4 Things Every Shipper Should Know About Packing Refrigerated Freight

To load your freight correctly, it is helpful to understand how a reefer works to maintain the temperature of your shipment. Most reefers can maintain temperatures between -22°F and 86°F but there are some specialized units called super freezers that can hold temperatures as low as -94°F. Reefers can be either containers for ocean transport or trailers for over the road, but they both operate using a similar concept.

Once your freight is loaded, the specific temperature required is programmed into the reefer. It is important to note that a reefer is not designed to cool your products after they are loaded, so all freight should be pre-cooled before being packed.

To maintain the programmed temperature, two fans at the back of the reefer emit air which is pushed downward. The air then enters the specialized aluminum t-bar flooring, where it fills the space inside the unit and circulates around the cargo.

Consistent air flow is key to making sure that your refrigerated freight maintains the necessary temperature throughout transport. So, when packing your cargo, you want to make sure that air can move around it on all sides and there are no blockages that may prevent this movement. If blockages do occur, this can cause sections of your cargo to fall out of temperature regulations and possibly spoil.

While all cargo has packing guidelines specific to the commodity, there are some best practices that apply to all reefer loads.

1. Don’t fill the unit above the red line on the wall or beyond the red line on the t-bar flooring. These lines show the minimum distance your freight should be from these points to maintain adequate airflow for temperature control. The line on the wall shows how far your cargo must be from the ceiling and the floor line shows the distance you must keep from the door.
2. Always pre-cool your freight to the transport temperature before loading it onto the reefer. Reefers are meant to maintain the temperature of freight and don’t have the ability to raise or lower it, so your cargo must be at the proper transport temperature prior to packing.
3. Don’t turn the refrigeration unit on until the reefer is loaded and the doors are closed. Pre-cooling the reefer before loading can cause condensation and humidity when the cool air meets the ambient temperature outside. These conditions can be damaging to freight by causing mold, bacteria, and weakened packing material.
4. Cover any open floor space not containing cargo with cardboard or a similar material. Air will move in the path of least resistance. Since the cooling originates from the floor, air will circulate away from your cargo and into any empty space where the floor isn’t covered. By covering the floor, you guarantee that air won’t concentrate in these empty spaces and instead flows around your freight as it’s meant to.
5. Make sure your reefer and its contents are compliant with the Food and Drug Administration’s (FDA) Food Safety Modernization Act on Sanitary Transportation of Human and Animal Food. If you are shipping any type of food item, your transport operations must be compliant with the guidelines set by the FDA. In the Food Safety Modernization Act, there are two guidelines directly related to loading and transport of reefers:
   • Vehicles and Equipment: Make sure the container your goods will be shipped in is clean and dry. This includes inspecting for dirt and pests and making sure the refrigeration equipment is working before loading your cargo.
   • Transportation: Ensure that your fruits and vegetables will be maintained at the correct temperature during transit. Also verify that there will be no cross contamination between fresh produce, ready to eat foods, and non-food items when loading the truck.

Fresh produce must receive special consideration during transportation because it’s “living” cargo, meaning that it emits gases such as C02, water, heat, and ethylene while inside the reefer.

The presence of these gases means that a continuous flow of air and ventilation is especially important to maintaining quality of the produce. In addition to keeping the set temperature stable, the reefer also needs to be cycling out the air inside the container and replacing it with fresh air. Since these gasses can create condensation, you should also ensure that the reefer’s drainage openings are clear for excess water to flow out.

When packing fresh produce, it should be loaded on top of pallets and stored in containers with ventilation holes that align with each other for proper air flow.

These are some common temperature guidelines for different types of produce:

• 32-36°F: Greens, fruits and vegetables
• 38-40°F: cranberries and avocados
• 40-46°F: green beans, potatoes
• 45-50°F: bananas, tomatoes, cucumbers, watermelon, some citrus

For a more complete list of ideal transport temperatures for different produce, you can reference this guide from the Produce Blue Book.