ANSWER

Sodium caseinate is amphiphilic and shows good emulsifying properties of fat. It contributes to opacity, solubility, heat stability as well as superb water and fat-binding characteristics that make them suitable as emulsifiers. Sodium caseinate is a better emulsifier than whey proteins as it has a more hydrophobic and flexible molecule that reduces surface tension faster and to a greater extent (Onwulata, 2005).

According to Hogan et al., (2001), emulsions are prepared with 5% (w/v) solutions of sodium caseinate and soy oil at oil-protein ratios of 0.25−3.0 by homogenization at 10−50 MPa. Emulsions are then spray-dried to yield powders with 20−75% oil (w/w). Emulsions made with Na-caseinate will produce particle sizes that are below 1µm of fat; with protein ratios as high as 60:1 (0.16%, w/w Na-caseinate). A lower concentration of sodium caseinate (0.33%) compared with milk protein isolate (1.26%) is sufficient to stabilize a 10% fat emulsion (Vega et al., 2007).

The encapsulation of stabilized emulsions of sodium caseinate would greatly improve with the presence of lactose. Powder surface fat is reduced from 30% to <5% when lactose is added at a 1:1 ratio to sodium caseinate in an emulsion containing 30% (wt/wt) oil (Vega & Roos, 2006).

The conformation of casein greatly affects the initial emulsion stability and resistance to shear (Vega et al., 2007). The more the solution is concentrated in sodium caseinate, the more efficient the encapsulation will be. However, the fat and caseinate ratio is correlated with the emulsion’s physical properties. Excess sodium caseinate acted more as a filler in the encapsulating matrix than as a surface-active element in the emulsions (Vignolles et al., 2007).

References

Hogan, S. A., McNamee, B. F., O’Riordan, E. D. & O’Sullivan, M. (2001). Microencapsulating Properties of Sodium Caseinate. Journal of Agricultural and Food Chemistry, 49(4), 1934-1938. https://doi.org/10.1021/jf000276q

Onwulata, C. (2005). Encapsulated and Powdered Foods (pp. 480-482). Boca Raton: CRC Press.

Vega, C. & Roos, Y. H. (2006). Invited review: spray-dried dairy and dairy-like emulsions – compositional considerations. Journal of Dairy Science, 89(2), 383-401. https://doi.org/10.3168/jds.s0022-0302(06)72103-8

Vega, C., Goff, H. D. & Roos, Y. H. (2007). Casein molecular assembly affects the properties of milk fat emulsionsencapsulated in lactose or trehalose matrices. International Dairy Journal, 17(6), 683-95. https://doi.org/10.1016/j.idairyj.2006.08.004

Vignolles, M., Jeantet, R., Lopez, C. & Schuck, P. (2007). Free fat, surface fat and dairy powders: interactions between process and product. A review. Le Lait, 87 (3), 187-236. https://doi.org/10.1051/lait:2007010