Answer: The lower temperature reduces molecule speeds, reducing the number of effective collisions.
Almost all food spoils. Most of the spoilage is because of the enzyme activity of microorganisms. Bacteria, which is an example of microorganism, grows rapidly at room temperature or higher temperatures mainly ranging between 40 degrees F to 140 degrees F.
The most commonly used strategy to minimize the rate of food spoilage is to keep it in a cool environment i.e. by refrigerating it. The lower temperature provided to the food slows down the movement of molecules and the number of collisions between them, thus slowing down the rate of enzyme activity.