What surrounds the fat globules in raw milk to prevent rancidity?

The protective membrane surrounds fat globules in raw milk and plays a crucial role in maintaining milk quality. This membrane is composed of proteins and lipids, which help stabilize the fat globules and prevent them from coalescing. By keeping the fat in a dispersed state, the protective membrane also helps to inhibit the action of lipases, enzymes that can break down fats and lead to rancidity. As a result, the milk remains fresh and palatable for a longer period.

The other options, while related to aspects of milk quality, do not specifically address the mechanism of preventing rancidity through the stabilization of fat globules. Calcium caseinate is a protein that contributes to the overall quality of milk but does not directly protect fat globules. Pasteurization is a process that destroys pathogens and extends shelf life but does not create the membrane. A cooling system helps maintain milk freshness by reducing bacterial growth but does not interact with the fat globules in the same way.