Transportation Practices
Produce must often be transported as part of fresh handling, whether from the field to the packinghouse, from the packinghouse to the storage facility, or to various destination markets. During transport, produce must be stacked in ways that minimise damage, then be braced and secured. An open-air vehicle can be loaded in such a way that air can pass through the load, and provide some cooling of the fresh produce as the vehicle moves. Travelling during cooler hours (night and early morning) can reduce the heat load on a vehicle that is transporting produce.
Refrigerated transport is highly recommended for most perishable horticultural produce. Temperature management is especially critical during long-distance transport, and proper airflow is the most important factor in ensuring that the load stays cool. Loads must be stacked to enable proper air circulation to carry away heat from the produce itself as well as incoming heat from the atmosphere and off the road. Transport vehicles should be well insulated to maintain cool environments for precooled commodities and loads should be braced away from the sidewalls and back door of the trailer.
Average road temperatures can be much higher than air temperatures during hot months of the year, averaging 22°C (40°F) higher readings than the air temperature average. This makes it difficult for refrigerated vehicles to maintain the recommended temperatures. Transit times under these conditions should be as short as possible since deterioration will increase as temperatures increase.
Mixed loads can be a serious concern when recommended temperatures are not compatible (for example, when transporting chilling sensitive fruits with commodities that require very low temperatures). Try to avoid this situation, since either some of the fresh produce will be injured by chilling or some of the fresh produce will deteriorate more quickly than when handled at the recommended low temperature and your investments in post-harvest handling technologies will largely be wasted.
Another problem arises when ethylene producing commodities and ethylene sensitive commodities are transported together. High ethylene producers (such as ripe bananas, apples, cantaloupe) can induce physiological disorders and/or undesirable changes in colour, flavour and texture in ethylene sensitive commodities (such as lettuce, cucumbers, carrots, potatoes, sweet potatoes). Using ethylene scrubbers installed in the vehicle can reduce this problem during transport.
General Dos and Don’ts for Transporting High-Quality Produce
Do NOT overload vehicles.
Prevent compression damage to produce by avoiding over-filling of containers (rounded sides or bulge-packing) and stacking heavier produce at the bottom of the load.
Use strong packages (half the stacking strength of a corrugated fibreboard container can be lost during a five day trip in a high humidity environment).
Avoid rough handling during loading and unloading.
When stacking containers, be sure to align them properly (most of the strength of a corrugated box is in the corners). A one-inch overhang will decrease stacking strength by 15 to 34%.
Prevent vibration damage by using air suspension systems - these will provide a more gentle ride during transportation.
Using suitable trays, place packing, use of plastic bags, container liners, or placing a soft pad at the top of a full box can reduce vibration damage.
Make sure the vehicle has adequate ventilation to prevent heat gain during transport.
Check to ensure the vehicle is free from food safety hazards such as spilled fertiliser, animal manure, blood, or odours.
Use a preloading checklist to ensure the vehicle is ready to use successfully.
Ensure the vehicles are well-insulated and have doors with secure, tight seals.
Run through the checklist for refrigerated transport before handling each load.
Look for recommended design features when purchasing new or used transport vehicles.
Precool refrigerated vehicles to suit fresh produce requirements.
Load only precooled produce into vehicles from a refrigerated dock.
Do NOT allow delays when loading on an open dock - delays will cause heat gain, especially if fresh produce is exposed to full sun.
Turn off the refrigeration unit while loading from an open dock (leaving the unit on may cause ice to form on the refrigeration coils, blocking air circulation).
Use high quality vented containers and load fresh produce to ensure adequate air movement throughout the load to remove the heat generated by produce respiration.
Do NOT block airflow under or anywhere else in the load.
Monitor the supply air temperature and the return air temperature for obtaining the best performance of refrigeration units.
Avoid mixed loads if possible; or install ethylene scrubbers to prevent damage to ethylene sensitive commodities.
Do NOT transport chilling sensitive commodities when thermostats are set below 12°C (53°F)
Load produce away from side walls to prevent heat gain from the external environment.
Make sure mixed sizes of containers or non-palletised produce does not block lengthwise airflow.
Do NOT turn off the refrigeration unit during delays in transport.
Brace the load at least 5 cm (2”) away from the sidewalls and at least 10 cm (4”) away from the rear door.
Use a portable temperature recorder to verify temperature management.
