The circular dent on the side of a milk jug isn’t just a random desig — it actually serves several important purposes:
1. Safety in Case of Pressure Build-Up
If the milk is exposed to heat or starts to spoil, gases can build up inside the jug. The dent acts like a pressure release area — it can expand outward to prevent the jug from bursting or cracking.
2. Shock Absorption
If the jug is dropped, the dent helps absorb the impact and reduces the risk of the plastic breaking or the milk spilling.
3. Volume Flexibility
Milk expands and contracts with temperature changes. The dent allows the plastic to flex without damaging the container.
4. Spoilage Indicator
If you notice the dent is puffed out, it could mean that gas has built up inside — a possible sign that the milk has spoiled.