Ultrafiltration Of Skim Milk Research Articles

Component Distribution, Shear-Flow Behavior, and Sol–Gel Transition in Mixed Dispersions of Casein Micelles and Serum Proteins

The shear flow and solid–liquid transition of mixed milk protein dispersions with varying concentrations of casein micelles (CMs) and serum proteins (SPs) are integral to key dairy processing operations, including microfiltration, ultrafiltration, diafiltration, and concentration–evaporation. However, the rheological behavior of these dispersions has not been sufficiently studied. In the present work, dispersions of CMs and SPs with total protein weight fractions (ωPR) of 0.021–0.28 and SP to total protein weight ratios (RSP) of 0.066–0.214 and 1 were prepared by dispersing the respective protein isolates in the permeate from skim milk ultrafiltration and then further concentrated via osmotic compression. The partition of SPs between the CMs and the dispersion medium was assessed by measuring the dry matter content and viscosity of the dispersion medium after separating it from the CMs via ultracentrifugation. The rheological properties were studied at 20 °C via shear rheometry, and the sol–gel transition was characterized via oscillatory measurements. No absorption of SPs by CMs was observed in dispersions with ωPR = 0.083–0.126, regardless of the RSP. For dispersions of SPs with ωPR ≤ 0.21, as well as the dispersion medium of mixed dispersions with ωPR = 0.083–0.126, the high shear- rate-limiting viscosity was described using Lee’s equation with an SP voluminosity (vSP) of 2.09 mL·g−1. For the mixed dispersions with a CM volume fraction of φCM ≤ 0.37, the relative high shear-rate-limiting viscosity was described using Lee’s equation with a CM voluminosity (vCM) of 4.15 mL·g−1 and a vSP of 2.09 mL·g−1, regardless of the RSP. For the mixed dispersions with φCM > 0.55, the relative viscosity increased significantly with an increasing RSP (this was explained by an increase in repulsion between CMs). However, the sol–gel transition was independent of the RSP and was observed at φCM ≈ 0.65.

Effect of Cavitation and High-Temperature Nanofiltration of Ultrafiltered Skim Milk on the Functionality of Milk Protein Concentrate Powder

Both hydrodynamic cavitation (HC) and temperature elevation are important pretreatments for improving the performance of liquid food processing by reducing viscosity. In this study, we assessed the impact of HC and elevated temperature on the functionality of milk protein concentrate powder with 80% protein (MPC80) prepared from nanofiltration (NF) of ultrafiltration (UF) retentate. Skim milk was concentrated using UF, and the retentate was further subjected to HC and concentrated using NF, then spray dried to obtain MPC80 powder. The functionality of these powders processed using NF at 22 °C, NF at 50 °C, HC and NF at 22 °C, and HC and NF at 50 °C were evaluated. Rennet coagulation time of reconstituted MPC80 from different NF treatments was like skim milk when treated with 0.1% CaCl2. High-temperature NF reduced the water solubility of MPC80 powder (70.03 to 79.20%) at room temperature, but it was similar when measured at 50 °C (86.05 to 92.91%). The HC improved foaming (92.22 to 112.89%) but did not impact the emulsifying capacity (59.58 to 61.38%) and heat stability (18.04 to 20.22 min). Results showed that the HC and high-temperature NF utilized to increase the production efficiency of MPC80 also maintained the functionality of the powders after spray drying.

Ultrafiltration: Impact of process temperature (7 and 50°C) on process performance and protein beverage physical, chemical, and sensory properties.

