A Review on the Effect of Calcium Sequestering Salts on Casein Micelles: From Model Milk Protein Systems to Processed Cheese

Enhancing casein micelle dissociation in diluted skim milk systems using combined processing techniques

The present work aims to evaluate the dissociation of casein micelles in diluted skim milk (SM) systems after undergoing solvent- or emulsifying salt-based dissociation coupled with ultra-high-pressure homogenization (UHPH). Specifically, part I evaluated dilute SM solutions combined with varying ethanol concentrations (0%-60%) at varying temperatures (5-65°C) in combination with UHPH (100-300 MPa), and part II evaluated dilute SM solutions combined with varying concentrations (0-100 mM) of either sodium hexametaphosphate (SHMP) or sodium citrate (SC) in combination with UHPH (100-300 MPa). In part I, high concentrations of ethanol (40%-60% vol/vol) at elevated temperatures (45-65°C) achieved extensive dissociation of casein micelles, especially in combination with UHPH at ≥200 MPa, as shown by a reduction in sample absorbance and in casein particle size compared with the control (dilute SM, 65°C) under optimum conditions (dilute SM, 60% ethanol, 65°C, ≥200 MPa). In part II, the level of casein micelle dissociation using emulsifying salts (ES) was dependent on the ES type and concentration. Considerable casein micelle dissociation in dilute SM systems was achieved with SHMP concentrations ≥1 mM and SC concentrations ≥10 mM, resulting in decreased sample absorbance, bimodal casein size distributions, and increased hydrophobicity (∼2-fold increase in intrinsic fluorescence) compared with the control (dilute SM). This dissociation was further enhanced with UHPH (≥200 MPa). These results indicate that both solvent- and ES-based casein dissociation techniques can be optimized when used in combination with UHPH. Together, these processing techniques can be used to extensively dissociate casein micelles with the potential to use these altered systems for value-added applications such as functional ingredients or encapsulation agents.

The contrasting roles of co-solvents in protein formulations and food products

Protein aggregation is a major hurdle in developing biopharmaceuticals, in particular protein formulation area, but plays a pivotal role in food products. Co-solvents are used to suppress protein aggregation in pharmaceutical proteins. On the contrary, aggregation is encouraged in the process of food product making. Thus, it is expected that co-solvents play a contrasting role in biopharmaceutical formulation and food products. Here, we show several examples that utilize co-solvents, e.g., salting-out salts, sugars, polyols and divalent cations in promoting protein-protein interactions. The mechanisms of co-solvent effects on protein aggregation and solubility have been studied on aqueous protein solution and applied to develop pharmaceutical formulation based on the acquired scientific knowledge. On the contrary, co-solvents have been used in food industries based on empirical basis. Here, we will review the mechanisms of co-solvent effects on protein-protein interactions that can be applied to both pharmaceutical and food industries and hope to convey knowledge acquired through research on co-solvent interactions in aqueous protein solution and formulation to those involved in food science and provide those involved in protein solution research with the observations on aggregation behavior of food proteins.

Influence of calcium sequestering salt type and concentration on the characteristics of processed cheese made from Gouda cheese of different ages

The effect of 90, 180 and 270 mEq/kg of the calcium sequestering salts (CSS) disodium phosphate (DSP), trisodium citrate (TSC) and sodium hexametaphosphate (SHMP) on the solubilisation of proteins and minerals and the rheological and textural properties of processed cheese (PC) prepared from Gouda cheese ripened for 30-150 d at 8°C was studied. The solubilisation of individual caseins and Ca and the maximum loss tangent during temperature sweeps of PC made from Gouda cheese increased, while hardness of PC decreased with ripening duration of the Gouda cheese. Levels of soluble Ca in PC increased with increasing concentration of TSC and SHMP, but decreased with increasing concentration of DSP. The solubilisation of casein and Ca due to ripening of Gouda cheese used for manufacturing PC could explain the changes in texture and loss tangent of PC. The results suggest that DSP, TSC or SHMP in PC formulation can form insoluble Ca-phosphate, soluble Ca-citrate or insoluble casein-Ca-HMP complexes, respectively, that influence casein solubilisation differently and together with levels of residual intact casein determine the functional attributes of PC.

