Steady shear rheological properties of micellar casein concentrates obtained by membrane filtration as a function of shear rate, concentration, and temperature.

The use of casein preparations obtained by membrane separation is receiving increasing interest from the dairy and food industry. The objective of this work was to generate information about the steady shear rheological properties of micellar casein concentrates (MCC) and the effect of composition, temperature, and shear rate on these properties. Micellar casein concentrate preparations with 2 levels of serum proteins (SP; 65 and 95% SP reduced, respectively), were obtained from skim milk by microfiltration followed by spray drying. Micellar casein concentrate preparations with casein concentrations ranging from 2.5 to 12.5% were obtained by dispersing the MCC powders in ultrapure water. Steady shear rheological analyses at temperatures ranging from 0 to 80°C were performed using a strain-controlled rheometer. Viscosity versus shear rate curves were used to evaluate the effect of shear on viscosity, and the apparent viscosity at a shear rate of 100 s(-1) was used to make direct comparisons between various concentration and temperature conditions. The 65% SP-reduced MCC had lower viscosity than the 95% SP-reduced MCC at the same casein concentration and temperature. Protein preparations at casein concentrations above 7.5% displayed shear-thinning behavior, which was more pronounced as concentration increased. The viscosity of MCC increased exponentially with casein concentration and decreased with temperature. The dependency of viscosity on temperature followed an Arrhenius relationship. A modified Arrhenius model able to accurately predict rheological properties under desired shear, temperature, and concentration conditions was developed and validated. This study provides critical rheological data necessary for developing practical applications of micellar casein preparations.