Our objectives were to determine the impact of ultrafiltration (UF) of skim milk at 7 and 50°C on UF processing, lactose removal, mineral partitioning, and skim milk retentate physical, chemical, and sensory properties at 3 (3.4 7.5, and 10.5%) protein concentration with 2 different heat processing treatments high temperature short time (HTST) pasteurization and autoclave). Pasteurized skim milk was split into 2 portions and the 7°C UF processing run was done on one day and the 50°C UF processing run was done on the next day. Skim milk was ultrafiltered and diafiltered at 7 and 50°C and as permeate was removed, deionized water at 7 or 50°C was added in an equal amount by weight as permeate removed to maintain constant protein concentration in the retentate during UF until 98% or more of lactose and low molecular weight soluble milk components were removed. All skim milk-based beverage bases from the 7 and 50°C UF of skim milk were HTST (78°C for 15 s) processed or autoclaved (116°C for 6 min). The physical, chemical, and sensory properties of all treatments were measured. This process was replicated twice with a new batch of pasteurized skim milk in a different week with the 7 and 50°C UF processing runs ran in reverse order. Overall, lactose-free skim milk at 3.4, 7.5, and 10.5% protein produced by UF with DF, was more bland, more white and less heat stable (i.e., stable to retorting but not direct steam injection at 142°C for 2 to 3 s) than skim milk based on both sensory scores and instrumental measures. A 98 to 99% removal of lactose from skim milk was achieved (final lactose concentration <0.06 g/100g) with a diafiltration ratio of water to milk of about 4 to 1 was used at both 7°C and 50°C. The processing time to achieve that lactose removal from the same starting weight of milk was about twice as long when filtering at 7°C than 50°C because of the lower flux (23 versus 48 kg/m2/h). The continuous DF at constant protein concentration maintained constant flux for a processing time of 4 and 8 h at 50 and 7°C, respectively. The final freezing point of the lactose and soluble mineral reduced milk was close to that of water (-0.015°C versus -0.525°C for skim milk) and the pH of the lactose-free milk at 20°C increased from about 6.5 for skim to about 7.33 and 7.46 for UF/DF skim milk at 7 and 50°C, respectively. Removal of compounds that absorb light (in the range of 360 to 500 nm) from milk in the permeate, increased light reflectance and whiteness and decreased yellowness relative to the starting skim milk.

Fat matters: Fermented whole milk potentiates the anti-colitis effect of Propionibacterium freudenreichii

Inflammatory bowel diseases (IBD) constitute a growing concern in western countries. They coincide with gut microbiota dysbiosis, including a loss of immunomodulatory bacteria. Accordingly, probiotic products containing selected immunomodulatory bacterial strains mitigate IBD. Selected strains of Propionibacterium freudenreichii display promising modulatory properties and prevent colitis in animal models. Dairy matrices protect propionibacteria immunomodulatory surface antigens during digestive transit. However, the functional role of the dairy matrix components in such fermented dairy products remains unknown. In the present workthis study, P. freudenreichii CIRM-BIA129, a probiotic strain known for its anti-inflammatory properties, was used to ferment whole milk, skim milk or skim milk ultrafiltrate. The preventive potential of fermented products was tested in DSS-induced mice colitis, in comparison with their unfermented counterparts. P. freudenreichii-fermented milk prevented colitis. Dairy fat in the fermented product potentiated the anti-colitis effects of the probiotic. This work opens new perspectives for developing immunomodulatory functional fermented foods.

Effects of hydrodynamic cavitation and temperature on nanofiltration performance for concentrating ultrafiltered skim milk

The performance of nanofiltration (NF) as influenced by hydrodynamic cavitation (HC) and filtration temperature during the concentration of milk protein concentrate (MPC) was investigated. Pasteurised skim milk was concentrated using ultrafiltration (UF) to prepare UF retentate (MPC80, 20% total solids, TS), which was then further concentrated using NF at 22°C and 50°C with or without HC treatments until permeate flux declined to 0.1 L/m2/h. Results showed that UF retentate can be concentrated to higher TS (up to 31.5%) at higher filtration temperature or by applying HC, with synergistic effect in combination of both treatments, during NF.

Measuring pH of skim milk and milk permeate at ultra-high temperatures at laboratory and pilot scale

Changes in the pH of skim milk and skim milk ultrafiltration permeate on heating from 25 to 140 °C were examined. Results showed that the decrease in pH with increase in temperature up to 140 °C was not linear. Hydrogen ion release due to changes in the milk mineral balance were responsible for the reduction in pH with increase in temperature. The presence of milk proteins offered little buffering against the drop in pH. The precipitation of calcium phosphate resulted in sediment in milk permeate heated above ∼70 °C, but this did not occur in skim milk, with the pH remaining lower in milk permeate after heat treatment when measured at 25 °C. This study has shown that in-line pH measurements of milk at ultra-high temperatures is feasible, and could prove useful at laboratory and pilot-scale for studying interactions within, and stability of, more complex formulations with added minerals.

