Transportation Practices
Transportation and Storage
Finished fresh produce should be stored and transported under conditions that will protect the food against physical, chemical, and microbiological contamination. We recommend, if feasible, that raw whole produce not be stored with finished product and finished product be transported in clean, sanitary vehicles. We also recommend the following practices:
Keeping finished products refrigerated at temperatures appropriate for the product during storage, transportation, and display for sale to minimize the potential for growth of microbial pathogens
Equipping refrigerated transportation vehicles and storage rooms with accurate temperature measuring devices, preferably including a temperature recording function
If a recording temperature device is not used, we recommend that a min/max thermometer, i.e., a thermometer that shows the range of temperatures attained over a set time period, be used.
Shipping fresh-cut produce products on a FIFO basis to minimise storage time
Ensuring that the equipment in refrigeration vehicles is designed to circulate cold air uniformly throughout the vehicle while taking the load layout into consideration
Placing fresh-cut produce products in storage facilities and transportation vehicles in a manner that allows for proper air circulation
Transporting and storing fresh-cut produce products in vehicles and containers that are dedicated to carrying food products and have been treated by a process that is effective in destroying vegetative cells of microorganisms of public health significance
Inspecting transportation vehicles and containers for debris, soil, and off-odours prior to loading to increase their suitability for transporting fresh-cut produce
Loading and unloading fresh-cut produce in a manner that minimizes the potential for damage and for microbial contamination
Most modern refrigerated trailers have enough refrigeration capacity to maintain the temperature of the chilled or frozen products they are designed to carry, but the refrigeration unit must be coupled with a pathway to distribute conditioned air around the load space.
Proper loading is the key to providing this pathway for conditioned air. The trailer in combination with the way the product is loaded into it must provide a pathway for conditioned air to surround the load and stop outside heat or cold from reaching the load. Without this pathway of conditioned air heat from the Sun, road and outside air will penetrate the walls of the trailer and warm chilled or frozen products. In the winter cold outside conditions can cause chilled products to freeze.
Having loads stacked too high blocks the air supply chute, the first step in the air pathway. A blockage here completely prevents air from traveling along the rest of the pathway leaving most of the load in danger of warming. If a load blocks the sidewalls and ceiling, the summer heat will warm all of the product touching these surfaces. blocking the air pathway along the walls and ceiling can cause damage to frozen or chilled products, for example, a truckload of lettuce being set at 3 degrees Celsius (39 Fahrenheit) may arrive at its destination with a majority of the product reading at temperatures closer to 10 degrees Celsius (50 Fahrenheit).
Likewise, incorrect loading in the winter months can have the opposite effect. With products in contact with walls and ceilings suffering from freeze damage.
Pre-loading checklist for Refrigerated Vehicles
Refrigeration unit operating properly?
Thermostat calibrated?
Refrigeration air chutes and ducts properly installed and in good repair?
Door seals in good condition?
Doors seal tightly when closed?
Walls free of cracks and holes?
Front bulkhead installed?
Floor drains open?
Inside of vehicle clean and odour-free?
Floor grooves free of debris?
Inside height, width, length adequate for load?
Load braces and other devices available to secure load?
Is the vehicle trailer pre-cooled (or pre-warmed)?
How to Load Properly
Poor loading can lead to products being rejected upon arrival at market and retail destinations. The goal of proper loading is to maintain a clear pathway around the load to allow refrigerated air to absorb heat entering from the outside. The chute is the first step in the pathway, it delivers air to the entire top of the load.
The chute must be in good condition, if you see any holes patch them before loading. A chute in poor condition will not spread air evenly over the load and may result in hot spots. If the chute has become detached from the ceiling reattach it. Load only up to the chute, do not allow boxes to crush or even touch the chute.
Next, the air must spread out over the top of the load. Allow adequate room for the air to move from the chute to the walls and rear door. Do not allow an extra high load to block the air as it travels to the walls and rear door. A few extra boxes on the top of the load may prevent cold air from circulating to the walls and rear of the trailer. Provide adequate headspace so that the air may continue its path down along the rear door.
