Transport practices for melon
Transport of melons generally takes place in (refrigerated) trucks, reefer containers, or by plane. Checks and proper loading are always important to maintain good (temperature) conditions for the product during transport. For fresh products, like melon, refrigerated transport is often necessary. Trucks and reefers can maintain a low temperature, but do not have enough cooling capacity to lower the product temperature. Therefore, products must be pre-cooled before entering the refrigerated truck or reefer. During transport and waiting periods, the load must be well covered to protect against dust, sun and rain. Careful driving and handling are essential to prevent damage to produce from mechanical actions.
Optimal transport conditions
Transport of melons from the field to the packhouse should follow soon after harvest because it is essential that melons, especially for overseas shipment, are cooled as soon as possible. After cooling in the packhouse, they can be transported further in refrigerated trucks or reefer containers. The best transport temperature for melons depends on variety, maturity and transport time. For example, it is usually in the range of 3-5 °C for cantaloupe types, and 8-12 °C for honeydew types and watermelon. The optimum humidity would be around 90-95% RH. The temperature during transport should be kept constant to reduce condensation. Higher humidity or condensation may encourage the growth of moulds.
Attention points during loading and transport of melons
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Loading a truck with harvested melons. Photo by WUR. Loading at the field
Upon pick-up, the crates or other packaging must be stacked carefully and tightened to ensure they do not shift or fall-over during transport. In the case of larger trucks and loads that do not fully occupy the truck floor, the tightening must be done by placing (pallet-)edge protectors at the edges of a batch of stacked field crates. Especially for warm loads (picked up at harvest), air ventilation through the stacks should be warranted. -
Melons being unloaded at a 'cold tunnel' dock. Photo by WUR. Loading after pre-cooling
The loading must be realized preferably from a climate-controlled loading dock via “cold tunnels” into the truck or reefer. This prevents ambient air from entering the pre-cooled reefer container, truck, or the climate-controlled loading dock. Apart from maintaining the melons at the desired low temperature, this is important in order to avoid condensation, which will occur when warm moisture-laden air enters the reefer container or truck. -
Do not stow above the red line in a reefer container. Photo by WUR. Stacking of refrigerated truck and reefer
In reefer containers, with bottom-air delivery system, the cargo must be stacked as a solid block with only little space between the cartons and the reefer container wall to avoid short–cycle airflow. Also do not stow above the red line at the reefer wall. Do not use wraps or anything else that is detrimental to good airflow. -
Temperature logging is key to check for maintaining an unbroken cold chain. Photo by WUR. Temperature logging
The cold chain should not be broken, the product remains best in the set temperature range, which depends on variety and maturity. Lower or higher temperatures can easily lead to loss of quality. Cooled melons that are re-warmed when the cold chain is broken, can have condensation on the skin. This will increase their susceptibility to fungal decay. Good quality control during transport includes temperature logging. -
Moving pallets with melons to a cold storage room. Photo by WUR. Unloading
Unload the cargo carefully to avoid handling damage. The pallets (or other packaging) with melons must be moved directly to a cold storage room. It is recommended to sample fruits for inspection at this moment. Visual appearance of melons, but also of packaging and pallets can be documented via photographs.
"A reefer container or truck is only capable of maintaining the produce temperature, not to lower it. Therefore, products need to be pre-cooled."