Temperature changes are a major reason the dent exists. Milk travels through different environments before reaching your refrigerator — from warm loading areas to chilled trucks, then into grocery stores and finally into a home kitchen. As temperatures shift, the liquid inside expands and contracts. Without a flexible area to absorb that pressure, the jug could swell, crack, or burst if the milk freezes and expands. The indentation is designed to flex outward when pressure rises and return to its original position once the temperature stabilizes. This small feature helps the jug withstand everyday conditions during shipping and storage.