The ideal load pattern provides the needed three-inch gap between the boxes and the rear door. It is properly braced with a loading gate to guarantee that the boxes do not shift back against the door. Load bars can also be used to stop the boxes from shifting.
Next, the refrigerated air moves down a path between the load and the sidewalls. If the trailer has ribbed walls you can load against the walls. The ribs form an air path down the walls. Unfortunately, 95% of the trailers in use today have smooth walls.
Some strawberry shippers use this method to keep palletised loads braced away from the walls. Styrofoam blocks are held in place with short sticks that are placed between the boxes. Blocks are attached before loading.
If the trailer is wide you can build an air path down the middle of the chilled load as well as along the walls. Airbags should be used to stabilise a chilled load with a central pathway. Frozen products should be centre loaded and braced away from the smooth walls.
If there is not enough width for paths along both walls and in the load, use only the wall paths as they are far more important than the load path.
Next, the air must begin its return to the refrigeration unit along the floor. Special deep channelled floors have enough open area for the air to return to the refrigeration unit. Shallow duct floors do not have an adequate open area for proper airflow do not load directly on a shallow duct floor.
Chilled loads should be placed on pallets or specially built floor racks. Some shippers have successfully transported frozen products on slip sheets.
Be sure the floor is clean, a little trash can completely block the path of the air along the floor. Load dividers are sometimes used in mixed loads, they should not drop all the way to the floor otherwise they will block the floor air path. Hand stacked boxes can also cause the same problem. Never hand stack on the floor if pallets are needed to provide an air path.
The final step in the air path around the load is the front bulkhead. This keeps the load from shifting against the front wall and blocking the air returning along the floor and walls. Products can be loaded directly against a solid bulkhead but if the trailer does not have a solid bulkhead make a temporary one out of pallets or special racks. Make sure the bottom board of the temporary bulkhead does not touch the floor and block the floor air path.
Remember proper loading requires a clear path for refrigerated air to flow around the load. The path is achieved with:
An open chute in good condition
Loading that allows adequate and uniform headspace
Properly bracing the load away from the rear door
Bracing the load away from the sidewalls
Making sure the floors are clean
Not placing product directly on shallow duct floors
Using pallets to make a temporary bulkhead if the trailer does not have one
Finally, frozen products should never be left on a dock that is warmer than the necessary temperature conditions. Chilled products can quickly warm if they are left out in the open, never leave them on an open dock, only load products that are at proper shipping temperature.
Tell your supervisor about any obvious trailer problems like damage to walls, broken door seals, odours from previous loads, and missing air chutes. Trailers should be thoroughly precooled before being loaded and the trailer doors opened only just before loading begins.
The refrigeration unit must be turned off when the trailer doors are open, if it is left on, ice may build up on the refrigeration coil.
Follow the recommended loading practices and you will have done your part to ensure that the product will arrive at its destination in good market conditions.
Pre-trip Inspection
The journey that fresh produce undergoes to go from farm-to-fork can be thousands of kilometres and involves a highly coordinated series of actions from many involved. To preserve product quality the ideal temperature has to be controlled and kept throughout all storage and distribution activities. In other words, a cold chain needs to be maintained, linking farm and fork. A cold chain is only as good as its warmest link.
Keeping the load temperature unchanged throughout transport and storage involves the product with all their chemical and biological processes linked to perishability, as every load requires specific temperature and humidity conditions. The post-harvest journey involves people who load, pack, transport and unload the goods as well as technology that ensures proper temperature conditions along the supply chain.
Before you start your journey make sure you perform a pre-trip inspection to minimise on the road operating problems and maximise product safety. Be sure to;
Confirm that your refrigeration unit is running smoothly
Make sure that the fuel tank is filled and that you have enough fuel to make your trip
Familiarise yourself with your load
Check the temperature before loading
Make sure that the trailer is precooled to the desired temperature to remove residual heat
Perform a defrost half an hour after loading to clear the evaporator coil and ensure maximum cooling performance
Inspect the trailer or truck for air leakage. Check the body for condensation when loaded to spot any possible body damage and thermal brakes in the insulation
Check that your doors are securely sealed before you start your trip
Verify the load temperature and the unit operation at least every four hours
