4. Tamper or Expansion Indicator
In some cases, if the circular dent is bulging outward before opening the jug, it may be a sign that the contents have spoiled or undergone fermentation. It can act as an early warning system. The pressure created by gas buildup (from bacteria or spoilage) can push the dent out — a signal not to drink the milk.
Conclusion
So, next time you grab a gallon of milk from the fridge, take a second to appreciate that little circular dent. It’s a smart design element that helps regulate pressure, absorb impact, reinforce the structure, and even alert you to possible spoilage. It’s just one of the many hidden features in everyday items that make our lives a little easier — and a lot less messy.
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