Can I pack frozen and refrigerated milk in the same cooler?

At Milk Stork, we understand the importance of keeping your milk at the right temperature to preserve its quality and safety for your baby. For this reason, our coolers are designed with precision and specific functionality in mind.

It is not possible to pack both frozen and refrigerated milk in the same cooler. Mixing frozen and refrigerated milk compromises the cooler’s ability to maintain consistent temperatures, risking the integrity of both frozen and refrigerated milk.

Milk Stork Pump, Freeze, and Stash coolers are designed to maintain the temperature of already refrigerated or frozen breast milk. They do not bring milk to frozen or refrigerated temperature, they simply maintain it. They do not use gel packs or dry ice, and there’s no need to refrigerate or freeze the cooling units prior to use.

Milk Stork refrigerated and frozen coolers use different technology therefore are not interchangeable.

The refrigerated (or Pump) coolers rely on the principle of evaporative cooling, continuously evaporating small quantities of water at low pressure over hours and days of operation. Water flow within the cooler is regulated – responding to ambient temperatures – which protects the cooler’s contents from external temperature fluctuations during shipping.

The frozen (or Freeze/Stash) coolers rely on high-performance vacuum-insulated panels that line the inside of the cooler to work off of the frozen breast milk placed inside the cooler that will maintain the frozen ambient temperature for 96 hours. Frozen coolers have to be completely filled in order to maintain the frozen temperature.

Why This Matters

Attempting to combine the two types in one cooler can result in:

• Thawing of frozen milk.
• Freezing of refrigerated milk.
• Overall temperature instability, potentially rendering your milk unusable.

What Should I Do?

If you have both frozen and refrigerated milk to ship, we recommend ordering separate coolers for each type. This ensures your milk is handled in the safest, most effective way possible.

We are here to support you and answer any additional questions about our shipping solutions. Feel free to reach out to our team