Caseinate , emulsification properties

Emulsification properties. Caseins and caseinates are commonly selected for food product applications that require surfactant properties, e.g., emulsification and foam stabilization, since they contain high protein contents of > 90 %, are highly soluble, and are resistant to heat-induced denaturatlon in products to be subjected to high temperature processing conditions (15). 

Emulsification properties in model food systems. Pearson et al. (25) investigated the emulsification properties of caseinate and NFDM in model emulsion systems produced by blending soybean oil into an aqueous buffer system as a function of pH and ionic strength (Figures 7 and 8). They found that caseinate exhibited good emulsification properties under all pH and ionic strength conditions studied, but was particularly effective at pH 10.4. 

The emulsification properties of NFDM were slightly better than for caseinate at all protein levels. However. NFDM exhibited lowest emulsification properties at pH 10.4 and highest emulsification at pH 5.6, which was directly opposite the results with caseinate. Thus, the molecular state of caseins, whether in the. micellar or soluble complex form is important in determining their functionality as an emulsifier. 

Whey protein concentrates (WPC), which are relatively new forms of milk protein products available for emulsification uses, have also been studied (4,28,29). WPC products prepared by gel filtration, ultrafiltration, metaphosphate precipitation and carboxymethyl cellulose precipitation all exhibited inferior emulsification properties compared to caseinate, both in model systems and in a simulated whipped topping formulation (2. However, additional work is proceeding on this topic and it is expected that WPC will be found to be capable of providing reasonable functionality in the emulsification area, especially if proper processing conditions are followed to minimize protein denaturation during their production. Such adverse effects on the functionality of WPC are undoubtedly due to their Irreversible interaction during heating processes which impair their ability to dissociate and unfold at the emulsion interface in order to function as an emulsifier (22). 

Figure 9. Emulsification properties of sodium caseinate in the absence of chemical emulsifiers (26)...

It is essential to consider the physico-chemical properties of each WPC and casein product in order to effectively evaluate their emulsification properties. Otherwise, results merely indicate the previous processing conditions rather than the inherent functional properties for these various products. Those processing treatments that promote protein denaturatlon, protein-protein Interaction via disulfide interchange, enzymatic modification and other basic alterations in the physico-chemical properties of the proteins will often result in protein products with unsatisfactory emulsification properties, since they would lack the ability to unfold at the emulsion interface and thus would be unable to function. It is recommended that those factors normally considered for production of protein products to be used in foam formation and foam stabilization be considered also, since both phenomena possess similar physico-chemical and functionality requirements (30,31). 

J. Al-Hakkak and S. Kavale, Improvement of emulsification properties of sodium caseinate by conjugating to pectin through the Maillard reaction, in G, 2002, 491—499. 

Hogan, S.A., McNamee, B. F., O Riordan, E. D., O Sullivan, M. (2001). Emulsification and microencapsulation properties of sodium caseinate/carbohydrate blends. International Dairy Journal, 11, 137-144. 

The casein retentate, when used as cheese milk, can almost be fully depleted of all whey proteins through a sufficient number of diafiltration volume turnovers. In contrast to conventional cheese technology, it is then possible to UHT treat the cheese milk in order to destruct spore formers. The whey proteins can be used as a WPG or WPI product or treated further in order to fractionate the whey proteins in their main components. Alternatively the whey proteins can particulated to form WPP see Section 19.5.1. Both approaches are options to build a platform for novel product matrices with specific properties such as gelling, foaming or emulsification. 

As with other viscous polyanions such as carrageenan, pectin may be protective towards milk casein colloids, enhancing the properties (foam stability, solubility, gelation and emulsification) of whey proteins whilst utilizing them as a source of calcium. 

Acylation affects the casein micelles of milk. The main effects are increased dissolution of the calcium and phosphate from the micelle and increased solubilization of caseins as a consequence of acylation (Vidal et al., 2002). As the equilibria of caseins between the micellar and serum phases are known to affect a number of functional properties (e.g., gelation, emulsification), it may be expected that acylation will affect functionality. 

The dissociation of a quaternary structure or denaturation of proteins is required prior to emulsification. Therefore, casein micelles are adsorbed at an interface in a semi-intact form (Oortwijn et al., 1977). The thermal denaturation of globular proteins prior to emulsification was reported to improve the emulsifying properties. The high level of the thermally denatured whey protein fraction in mixed proteins (of denatured and undenatured proteins) increased the emulsion viscosity and coalescence stability compared with the low-level denatured fraction (Britten et al., 1994). 

The valuable component of cheese whey is not the lactose but the whey proteins, primarily lactalbumin. The amino acid profile of these proteins is superior nutritionally to casein and is equal to or better than whole egg protein. The heat-denatured form of these proteins has been manufactured for many years usually by heating the cheese whey to precipitate the proteins. The product was tan colored and completely insoluble. With the advent of UF, these proteins could be recovered, concentrated and demineralized athermally. The result was a "whey protein concentrate" (WPC) with improved solubility and other functional properties (emulsification, foamability, water binding, gelation and cloud stability). 

About 50 years ago, the major uses of casein were in technogical appUcations, but nowadays casein products are regularly used as food additives, for example as ingredients that enhance some physical properties of foods, such as whipping, foaming, water binding, thickening and emulsification and nutritional properties. 

Uses Emulsifer, stabilizer, protein source in foods Features Prepared from fresh skimmed milk Properties Spray-dried neutral and bland taste and odor Sodium Caseinate Spray F P [Am. Casein]... 

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