Soluble Salts in Processed Cheese Prepared with Citrate- and Phosphate-Based Calcium Sequestering Salts

In this study, the protein and salts distribution (Ca, P, Na and Mg) in processed cheese (PC) samples prepared with 180 or 360 mEq/kg of the calcium sequestering salts (CSS) disodium phosphate (DSP), disodium pyrophosphate (DSPP), sodium hexametaphosphate (SHMP) and trisodium citrate (TSC) was studied. For this purpose, a water-soluble extract (WSE) of PC samples was prepared. All PC samples contained 45-46% moisture, 26-27% fat and 20-21% protein and had a pH of 5.2 or 5.7. Ultracentrifugation slightly reduced the protein content of the WSE of PC, indicating that most protein in the WSE was non-sedimentable. At equal concentration of CSS, the protein content of the WSE was higher for PC at pH 5.7 compared to PC at pH 5.2. Approximately 55-85% of the Ca and P in the WSE of samples was 10 kDa-permeable for PC prepared with DSPP and SHMP. This suggests that the formation of non-permeable Ca-polyphosphate-casein complexes. For PC prepared with TSC, >90% of Ca in the WSE was 10 kDa-permeable, indicating that micellar disruption arises from sequestration of micellar Ca. These results indicate that the WSE method is an appropriate method to understand how salts present in PC are distributed. However, the WSE and ultracentrifugal supernatant of the WSE can include both soluble and protein-associated salts. Therefore, determining levels of salts in 10 kDa permeate of ultracentrifugal supernatant of the WSE is most appropriate.

A Review on the Production and Characteristics of Cheese Powders

Cheese powder is a product resulting from the removal of moisture from cheese. At first, cheese emulsion is prepared by dissolving cheese(s) with water and calcium sequestering salts followed by drying. The desirable characteristics of cheese powder are high solubility, no lumps, storage stability, and imparting a typical cheesy flavor to the final product. Many current studies on cheese powder are focused on reducing calcium-sequestering salts (CSSs) to reduce the sodium content of cheese powder. This review discusses the production processes and physio-chemical properties of cheese emulsions and powders, aiming to enhance current understanding and identifying potential research gaps. Furthermore, strategies for producing cheese powder without CSSs, including pH adjustment, homogenization, and addition of dairy components such as buttermilk powder and sodium caseinate, are elaborated upon. Processing variables such as heating conditions during the preparation of cheese emulsion may vary with the type and age of the cheese used and product formulation. These conditions also effect the characteristics of cheese powders. On the other hand, producing a stable cheese emulsion without CSSs is challenging due to impaired emulsification of fat. The combined use of buttermilk powder and sodium caseinate among various alternatives has shown promising results in producing cheese powder without CSSs. However, future research on replacing CSSs should focus on combining two or more strategies together to produce cheese powder without CSSs. The combination of pH adjustment and dairy ingredients and the use of novel processing technologies with different ingredients are interesting alternatives.

Influence of acidification and re-neutralization on mineral equilibria and physicochemical properties of model cheese feed

Cheese feed is used as spray-dryer feed in cheese powder production, where there is growing consumer demand to eliminate calcium-chelating salts (ES). To develop ES-free feed production processes, it is essential to investigate the relationship between pH, structural changes, and mineral solubilization. This study investigated the influence of acidification and pH re-neutralization on calcium equilibria and stability of ES-free model cheese feeds. The goal was to increase protein availability by solubilizing colloidal calcium phosphate (CCP) and to assess whether CCP solubilization is reversible upon re-neutralization. The extent of acidification (to pH 4.2 or pH 4.7) significantly affected the irreversibility of calcium solubilization upon re-neutralization. Moreover, re-neutralization treatment seemed to induce changes in protein-fat interactions. Feed viscosity was mainly influenced by the final pH, rather than the re-neutralization history. These results offer new insights into the complex interplay of pH, structural modifications, mineral solubilization, and stability in cheese feed production.

