Keep refrigerated cargo safe

Keep refrigerated cargo safe

Salmonella-tainted eggs may have been the food safety headline of 2010, but in actuality, the FDA issued more than 330 food safety-related recalls, warnings and advisories last year on items from nearly every aisle of the supermarket.

"Whenever there is a large food recall in the news, it can serve as a reminder of the importance of maintaining the integrity of the cold chain," says Bill Maddox, applications manager for Carrier Transicold. "Goods can travel long distances from centralized growing and production centers, so refrigerated transport plays an increasingly important role.

“Today’s refrigerated trucks and trailers provide incredibly sophisticated capabilities for maintaining proper food safety, yet even the best refrigeration technology can’t completely assure the safety of cargo that has been improperly loaded,” he warns. “Adhering to a few simple best practices for loading will help safeguard product delivery.”

Think temp control before loading
Refrigerated cargo should always be loaded into a truck or trailer that has been pre-cooled to the proper temperature. Pre-cooling is very important because excess heat in the cargo space or walls could transfer to the product and raise its temperature.

Likewise, refrigerated cargo should be at its preferred temperature when loaded into the truck or trailer. Transport refrigeration units are sized to maintain the temperature of the load, not to change it. So if a pallet of product should be transported at 34˚ F, it should also be cooled to 34˚ F prior to loading.

“Care should also be taken to ensure product does not sit on an unrefrigerated dock for long, as loading it warm can ultimately create hot spots in the load,” says Maddox.

Go with the flow
Poor air distribution is a primary cause of cargo deterioration, even when refrigeration capacity is more than adequate. Airflow obstructions can result in hot spots and short cycling. To ensure proper airflow, maintain at least one to two inches of clearance from sidewalls and nine inches of clearance from the ceiling.

“If possible, use an air chute, a flexible duct that runs the length of the trailer above the cargo, to help provide uniform air distribution throughout,” says Maddox. “At the back end of the trailer, at least four inches of clearance should be left between cargo and the rear doors. And, although it seems obvious, never block the evaporator outlet.”

To maintain airflow underneath cartons, a channeled “T-floor” or pallets are recommended for single-temperature loads. In multi-temperature situations, such as with Vector 6600MT trailer or Supra 950MT truck units where sections of the cargo area are sealed off from each other and kept at different temperatures, pallets should be used to maintain airflow underneath.

Stop before you drop
During loading and deliveries, the temptation might be to run the refrigeration unit, but it’s best to temporarily shut it off. Shutting down the unit while the doors are open prevents a cascade of effects that can impair refrigeration integrity.

“When the reefer unit is left running, the unit fan can draw in warm humid air that will condense and freeze on the evaporator,” Maddox explains. “If enough of this humid air freezes, it will block the evaporator coil, which reduces the cooling capacity and will then cause the unit to go into frequent defrost modes, during which it will not be providing any cooling.

“By shutting off the refrigeration system, you save fuel and help assure the cooling mode is available when you most need it to keep the product at proper temperature,” he adds.

Adhering to sound practices such as these can do a load of good when it comes to ensuring safety of refrigerated goods in transit.

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