasted MPC80 had increased WHC when treated at 75 °C, but WHC decreased when heated at 110 °C. The treatments had no strong influence on gel strength. Reduced and nonreduced sodium dodecyl sulfate polyacrylamide gel electrophoresis revealed peptide structural changes that occurred due to processing, especially for whey Proteins. Results are discussed in terms of potential for application of extruded or toasted MPC80 in high-Protein nutrition bar applications. Practical Application Modified Milk Protein Concentrates may have the potential to substitute other Protein sources in high-Protein food applications.

H. Eshpari - One of the best experts on this subject based on the ideXlab platform.

  • Thermal stability of reconstituted Milk Protein Concentrates: Effect of partial calcium depletion during membrane filtration
    Food Research International, 2017
    Co-Authors: H. Eshpari, Rafael Jiménez-flores, Phil S. Tong, Milena Corredig
    Abstract:

    Abstract Milk Protein concentrate (MPC) powders are increasingly utilized in manufacturing of Protein fortified beverages. Thermal stability of the Protein dispersions is of significant importance in such applications. It is known that a decrease in pH can induce partial dissociation of casein micelles and modify the natural equilibrium of calcium and phosphate between the micelles and the serum phase. The presence of soluble casein may improve the rehydration properties of MPC powders, and may impact their thermal stability. The objective of this work was to investigate the effects of partial acidification of Milk prior to ultrafiltration on the heat stability of reconstituted MPC dispersions. Milk Protein concentrate powders were prepared from skim Milk acidified to pH 6.0 by addition of glucono-δ-lactone, and then concentrated using ultrafiltration (UF) and diafiltration (DF). The heat stability of the reconstituted MPC dispersions was studied, by determining heat coagulation time, particle size, turbidity, viscosity, soluble and colloidal calcium and phosphate, and non-sedimentable casein both before and after heating at 120 °C. Reconstituted MPC powders made with partially acidified skim Milk contained lower soluble calcium and phosphate and exhibited very poor thermal stability compared to MPC powders made with skim Milk at its natural pH. The thermal stability of the acidified MPC dispersions was not only recovered by restoration of pH and the serum composition through dialysis against skim Milk, but it was improved compared to control MPC dispersions. All dialyzed samples had comparable pH, Protein content and calcium and phosphate concentration, but the structure of the casein micelles was altered, causing differences in the type of soluble aggregates. It was concluded that the integrity of the casein micelles and the amount of dissociated, non-sedimentable caseins play a major role in determining the thermal stability of the MPC dispersions.

  • Changes in particle size, calcium and phosphate solubilization, and microstructure of rehydrated Milk Protein Concentrates, prepared from partially acidified Milk
    Dairy Science & Technology, 2016
    Co-Authors: H. Eshpari, Phil S. Tong, Milena Corredig
    Abstract:

    The present work studied the rehydration properties of Milk Protein Concentrates (MPCs), prepared using ultrafiltration (UF) and diafiltration (DF). Milk was acidified to pH 6 with glucono-δ-lactone (GDL) prior to UF to alter the mineral composition of the final Concentrates. The particle size distribution and the microstructure of the casein micelles in reconstituted MPCs as well as the partitioning of calcium, phosphate, and Proteins between the colloidal and soluble phases were investigated. Reconstituted samples analyzed by electron microscopy showed that, even in partially dissolved particles, the particle surface was porous and similar to its inner portion and had no distinct skin layer. Partial acidification of Milk did not have any significant effects on the microstructure; however, it significantly increased the average diameter of the casein micelles for both UF and DF samples and decreased the concentration of total calcium and phosphate. Sodium dodecyl sulfate (SDS)-PAGE analysis of the centrifugal supernatants of reconstituted MPC demonstrated that the amount of soluble caseins present in Milk Concentrates dramatically increased with acidification, and it further increased after restoring the mineral composition of the serum phase through dialysis against Milk. This work contributes to a better understanding of how processing conditions, particularly partial acidification of Milk prior to concentration, can alter the composition and physical properties of the caseins and the soluble phase of MPC after rehydration. Such alterations can significantly impact the technological properties of the reconstituted MPC.