Homogenization and sodium hydrogen phosphate induced effect on physical and rheological properties of ultrafilterd concentrated milk.

The online version contains supplementary material available at 10.1007/s13197-021-05097-2.

Influence of Processing Temperature on Membrane Performance and Characteristics of Process Streams Generated during Ultrafiltration of Skim Milk.

The effects of processing temperature on filtration performance and characteristics of retentates and permeates produced during ultrafiltration (UF) of skim milk at 5, 20, and 50 °C were investigated. The results indicate that despite higher flux at 50 °C, UF under these conditions resulted in greater fouling and rapid flux decline in comparison with 5 and 20 °C. The average casein micelle diameter was higher in retentate produced at 5 and 20 °C. The retentate analysed at 5 °C displayed higher viscosity and shear thinning behaviour as compared to retentate analysed at 20 and 50 °C. Greater permeation of calcium and phosphorus was observed at 5 and 20 °C in comparison with 50 °C, which was attributed to the inverse relationship between temperature and solubility of colloidal calcium phosphate. Permeation of α-lactalbumin was observed at all processing temperatures, with permeation of β-lactoglobulin also evident during UF at 50 °C. All UF retentates were shown to have plasmin activity, while lower activity was measured in retentate produced at 5 °C. The findings revealed that UF processing temperature influences the physicochemical, rheological, and biochemical properties of, and thereby govern the resulting quality and functionality of, retentate- and permeate-based dairy ingredients.

Consequences of membrane aging on real or misleading evaluation of membrane cleaning by flux measurements

Skim milk ultrafiltration is worldwide used in dairy. Its management at industrial scale is based on the permeate flux mastering, the first bottleneck, and consequently on the nature of the overall fouling which is not yet fully understood with respect to the membrane lifespan. The second bottleneck is the mastering and control of the cleaning efficiency aiming at the full removal of the initial irreversible fouling mainly made of proteins. In this study, we have deliberately chemically aged several spiral wound membrane elements by filtering NaOCl solution (400 ppm in total free chlorine at pH 8.0 and 50 °C) up to a cumulative chlorine dose of 2,800 ppm.d. The critical/threshold and limiting fluxes have been proven to increase with the membrane ageing together with a decrease in their related transmembrane pressure. This suggest that, at industrial scale, UF might be managed with respect to the chlorine dose received by the membrane during its service life. SEM and Raman spectroscopy have been used to localise the initial irreversible fouling whereas ATR-FTIR was the tool to quantify proteins on membrane. Membrane cleaning was achieved by a non-oxidative alkaline detergent removing the hereafter called “removable fouling” whereas a “residual fouling” remained on/in the membrane. However, the following NaOCl treatment (achieved for disinfection purpose at industrial scale) also acts both as cleaner (polishing the alkaline step by removing part of the residual fouling) and as degradation agent toward the membrane. Unambiguously NaOCl induced a significant decrease in the membrane intrinsic hydraulic resistance associated with an increase of the irreversible fouling, either initial or residual, build during the following skim milk UF. This paper shows how degradation and fouling can transiently compensate each other and lead to the impression of an initial water flux recovery. This phenomenon can lead to misinterpretation of the membrane cleanliness in the specific case of aged membranes. Indeed, for a received chlorine dose close to 400 ppm.d at pH = 8.0, an irreversible residual fouling can remain, strongly anchored in/on the membrane with a water flux recovery after cleaning only 15% less than that of the pristine membrane. This residual fouling favours the rapid build-up of more and more irreversible fouling during the next skim milk filtration steps. However, with respect to the accuracy on flux measurement, the amplitude of the problem will be underestimated, preventing from getting rid of the first and crucial accumulated layers and consequently leading to an irreversible accelerated degrading process. Relationships have been found between the received chlorine dose and the aged membrane resistance and the residual irreversible fouling that could be used for management at industrial scale.

