Dairies use high-pressure equipment to force the milk through fine openings. This breaks up the milk fat into tiny, well-dispersed globules that cannot recombine into larger fat globules because of their minute size and the movement of the water molecules in the milk. This anti-combining action is furthered by the milk's casein protein, an emulsifying agent. If the fat globules were allowed to combine, they would float upward to form a distinct layer over the fat-free milk.
** Asian Recipes