  • Partial calcium depletion during membrane filtration affects gelation of reconstituted Milk Protein Concentrates
    Journal of Dairy Science, 2015
    Co-Authors: H. Eshpari, P S Tong, Rafael Jiménez-flores, Milena Corredig
    Abstract:

    Milk Protein concentrate powders (MPC) with improved rehydration properties are often manufactured using processing steps, such as acidification and high-pressure processing, and with addition of other ingredients, such as sodium chloride, during their production. These steps are known to increase the amount of serum caseins or modify the mineral equilibrium, hence improving solubility of the retentates. The processing functionality of the micelles may be affected. The aim of this study was to investigate the effects of partial acidification by adding glucono-δ-lactone (GDL) to skim Milk during membrane filtration on the structural changes of the casein micelles by observing their chymosin-induced coagulation behavior, as such coagulation is affected by both the supramolecular structure of the caseins and calcium equilibrium. Milk Protein Concentrates were prepared by preacidification with GDL to pH 6 using ultrafiltration (UF) and diafiltration (DF) followed by spray-drying. Reconstituted UF and DF samples (3.2% Protein) treated with GDL showed significantly increased amounts of soluble calcium and nonsedimentable caseins compared with their respective controls, as measured by ion chromatography and sodium dodecyl sulfate-PAGE electrophoresis, respectively. The primary phase of chymosin-induced gelation was not significantly different between treatments as measured by the amount of caseino-macropeptide released. The rheological properties of the reconstituted MPC powders were determined immediately after addition of chymosin, both before and after dialysis against skim Milk, to ensure similar serum composition for all samples. Reconstituted samples before dialysis showed no gelation (defined as tan δ=1), and after re-equilibration only control UF and DF samples showed gelation. The gelation properties of reconstituted MPC powders were negatively affected by the presence of soluble casein, and positively affected by the amount of both soluble and insoluble calcium present after reconstitution. This work, testing the chymosin-induced gelation behavior of various reconstituted MPC samples, clearly demonstrated that a decrease in pH to 6.0 during membrane filtration affects the integrity of the casein micelles supramolecular structure with important consequences to their processing functionality.

  • changes in the physical properties solubility and heat stability of Milk Protein Concentrates prepared from partially acidified Milk
    Journal of Dairy Science, 2014
    Co-Authors: H. Eshpari, P S Tong, Milena Corredig
    Abstract:

    A limiting factor in using Milk Protein Concentrates (MPC) as a high-quality Protein source for different food applications is their poor reconstitutability. Solubilization of colloidal calcium phosphate (CCP) from casein micelles during membrane filtration (e.g., through acidification) may affect the structural organization of these Protein particles and consequently the rehydration and functional properties of the resulting MPC powder. The main objective of this study was to investigate the effects of acidification of Milk by glucono-δ-lactone (GDL) before ultrafiltration (UF) on the composition, physical properties, solubility, and thermal stability (after reconstitution) of MPC powders. The MPC samples were manufactured in duplicate, either by UF (65% Protein, MPC65) or by UF followed by diafiltration (80% Protein, MPC80), using pasteurized skim Milk, at either the native Milk pH (~pH 6.6) or at pH 6.0 after addition of GDL, followed by spray drying. Samples of different treatments were reconstituted at 5% (wt/wt) Protein to compare their solubility and thermal stability. Powders were tested in duplicate for basic composition, calcium content, reconstitutability, particle size, particle density, and microstructure. Acidification of Milk did not have any significant effect on the proximate composition, particle size, particle density, or surface morphology of the MPC powders; however, the total calcium content of MPC80 decreased significantly with acidification (from 1.84 ± 0.03 to 1.59 ± 0.03 g/100 g of powder). Calcium-depleted MPC80 powders were also more soluble than the control powders. Diafiltered dispersions were significantly less heat stable (at 120°C) than UF samples when dissolved at 5% solids. The present work contributes to a better understanding of the differences in MPC commonly observed during processing.

Joe M Regenstein - One of the best experts on this subject based on the ideXlab platform.

