To improve its shelf-life, milk undergoes a homogenization process. This process produces fat globules of a uniform, small size. During the homogenization process the size range of the fat globules is reduced from 0.1-15 μm in unprocessed milk to 1-2 μm in homogenized milk . These smaller globules cannot form large enough clusters for creaming to occur, increasing the shelf-life of the milk.
The creaming process is governed by Stokes’ Law and the relative densities of the fat and the other fluid components of the milk. Milk also contains casein micelles, in the size range of 0.05-0.25 μm. The micelles play a role in stabilizing the fat globules, especially after the homogenization process. The size of the fat globules and the proportion of free casein micelles are important parameters for monitoring the homogenization process and can be measured simultaneously by laser diffraction.