Dissolution and reconstitution of casein micelle containing dairy powders by high shear using ultrasonic and physical methods

• High shear greatly accelerates solubilization of otherwise insoluble dairy powders.
• Shear breaks powder agglomerates and helps release casein micelles into solution.
• Shear does not affect casein micelles or whey proteins during powder solubilization.
• Ultrasonication, rotor–stator mixing or high pressure homogenization can be used.
• Homogenization was the most and rotor–stator mixing the least effective.

The effect of shear on the solubilization of a range of dairy powders was investigated. The rate of solubilization of low solubility milk protein concentrate and micellar casein powders was examined during ultrasonication, high pressure homogenization and high-shear rotor–stator mixing and compared to low-shear overhead stirring. The high shear techniques were able to greatly accelerate the solubilization of these powders by physically breaking apart the powder agglomerates and accelerating the release of individual casein micelles into solution. This was achieved without affecting the structure of the solubilized proteins. The effect of high shear on the re-establishment of the mineral balance between the casein micelles and the serum was examined by monitoring the pH of the reconstituted skim milk powder after prior exposure to ultrasonication. Only minor differences in the re-equilibration of the pH were observed after sonication for up to 3 min, suggesting that the localized high shear forces exerted by sonication did not significantly affect the mass transfer of minerals from within the casein micelles.