Caseins rheological changes

Abbasi, S., Dickinson, E. (2002). High-pressure-induced rheological changes of low-methoxyl pectin plus micellar casein mixtures. Journal of Agricultural and Food Chemistry, 50, 3559-3565. 

Thermodynamically unfavourable interactions between two biopolymers may produce a significant increase in the surface shear viscosity (rf) of the adsorbed protein layer. This change in surface rheological behaviour is a consequence of the greater surface concentration of adsorbed protein. For instance, with p-casein + pectin at pH = 5.5 and ionic strength = 0.01 M (Ay = 2.6 x 10 m3 mol kg-2), the surface shear viscosity at the oil-water interface was found to increase by 20-30%, i.e., rp = 750 75 and 590 60 mN s m-1 in the presence and absence of polysaccharide. These values of rp refer to data taken some 24 hours following initial protein layer formation (Dickinson et al., 1998 Semenova et al., 1999a). 

The viscosity of milk and creams tends to increase slightly with age, due in part to changes in ionic equilibria. Heating skim milk to an extent that denatures most of the whey proteins increases its viscosity by about 10%. Homogenization of whole milk has little effect on its viscosity. The increase in the volume fraction of fat on homogenization is compensated by a decrease in the volume fractions of casein and whey proteins because some skim milk proteins are adsorbed at the fat-oil interface. Pasteurization has no significant effect on the rheology of whole milk. 

Stabilizer, at pH 4. Addition of the CMC significantly reduced the droplet size, prevented aggregation, improved the release rate, and changed the rheological behavior of the multiple emulsion. The second multiple emulsion, stabilized by sodium caseinate-dextran, was also found to be an improved multiple emulsion. The droplet sizes were smaller with a more narrow size distribution when the conjugated sodium caseinate and dextran were used (compared to multiple emulsions stabilized solely by casemate). 

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