Does fat-free milk need to be homogenized?

No, fat-free milk doesn't need to be homogenized. When fat is present, it coats the globules of fat and proteins, preventing clumping. In fat-free milk, the fat is removed, so there are no fats coating the proteins, which will form a milky film at the top of the jug if it is left to sit. Homogenization prevents the formation of this milky film by physically breaking up the protein clumps and distributing them throughout the milk.