  • effects of skim Milk pre acidification and retentate ph restoration on spray drying performance physico chemical and functional properties of Milk Protein Concentrates
    Food Chemistry, 2019
    Co-Authors: Dasong Liu, Jie Zhang, Xiaoming Liu, Joe M Regenstein, Yacine Hemar, Tianyi Yang, Peng Zhou
    Abstract:

    Abstract This study investigates the effects of pre-acidification (pH 6.7–5.4) of skim Milk, followed by pH-restoration of the retentates, on spray-drying performance, physico-chemical properties and functionality of the resulting Milk Protein concentrate (MPC). Powder recovery decreased with decreasing pH of pre-acidification but improved with pH-restoration. Colloidal calcium was gradually solubilized with decreasing pH of pre-acidification but was slightly recovered by pH-restoration. Dissociation of micellar caseins increased with decreasing pH of pre-acidification of skim Milk and was further increased by pH-restoration. Casein micelles maintained their overall structures at pre-acidification pH of 6.7–6.0, and partially disintegrated into loosely entangled aggregates at pH 5.7–5.4; while after pH-restoration, micelles generally maintained their overall structures at pre-acidification pH of 6.0, and completely disintegrated at pH 5.7–5.4. Solubility and emulsifying properties of MPC improved with decreasing pH of pre-acidification and with pH-restoration. Heat stability of MPC declined with decreasing pH of pre-acidification but improved with pH-restoration.

  • effect of partial acidification on the ultrafiltration and diafiltration of skim Milk physico chemical properties of the resulting Milk Protein Concentrates
    Journal of Food Engineering, 2017
    Co-Authors: Junke Li, Jie Zhang, Joe M Regenstein, Yacine Hemar, Miao Wang, Peng Zhou
    Abstract:

    Abstract This study investigates the effect of pre-acidification of skim Milk between pH 6.7–5.4 on the physico-chemical properties of the resulting Milk Protein concentrate as well as the membrane performance. The membrane filtration process comprised ultrafiltration and 3 stages of diafiltration each with a volume concentration factor of 3. With increasing number of processing stages at a given pH, both the colloidal calcium and micellar caseins were gradually dissociated, while the micellar hydration increased and the micellar size decreased. With the increase in processing stages, casein micelles generally maintained their intact structure between pH 6.7–6.0, and then partially disintegrated into loosely entangled Protein aggregates at pH 5.8–5.6, while complete micellar disruption occurred after extensive diafiltration at pH 5.4. Small-angle X-ray scattering indicated that the internal structure of the non-dissociated micelles became more homogenous when the number of processing stages increased and when the pre-acidification pH decreased.

  • effect of calcium sequestration by ion exchange treatment on the dissociation of casein micelles in model Milk Protein Concentrates
    Food Hydrocolloids, 2016
    Co-Authors: Dasong Liu, Hongxu Yang, Jie Zhang, Xiaoming Liu, Joe M Regenstein, Yacine Hemar, Peng Zhou
    Abstract:

    Abstract This study investigates the effect of partial depletion of Ca from Milk Protein Concentrates (MPCs) on the dissociation of the casein micelles. Series of MPCs with 0, 10.5, 19.6, 29.6, 38.7 and 83.6% decalcification were produced from the ultrafiltered-diafiltered retentate of skim Milk using ion exchange treatment. The amount of caseins dissociated from the casein micelles increased when decalcification was increased from 0 to 38.7%, while both the relative turbidity of the retentate and the z -average hydrodynamic diameter of casein micelle decreased markedly. Increasing decalcification to 83.6% caused no significantly additional changes in the amount of the dissociated caseins and the relative turbidity. As for casein micelles and colloidal calcium phosphate (CCP), transmission electron microscopy and small angle X-ray scattering (SAXS) showed that the micelle structure and CCP nanoclusters, respectively, were gradually dissociated at the beginning of the decalcification (0–38.7%), particularly at 38.7% where most of the casein micelles dissociated. SAXS indicated that most of the CCP nanoclusters were fully dissociated at 83.6% decalcification. This study offers a potential to manufacture MPCs with tailored functionalities, particularly for uses in dairy applications which require the dissociation of casein micelles.