Correlation between membrane surface properties, polymer nature and fouling in skim milk ultrafiltration

The fouling of the membranes in skim milk ultrafiltration with the nominal molecular weight cut-off (MWCO) of 100 kDa fabricated from different polymers (polysulfone (PSF), polysulfonamide (PSA), aromatic polyamide (PA), polyacrylonitrile (PAN), cellulose acetate (CA) and regenerated cellulose (RC)) was studied. The membrane structure and physical-chemical properties of the selective layer were analyzed using scanning electron microscopy (SEM), atomic force microscopy (AFM), water contact angle (θ, °) measurements, free surface energy measurements and bovine serum albumin (BSA) adsorption. Additionally, the flux of the skim milk at the constant product concentration, protein adsorption, resistance of the gel layer of the membranes were determined. It was found that according to the decrease in water contact angle of the membrane selective layers membranes can be arranged in the series as follows: PSF > PSA > PA > PAN > CA > RC. It was revealed that there was no direct correlation between the membrane hydrophilicity and the protein adsorption. It was noted, that the studied membranes featured significantly different hydraulic resistances of the protein gel-layer, which can be considered as a secondary dynamic membrane. Comparison of the parameters – water contact angle and polar component of the free surface energy of the membrane selective layer, and normalized dipole moment of the membrane polymers - with the adsorption values of the proteins during ultrafiltration proves that the protein adsorption to the membrane surface increases with an increase in hydrophobicity and polarity of the membrane. The high protein adsorption by the moderately hydrophilic PAN membrane is due to the contribution of the high normalized dipole moment of the polymer. In the case of the polar RC-100 membrane, the influence of the membrane polarity was shown to be counter-balanced by its high hydrophilicity. The study highlights the impact of the physical-chemical properties and structure of the membrane on the protein gel-layer and thus their importance in membrane fouling control in dairy applications.

Concentrated whey as protein source for thermally stabilized whey protein-pectin complexes

The suitability of ultrafiltered skim milk microfiltration permeate, concentrated ‘ideal whey’, (Wcon) as protein source in comparison to whey protein isolate (WPI) for thermomechanical whey protein-pectin complex (WPPC) formation with a scraped-surface heat exchanger on laboratory scale was investigated. Protein concentrations were between clow = 0.7% and chigh = 5.20% (protein:pectin = 5:1) and representative shear rates γ˙rep ranged from 150 to 675 s−1. WPPCs were analyzed by intrinsic fluorescence spectroscopy, static light scattering, light microscopy, and apparent particle binding energies σ* were calculated.With increasing γ˙rep WPPC size decreased. An influence of protein source on complex assembly was found as σ* was about four times higher whilst using Wcon instead of WPI (at equal c). Finally, Wcon (at γ˙rep≥ 500 s−1) is suitable to obtain WPPCs with desired properties (primary complexes with d90,3 < 10 μm) for applications as fat-replacers in dairy matrices.

Effect of change in pH, heat treatment and diafiltration on properties of medium protein buffalo milk protein concentrate.

The demand of milk protein concentrate (MPC) powders is continuously increasing as high protein dairy ingredients. Presence of higher calcium and casein contents; heating, ultrafiltration (UF), diafiltration (DF) and spray drying of buffalo skim milk induces undesirable changes in milk proteins that causes problem of poor solubility in MPC powders. Therefore, this investigation was aimed to study the effect of change in pH (6.8-native, 7.0-neutral), heat treatments (74 ± 1°C/15s, 80 ± 1°C/5min, 85 ± 1°C/5min, 90 ± 1°C/5min) and DF on physicochemical, functional, reconstitution and rheological properties of medium protein buffalo milk protein concentrate (MP-BMPC) powder. Based on maximum ζ-potential and heat stability, UF retentate was selected, diafiltered and spray dried to obtain MP-BMPC powder. Despite having higher protein content, MP-BMPC powder exhibited markedly better functional (solubility, wettability, viscosity and emulsion stability) properties than buffalo milk protein concentrate 60. The interstitial air content, occluded air content, loose bulk density, packed bulk density, particle density and porosity values of MP-BMPC powder were 145.97 and 112.92mL 100g-1 of powder, 0.21gmL-1, 0.30gmL-1, 0.55gmL-1 and 65.09%. Further, its specific surface area; particle size distribution (d10, d50, d90); Sauter (D32) and DeBroukere (D43) mean values were 97.93m2 kg-1; 34.32, 104.42, 218.58µm; 61.27µm and 117.99µm. The storage modulus (G') and loss modulus (G″) crossover temperature of UF and DF retentates were ~ 57.16°C and 55.10°C, respectively. Rheological behaviour of UF, DF retentates and MP-BMPC solution were best explained by Herschel-Bulkley model. Fourier-transform infrared spectroscopy best described amide I, II and III regions in 1700-1400cm-1 and 1350-1200cm-1 wavenumber range.

