Whey protein emulsion stabilization

Sun, C., Gunasekaran, S., Richards, M.P. (2007). Effect of xanthan gum on physicochemical properties of whey protein isolate stabilized oil-in-water emulsions. Food Hydrocolloids, 21, 555-564. 

Kiokias, S., Dimakou, C., and Oreopoulou, V. (2007). Effect of heat treatment and droplet size on the oxidative stability of whey protein emulsions. Food Chem. 105, 94-100. 

Table 10.5. Effect of different chelators on oxidative stability of algae oil-whey protein isolate-stabilized emulsions containing ca-3 polyunsaturated fatty acids"...

Hu M, McClements DJ, Decker EA (2004) Impact of chelators on the oxidative stability of whey protein isolate-stabilized oil-in-water emulsions containing x-3 fatty acids. Food Chem 88 57-62... 

Ice cream serves as a wonderful (and tasty) example of a complex, dynamically heterogeneous food system. A typical ice cream mix contains milk or cream (water, lactose, casein and whey proteins, lipids, vitamins, and minerals), sucrose, stabilizers and emulsifiers, and some type of flavor (e.g., vanilla). After the ingredients are combined, the mix is pasteurized and homogenized. Homogenization creates an oil-in-water emulsion, consisting of millions of tiny droplets of milk fat dispersed in the water phase, each surrounded by a layer of proteins and emulsifiers. The sucrose is dissolved in... 

Figure 3.2 Evolution of the microstructure of phase-separated biopolymer emulsion system containing pectin and 0.5 vt% heat-denatured (HD) whey protein isolate (WPI) stabilized oil droplets, (a) Composition 1U 3L (one-to-three mass ratio of upper and lower phases). The large circles are the water droplets (W), while the small circles are the oil droplets (O). This system forms a W2/W1-O/W1 emulsion, where O is oil, Wi is HD-WPI-rich and W2 is pectin-rich, (b) Composition 2U 2L. This system forms an 0/Wi/W2 emulsion, where O is oil, Wi is HD-WPI-rich and W2 is pectin-rich, (c) Composition 3U 1L. This system forms an 0/W]/W2 emulsion, where O is oil, Wi is HD-WPI-rich and W2 is pectin-rich. Reproduced from Kim et al. (2006) with permission.

Ye, A., Singh, H. (2000b). Influence of calcium chloride addition on the properties of emulsions stabilized by whey protein concentrate. Food Hydrocolloids, 14, 337-346. 

In a recent study by Sun et al. (2007) of 20 vol% oil-in-water emulsions stabilized by 2 wt% whey protein isolate (WPI), the influence of addition of incompatible xanthan gum (XG) was investigated at different concentrations. It was demonstrated that polysaccharide addition had no significant effect on the average droplet size (d32). But emulsion microstructure and creaming behaviour indicated that the degree of flocculation was a sensitive function of XG concentration with no XG present, there was no flocculation, for 0.02-0.15 wt% XG, there was a limited... 

In the study of Neirynck et al. (2007), the electrophoretic mobility data indicated that whey protein-stabilized emulsion droplets became gradually more negatively charged with pectin addition at pH = 5.5. This change was not only reflected in a smaller average droplet size, but also in a significant improvement in the creaming stability of the emulsions. 

Damianou, K., Kiosseoglou, V. (2006). Stability of emulsions containing a whey protein concentrate obtained from milk serum through carboxymethylcellulose complexation. Food Hydrocolloids, 20, 793-799. 

Gancz, K., Alexander, M., Corredig, M. (2006). In situ study of flocculation of whey protein-stabilized emulsions caused by addition of high-methoxy 1 pectin. Food Hydro-colloids, 20, 293-298. 

Khalloufi, S., Corredig, M., Goff, H.D., Alexander, M. (2009). Flaxseed gums and their adsorption on whey protein-stabilized oil-in-water emulsions. Food Hydrocolloids, 23, 616-618. 