Bovine milk β-casein: Structure, properties, isolation, and targeted application of isolated products

β-Casein, an important protein found in bovine milk, has significant potential for application in the food, pharmaceutical, and other related industries. This review first introduces the composition, structure, and functional properties of β-casein. It then reviews the techniques for isolating β-casein. Chemical and enzymatic isolation methods result in inactivity of β-casein and other components in the milk, and it is difficult to control the production conditions, limiting the utilization range of products. Physical technology not only achieves high product purity and activity but also effectively preserves the biological activity of the components. The isolated β-casein needs to be utilized effectively and efficiently for various purity products in order to achieve optimal targeted application. Bovine β-casein, which has a purity higher than or close to that of breast β-casein, can be used in infant formulas. This is achieved by modifying its structure through dephosphorylation, resulting in a formula that closely mimics the composition of breast milk. Bovine β-casein, which is lower in purity than breast β-casein, can be maximized for the preparation of functional peptides and for use as natural carriers. The remaining byproducts can be utilized as food ingredients, emulsifiers, and carriers for encapsulating and delivering active substances. Thus, realizing the intensive processing and utilization of bovine β-casein isolation. This review can promote the industrial production process of β-casein, which is beneficial for the sustainable development of β-casein as a food and material. It also provides valuable insights for the development of other active substances in milk.

Effect of Moderate Electric Fields on the Physical and Chemical Characteristics of Cheese Emulsions

Cheese powder is a multifunctional ingredient that is produced by spray drying a hot cheese emulsion called cheese feed. Feed stability is achieved by manipulating calcium equilibrium using emulsifying salts. However, the increased demand for 'green' products created a need for alternative production methods. Therefore, this study investigated the impact of ohmic heating (OH) on Cheddar cheese, mineral balance, and the resulting cheese feed characteristics compared with a conventional method. A full factorial design was implemented to determine the optimal OH parameters for calcium solubilization. Electric field exposure and temperature had a positive correlation with mineral solubilization, where temperature had the greatest impact. Structural differences in pre-treated cheeses (TC) were analyzed using thermorheological and microscopic techniques. Obtained feeds were analyzed for particle size, stability, and viscosity. OH-treatment caused a weaker cheese structure, indicating the potential removal of calcium phosphate complexes. Lower component retention of OH_TC was attributed to the electroporation effect of OH treatment. Microscopic images revealed structural changes, with OH_TC displaying a more porous structure. Depending on the pre-treatment method, component recovery, viscosity, particle size distribution, and colloidal stability of the obtained feeds showed differences. Our findings show the potential of OH in mineral solubilization; however, further improvements are needed for industrial application.

Influence of Calcium-Sequestering Salts on Heat-Induced Changes in Blends of Skimmed Buffalo and Bovine Milk

Heat-induced interactions of calcium and protein in milk lead to undesirable changes in the milk, such as protein coagulation, which can be minimized through the addition of calcium-sequestering salts prior to heat treatment. Thus, the present study investigated the influence of 5 mM added trisodium citrate (TSC) or disodium hydrogen phosphate (DSHP) on the heat-induced (85 °C and 95 °C for 5 min) changes in physical, chemical, and structural properties of buffalo and bovine skim milk mixtures (0:100, 25:75, 50:50, 75:25, and 100:0). Significant changes in pH and calcium activity as a result of TSC or DSHP addition subsequently resulted in higher particle size and viscosity as well as non-sedimentable protein level. These changes are mostly observed during heat treatment at 95 °C and increased proportionally to the concentration of buffalo skim milk in the milk mixture. Significant changes were affected by TSC addition in the 75:25 buffalo:bovine milk blend and buffalo skim milk, but for other milk samples, TSC addition effected comparable changes with DSHP addition. Overall, the addition of TSC or DSHP before heat treatment of buffalo:bovine milk blends caused changes in milk properties that could reduce susceptibility of milk to coagulation.