Simulation of membrane ageing to go ahead in fouling and cleaning understanding during skim milk ultrafiltration

In dairy industry, the mastering of membrane fouling and cleaning remains a bottleneck of membrane processes especially for aged and degraded membranes. This paper reports an in-depth study of the impact of membrane chemical ageing due to NaOCl disinfection on the fouling and cleaning of PES/PVP membranes.Fouling by skim milk was performed at critical and limiting flux found to have an impact on the initial irreversible fouling, i.e. the one remaining after water rinsing. Furthermore, for filtrations performed with pristine membranes, the fouling removal by formulated alkaline detergents was also affected by the filtration conditions.On the contrary, aged membranes were highly irreversibly fouled whatever the operating conditions. Furthermore, they were shown to be more difficult to clean than pristine ones.Besides these results, this study provides the validation of an original approach based on the use of micro-waves activation to study the membrane degradation.

Membrane-based fractionation, enzymatic dephosphorylation, and gastrointestinal digestibility of β-casein enriched serum protein ingredients

This study aims to produce a serum protein ingredient enriched with dephosphorylated β-casein from skim milk for infant formula manufacture using ceramic membrane filtration combined with enzymatic dephosphorylation. Compared to filtration at 25 °C or using skim milk ultrafiltration permeates as a diafiltrant, filtration at 4 °C using water as a diafiltrant improved the selective co-enrichment of β-casein with whey proteins in the permeates, resulting in a serum protein ingredient with 49% β-casein, 45% whey proteins and 6% of other caseins after microfiltration and 4-stage diafiltration. Subsequent incubation with phosphatase achieved 0–97% casein dephosphorylation, and β-casein showed multi-dephosphorylated isoforms depending on dephosphorylation extent. With increased dephosphorylation, β-casein enriched serum protein ingredients formed looser gastric clots with greater gastrointestinal digestibility under infant in vitro model conditions. These results offer a potential to develop a multi-functional serum protein ingredient with a casein profile (composition/phosphorylation) close to human milk for use in infant formula.

Influence of diafiltration on flux decline during skim milk ultrafiltration

The effect of lactose and mineral removal during diafiltration on physicochemical properties of skim milk and flux decline behaviour during ultrafiltration was investigated. Diafiltration mainly resulted in a significant decrease in ionic strength, primarily due to mineral removal. This corresponded to a significant increase in flux, solely due to a decrease in the concentration polarisation resistance (RCP), which can be attributed to stronger repulsive electrostatic interactions between the retained casein micelles (and whey proteins) in the polarised concentration layer at the membrane surface, resulting in a less densely packed and more permeable particle layer. RCP exhibited a strong correlation with ionic strength in the range of ionic strengths investigated (32–85 mm). The strong dependence of RCP on ionic strength was considered to remain valid at lower ionic strengths, given the minor impact of more extensive diafiltration on the physical properties of casein micelles previously reported in literature.

Effects of milk heat treatment and solvent composition on physicochemical and selected functional characteristics of milk protein concentrate

Milk protein concentrate (MPC) powders (∼81% protein) were made from skim milk that was heat treated at 72°C for 15 s (LHMPC) or 85°C for 30 s (MHMPC). The MPC powder was manufactured by ultrafiltration and diafiltration of skim milk at 50°C followed by spray drying. The MPC dispersions (4.02% true protein) were prepared by reconstituting the LHMPC and MHMPC powders in distilled water (LHMPCw and MHMPCw, respectively) or milk permeate (LHMPCp and MHMPCp, respectively). Increasing milk heat treatment increased the level of whey protein denaturation (from ∼5 to 47% of total whey protein) and reduced the concentrations of serum protein, serum calcium, and ionic calcium. These changes were paralleled by impaired rennet-induced coagulability of the MHMPCw and MHMPCp dispersions and a reduction in the pH of maximum heat stability of MHMPCp from pH 6.9 to 6.8. For both the LHMPC and MHMPC dispersions, the use of permeate instead of water enhanced ethanol stability at pH 6.6 to 7.0, impaired rennet gelation, and changed the heat coagulation time and pH profile from type A to type B. Increasing the severity of milk heat treatment during MPC manufacture and the use of permeate instead of water led to significant reductions in the viscosity of stirred yogurt prepared by starter-induced acidification of the MPC dispersions. The current study clearly highlights how the functionality of protein dispersions prepared by reconstitution of high-protein MPC powders may be modulated by the heat treatment of the skim milk during manufacture of the MPC and the composition of the solvent used for reconstitution.

