StePac:
Crate and carton design more important than you think
Crate and carton Manufacturers often don’t have the post-harvest expertise required to fully understand the role that design plays in protecting and preserving fragile fruits and vegetables.
Therefore it is vital that growers and packers provide their input during the design process. Ivo Tunchel, StePac’s South America Territory Manager, has many years of experience helping growers and packers improve their post-harvest practices. He believes that the major factors listed below should be taken into consideration when designing and choosing produce crates/cartons:
•Type of produce
•Cooling method used
•Pallet construction
•Transport methods
If crates/cartons are not properly designed for the size and shape of the produce inside, skin damage may occur. In particular, when using plastic crates special attention should be paid to the size and shape of the vent holes and the smoothness of the edges.
Box manufacturers are experts at taking these factors into consideration, but it is essential that packers provide them with accurate information that includes worst case scenarios.
Incorrect calculations can have costly consequences, endangering the integrity of the pallet structure and damaging the produce. Receivers of fresh produce are likely to charge for repalletizing and therefore cutting costs on carton strength (fig 4) can prove more expensive!
Air flow
Boxes should be designed to allow for adequate air flow, which together with cooling
requirements are produce dependent. Insufficient air flow across cartons containing climacteric produce for instance may result in local temperature increases and build up of ethylene. On the other hand high air flow can result in excess dehydration of certain produce items.
The use of plastic liners impedes air flow and a carton that is well designed with sufficient ventilation for non-bagged produce may be unsuitable for bagged produce. For instance, bags will block vent holes in the base of the cartons, making them unnecessary.
When liners are used, the best solution is the use of open top cartons with large openings at the top centre of all four sides of the box, (fig 5). It is important the vents on adjacent cartons on the pallet are aligned. This solution enables unrestricted air flow across the pallets along both axis and optimum ventilation of both bagged and non-bagged produce.
Pallet construction
During the design phase, carton configuration on the pallet should be studied, as this can significantly affect air flow.
Cooling method used
The type of material used and the ventilation design is also dependent on the method of cooling.
Hydro-cooling: Wooden crates, corrugated plastic cartons (fig 10) and waxed cartons may be used.
Forced air cooling: Wooden crates, corrugated plastic cartons, non-waxed cartons. Unobstructed air flow across the pallet is critical.
Passive cooling in Cold chambers: Wooden crates, corrugated plastic cartons, non-waxed cartons. Ventilation design should take into consideration that incoming cool air is passively circulated within the chamber. Ventilation holes must be relatively large to allow heat of respiration from the pallet centre to escape as quickly as possible.
Vacuum cooling: Wooden crates, corrugated plastic cartons, non-waxed cartons.
Ice packing: Wooden crates, corrugated plastic cartons, waxed cartons. Special attention should be paid to the size of the vent holes so that ice doesn’t fall out during transport.
Summing it all up
Working closely with carton/crate manufacturers to design the best carton/crate for your needs can reap significant rewards. While carton/crate designers typically focus on price and graphic artwork, your insights about handling, cooling/refrigeration and ventilation will ensure that your new box serves you well, effectively protecting and preserving your perishable cargo.
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