Why Smaller Fat Droplets Stay Mixed
Milk is not a true solution: its fat is dispersed through water as tiny droplets. Because fat is less dense than the watery part of milk, larger droplets gradually rise, gathering into a cream layer. Homogenization changes the size of those droplets, not the amount of fat in the milk.
In the homogenizer, milk is pushed through a narrow opening under pressure. The intense flow and turbulence break many fat globules into much smaller ones. Small droplets rise far more slowly than large ones—the slower movement lets ordinary handling and storage keep the milk looking evenly mixed.
The New Droplets Need a Stable Surface
Breaking droplets apart creates much more total surface area. Proteins in the milk attach to the newly exposed fat surfaces, helping keep the droplets from joining back together. This makes the dispersion more stable, though the fat has not dissolved into the liquid.
That distinction explains the visible difference: unhomogenized milk can form a layer of cream as its larger fat globules rise, while homogenized milk stays more uniform in the carton. Homogenization also makes cream harder to skim off later, because the fat is spread through the milk as a vast number of tiny droplets rather than concentrated at the top.
