It’s the beginning of November, and you are preparing a shipment of freshly harvested apples for delivery to a grocery retailer. Since apples are temperature-sensitive, you’ve loaded them into a reefer (refrigerated trailer or container) for transport. But upon arrival, the grocer is met with a truckload of softened apples. What went wrong?
A successful cold chain shipment requires much more than a reefer set to the correct temperature. How you pack your goods into the reefer also plays a significant role in ensuring they arrive intact.
And not all loads can be packed the same. Depending on the commodity you’re shipping, there are specific guidelines and considerations for how it should be arranged in the trailer for successful transport.
Below, we share 4 things you should know about packing your refrigerated freight so it doesn’t experience the same fate as the florist’s regrettable roses.
1. Understand How a Reefer Works
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.
2. Universal Reefer Loading Guidelines
While all cargo has packing guidelines specific to the commodity, there are some best practices that apply to all reefer loads.
- 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.
- 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.
- 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.
- 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.
- 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.
3. How to Pack Fresh Produce
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.
4. Packing Methods for Chilled, Frozen, and Specialized Freight
Most refrigerated freight is separated into one of 3 categories based on transport temperature: chilled, frozen, and specialized.
Transport temperature: above freezing (32°F or 0°C)
Common examples of chilled freight are meat, seafood, beverages, confectionaries, and plants. This type of cargo has the same packing requirements as produce because it requires adequate airflow on all surfaces to maintain the set temperature. Chilled cargo should be in packaging with uniform ventilation holes and stacked on pallets.
Transport temperature: below freezing (less than 32°F or 0°C)
Common examples of frozen freight are ice cream, frozen produce, frozen meat, frozen seafood, and frozen prepared foods. This type of cargo should be stowed in a block stowage formation, where there are no gaps between the boxes and pallets. There should be no ventilation holes in the packaging for this cargo.
Transport temperature: varies based on commodity
Specialized refrigerated freight are items that require additional consideration when transporting because of their sensitive nature. Examples of specialized freight include tobacco products, pharmaceuticals, film, photo equipment, and industrial or hazardous chemicals.
Due to their high sensitivity to any environmental changes, temperature and humidity must be closely monitored when moving these commodities. Handling and temperature information should be obtained from the manufacturer. Since these items are highly regulated, you should also check handling and transportation standards from the industry’s governing body to ensure you maintain compliance.
Packing For Successful Transport
Now that you know how to successfully pack your refrigerated freight, what do you think went wrong with the wilted apple delivery? If the reefer temperature was set correctly, improper packing could have easily been to blame. Since apples are chilled freight, there is a good chance there was not correct ventilation in the packaging, creating humidity that caused the fruit to begin going bad.
While this is a hypothetical situation, you can avoid real life complications with your refrigerated freight by ensuring that they are packed for successful transport.
Need help with your cold chain strategy? Our cold chain experts look forward to helping you create a personalized solution for your refrigerated freight, from loading to delivery.