1. Controls Internal Pressure
Milk reacts to temperature changes. As it moves from warm delivery trucks to cold refrigerators—or if it’s accidentally left in freezing conditions—the liquid can expand or contract. The circular dent acts as a flexible pressure point, allowing the jug to adjust safely.
If the jug didn’t have this feature, pressure changes could cause the plastic to warp, crack, or even rupture. In simple terms, the dent works like a built-in pressure release.