Influence of processing temperature on flux decline during skim milk ultrafiltration

The flux decline behaviour during skim milk ultrafiltration (UF) was investigated at 10 °C, 30 °C and 50 °C. Despite higher fluxes, UF processing at higher temperatures resulted in higher magnitudes and rates of irreversible fouling. Fouling in this temperature range was primarily proteinaceous, consisting of mainly peptides and alpha-lactalbumin (α-LA), with minor amounts of beta-lactoglobulin (β-LG) present only at 50 °C. The increase in fouling resistance with processing temperature was concluded to be mainly due to increased pore fouling by α-LA deposition, and in part to β-LG deposition at 50 °C. These are attributed respectively to the thermal expansion of membrane pores and reversible conformational changes of β-LG.

Effect of chelators on functionality of milk protein concentrates obtained by ultrafiltration at a constant pH and temperature.

Modulating conditions during ultrafiltration of skim milk appears to be a feasible strategy to obtain milk protein concentrates (MPC) with tailored functionalities. Adjustment of pH and process temperature attenuated properties of casein micelle resulting in enhanced emulsification capacity. Additional pre-treatment options such as addition of calcium chelators can further impact on the functionality of MPC by modifying the calcium distribution and casein micelle integrity. The objective of the project was to establish effects of pre-treating skim milk with calcium chelators (EDTA or citrate) in concentrations between 10 to 30 mm prior to UF on the physical properties of the feed, corresponding retentates and dried MPC, including particle size, zeta potential and calcium distribution in skim milk and the corresponding retentates, as well as the physical functionalities such as solubility, heat stability and emulsifying properties. Addition of calcium chelators (EDTA or citrate), at levels 20-30 mm concentrations reduced casein micelle size as well as total, soluble and ionic calcium contents that resulted in MPC with enhanced solubility and heat stability. The emulsion capacity was, however, improved only with EDTA at 10 mm concentration. The enhanced functionality is attributed to the reduced particle size resulting from the removal of calcium from the retentate that could modify micellar casein to an extent sufficient to cause such improvements.

Effect of partial acidification on the ultrafiltration and diafiltration of skim milk: Physico-chemical properties of the resulting milk protein concentrates

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.

The effect of emulsifying salts on the turbidity of a diluted milk system with varying pH and protein concentration

Solutions of 10 commonly used emulsifying salts (ES) listed in the Code of Federal Regulations (21CFR133.179) for pasteurized process cheese were tested for their effect on the turbidity of a diluted milk system at different pH and protein concentrations to characterize the conditions that affect micellar structure. Emulsifying salt solutions were made by mixing the ES in a 1-in-20 dilution of water in skim milk ultrafiltrate (3 kDa molecular weight cut-off) to obtain ES concentrations from 0 to 248 mM. Skim milk was added to solutions containing nanopure water, skim milk ultrafiltrate, and a specific ES ranging in concentration from 0 to 248 mM and pH 5, 5.8, 6.8, 7.8, and 8.8. The turbidity of the samples was measured as the optical density at 400 nm immediately after mixing (time, t = 0), after 30 s (t = 30s), and after 30 min (t = 30min). Emulsifying salts were found to cause a decrease in the turbidity of the system, which was modeled using an exponential decay model, where C* represents a threshold salt concentration at which rapid dissociation occurs. At pH values 5.8 and 6.8, the ES caused the greatest decrease in turbidity of the diluted milk system. At pH 5, the ES had the least effect on the turbidity of the system. Sodium hexametaphosphate was found to have the strongest dissociative effect, with a C* value of 0.33 mM for t = 0 at pH 6.8. In contrast, the largest C* value calculated at pH 6.8 was monosodium phosphate at 278.22 mM. Increased time resulted in lower C* values. The model established for this study can be used to predict the dissociation of casein micelles in the presence of various types of ES.