Hunt, J.A. and Dalgleish, D.G. 1994. Effect of pH on the stability and surface composition in emulsions made with whey protein isolate. J. Agric. Food Chem. 42, 2131-2135. 

Low molecular mass surfactants are not needed in an ice cream mix to stabilize the fat emulsion, due to an excess of protein and other amphiphilic molecules in solution. If a mix is homogenized without added surfactants, both the whey proteins and the caseins will form this new fat globule membrane, with the caseins contributing most of the adsorbed protein... 

Although whey protein concentrates possess excellent nutritional and organoleptic properties, they often exhibit only partial solubility and do not function as well as the caseinates for stabilizing aqueous foams and emulsions (19). A number of compositional and processing factors are involved which alter the ability of whey protein concentrates to function in such food formulations. These include pH, redox potential, Ca concentration, heat denaturation, enzymatic modification, residual polyphosphate or other polyvalent ion precipitating agents, residual milk lipids/phospholipids and chemical emulsifiers (22). 

It is likely that the inability of whey proteins to function as well as caseinate in stabilizing foams and emulsions is due to conformational and structional differences in the two proteins. 

It is therefore postulated that whey proteins, which lack an amphiphilic conformation, do not orient sufficiently well at air/ water interfaces to stabilize foam or emulsion systems as effectively as caseinates. 

The WPC (0.2 - 7 stabilized emulsions have the lowest protein load ( 1.5 mg/nr) at fat surface areas between 1.0 and 3.0 nr/ml, whereas at larger surface areas, the soy protein (0 - 7) stabilized emulsions have as low values as those stabilized with WPC (0.2 - 7). It is interesting to note that an increase in ionic strength to 0.2 M NaCl does not increase the amount of protein adsorbed in the case of the whey proteins. In fact the opposite is observed, in contrast to the behavior of the other two proteins. 

In protein-stabihzed foams, protein flexibility is critical to the molecule functionality in stabilizing interfaces (Hailing 1981 Lemeste et al. 1990). This has important consequences in the development and stability of dairy foams and emulsions, where the heat treatment received by the material can define its foamability and dispersion properties. A symbiotic effect between native and denatured proteins on the emulsifying properties of whey proteins isolate blends has been observed by (Britten et al. 

An alternative to the traditional O/W/O or W/O/W emulsions is the O/W/W format. The addition of a whey-protein oil-in-water stabilized emulsion to an aqueous two-phase system (comprising heat denatured whey protein and high methoxy pectin) resulted in the formation of such an emulsion. This was subsequently gelled with calcium ions. It has been suggested that these novel structures can provide both encapsulation and controlled release (Kim et al. 2006). 

Improved stability of lipophilic bioactives may be obtained by tailoring the interfacial membranes of oil droplets. Rosenberg and Lee (2004) coated a primary whey protein-based oil-in-water emulsion containing paprika oleoresin (as the model core) with calcium alginate to enhance the stability and control the core release. 

Vitamin Bi was entrapped in an inner aqueous phase of a double emulsion stabilized by a mixture of whey protein isolate and xanthan as the external gum. The release of the vitamin was modulated by altering the pH or the ratio of the two biopolymers. The increased rate of release of the vitamin as pH was increased from 2 to 7 has been attributed to the decreased electrostatic interaction between whey protein isolate and xanthan. Increasing the rigidity of the external interface by increasing the amount of xanthan also decreased the rate of release of the vitamin (Benichou et al. 2004). 

Demetriades, K., Coupland, J., and McClements, D. J. 1997. Physical properties of whey protein stabilized emulsions as related to pH and NaCl. J. Food Sci. 62 342-347. 

Dickinson, E. and Yamamoto, Y. 1996a. Viscoelastic properties of heat-set whey protein-stabilized emulsion gels with added lecithin. J. Food Sci. 61 811-816. 

---